SUSREF - Construction IT research at VTT

SUSREF3 (46)Figure 2.: Contribution of the individual construction element to the environmental impacts of theuse phase according to the zone and building (weighted average). Where Z1, Z2 and Z3,represent European south , central and northern climatic zones, and “_N” represents the newbuildings. (Source: ImproBuilding Eur 23493 EN_2008)According to the previous figure, old Nordic low rise buildings have the highest energydemands per square meter. Highest losses are across exterior walls, roof and ventilation.Lowest values are related to southern new high rise buildings, where external area/volumerate and indoor –outdoor temperature differences are the lowest. In high rise, roof loses don’tcontribute significantly to energy demand, and major loses are related to ventilation, exteriorwalls, and windows.Therefore, and though SUSREF project is aimed at improving external walls, for low risebuildings, improving external wall will have not have the expected heating reduction, if roofand basement remain untouched. For high rise, besides external walls and windows,ventilation contributes significantly to the energy demand.Improving thermal insulation in warm and humid regions does not result in the same energysavings as in a moderate climate. The same holds for the moisture response of theconstruction and indoor air quality. In central Europe, condensation in winters occurs on theinterior surface of windows, whereas in hot and humid climates when air conditioning is used,it may occur on the outside part. Therefore, it can be stated that there is not an uniquesolution for all the climates.Ventilation is required to keep indoor air in good conditions and avoid moisture relatedproblems, and therefore a certain number of air changes per hour needs to be guaranteed.The air changes required will depend on the activity and the occupancy level in the dwellingbut conditioning this air to indoor set points it is an energy intensive activity, 0.34Wh areneeded to raise a cubic meter of air by 1ºC. This leads to 1 kWh energy consumption to raise10 ºC outdoor fresh air temperature for a100 m 2 floorplan dwelling to achieve one air changeper hour. The higher the temperature difference, floor area or number of air changes, thehigher the energy demand to heat this air, and the higher buildings energy consumption willbe at the end.Therefore, a low-energy ventilation system should reconcile two opposite requirements: anadequate air flow for satisfactory indoor air quality and a minimal air flow to reduce energyconsumption.

SUSREF4 (46)This deliverable tackles the issues relevant to achieving a good indoor air quality andminimising buiding energy consumption through different wall refurbishment concepts.2.1.1 Refurbishment practices and energy demand reductionExternal walls represent a large proportion of the heat losses for high rise, multirise and forsingle family, and thus represent one of the key parts of those elements of the building withhigher potential to reduce energy consumption. There are several refurbishment practices forwalls, but depending on local circumstances or limitations (legal, ownership, aesthetics,economics, climate….) not all of them will be applicable.SUSREF has classified wall refurbishment practices in three different groups, depending onthe position of the insulation as follows and will be referred as:Interior: when interior insulation is applied.Exterior: when exterior solutions like ETHIC, ventilated façade are applied.Cavity injection: when insulation is injected in the pre-existing wall cavity.Other practices:, there refurbishment practices have been classified under thisterm (i.e transparent insulation, and other new refurbishment practices)The main advantages or disadvantages, with reference to building energy consumption andIndoor Air Quality, have been identified for each of the practices:Table 1.:Exterior RefurbishmentExterior RefurbishmentFor load bearing wall.For hollow brick (exterior and interior) with cavityHollow brick (exterior and interior)with partly insulated cavity.

SUSREF5 (46)Only one sheet wallDouble reinforced concretelayers with insulationShort description:Heat losses are reduced or thermal transmittance is reduced by adding outdoorinsulation. Then a finishing layer is applied, whether acrylic, concrete mortar orceramic pieces in a ventilated façade.Apply waterproof mortar over existing to avoid moisture filtrations and thus, humidity.In a load bearing wall, an additional leaf of brickwork could be added to preventmoisture ingressThese options are suitable when external appearance change is not an issue..Advantages: There is no intrusion with the building tenants. Indoor spaces are not affected nor reduced. Thermal bridges are reduced, and therefore energy performance, is improved. Thermal inertia of the existing building elements is not changed. Indoor airtemperatures are smoother compared to solutions with indoor insulation. It prevents heat from sun irradiation on the outer walls to get into the dwelling.Summer indoor temperatures are smoother. Indoor air relative humidity doesn’t suffer major changes.Disadvantages: When aesthetics is an important issue, e.g cultural heritage, these techniquesare not applicable. Special attention should be paid when there is a limitation to the permittedincrease in external wall thickness in the exterior wall growth, In load bearing walls, strength test should be performed in order to know if wecan increase the load or we have to build another supporting layer. Window frames, balconies have to be studied in detail, otherwise thermalbridges would be enhanced and humidity problems may appear. Building air-tightness is increased and humidity problems may appear if thewall is not sufficient ventilated.Possible solutions or some issues to be considered: Particular Be care with joints: Avoidful, avoid the joints. Decrease the numberof joints by using with bigger pieces.Replace the finish layer for ceramic tiling with waterproof mortar or in a ventilated

SUSREF6 (46)façade.Note: Not all the solutions developed under SUSREF deliverable D4.1”development ofproduct concepts” have been illustrated. New refurbished layer, have been illustrated in redcolour.

SUSREF7 (46)Table 2.:Insulation injection in the existing air cavityInsulation injection in the existing air cavityPerforated face brick (exterior)with cavity and interior hollowbrickPerforated face brick (exterior)with cavity and interior hollowbrickShort description:When the existing wall has an air cavity, is possible to inject insulation –polyurethane,EPS-into the cavity by drilling through one of the existing walls.Advantages: Insulation is increased, and therefore, energy performance of buildings isimproved. Original aesthetic remains.Low intrusion technique. Building tenants don’t have to suffer refurbishmentworks.Disadvantages: Uneven distribution of insulation in the cavity, that could lead to thermalbridging problem. Increased air tightness. Air gap function is lost When the exterior layer is water permeable, insulation may get wet withinsome years, and internal condensations and mould problems may appear. Slab thermal bridges remain.Insulation thickness may not be enough to fulfil the new Building EnergyPerformance standards.Possible solutions or some issues to be considered:Avoid insulation injection in the cavity as far as possible. It would be better to insulateon outer or inner face of the wall because with the injection method the moistureproblem remains.

SUSREF8 (46)Table 3.:Interior refurbishment practices:Interior refurbishment practices:Load bearing wallSingle leaf. Only one sheet wallPerforated face brick (exterior)with cavity and interior hollowbrickShort description:Apply insulation layer and over this, put the plasterboard layer. The thickness of theinsulation can be modified to suit the European climatic zoneAdvantages: Exterior aesthetics of the building don’t change. For low occupancy buildings, it allows quick response for heating of the indoorair. When refurbishment at building level is not possible Window frame thermal bridges may be reduced if properly performed.Disadvantages:

SUSREF9 (46) Thermal inertia of the already existing building elements, except for slabs, willno longer be available. Higher indoor air relative humidity for low hygroscopic materials, especially insummer and southern European countries, that could lead to mould growth. Thermal bridges formed by slab and most of pillars remain. Future drilling of the insulation may lead to thermal bridges, cool points andmould growth. Air tightness of the dwelling is increased, adequate air renovations changeshave to be ensured. Intrusive technique. Tenants have to suffer refurbishment works. Indoor spaces are affected or reduced.As conclusion, there main watch-points are: In the buildings without waterproof outer materials there might be moisture and waterinfiltration problems Main problem: aesthetics. Always check the load resistance of the existing walls. Preferably choose:-Light or low load exterior coating.-Ventilated façade with self-supporting structure. Limited alternatives and solutions.. The contractor person requires:o Short term of execution.o Economic solutions.o Efficient solutions. Interior patios refurbishment is usually done the same way: insulate outdoor andmortar to finish. Beware of forming a sealed building: without adequate ventilation and correct vapourpermeability, refurbishment could create moisture problems where these did not existbefore. careful with the tightness of the building it could be self defeating to makehermetic dwellings. It can appear moistures that we haven’t first. While we do the refurbishment, we could incorporate renewable energy generationactive elements

SUSREF10 (46)3. Risks in building refurbishmentBuilding refurbishment may in general solve several kinds of existing problems. Improvedthermal performance of the envelope will generally contribute to indoor comfort, building partsdamaged or disfigured by dampness and mold may be removed or replaced, risk of internalcondensation may be removed or greatly reduced, and so on. However some risks are alsopresent. Risks related to indoor climate and moisture in construction are discussed below.3.1 Indoor climateHuman thermal comfort is determined by extrinsic factors like air and radiant temperatures,temperature asymmetry and gradients, relative humidity, air movement and clothing, as wellas intrinsic factors like activity, metabolic rate and individual characteristics and preferences.Comfort criteria has often been formulated on the basis of Ole Fanger’s comfort model asstated in ISO 7730. In recent years this model has been criticized for being too static, and e.g.not allowing for human adaptation to climate, see e.g. Moujalled & al 2008. This has led toadaptive models like the one incorporated in EN 15251, where a preference for higher indoortemperature in hot periods is presumed.A complete modelling of all the factors determining thermal comfort requires detailedinformation on building, furniture, technical equipment (HVAC-systems in particular) and use,as well as extensive CFD 1 -calculations. Since many of these factors vary between buildings,and are not to any great extent affected by wall refurbishment, assessment of indoor climaticeffects of refurbishment options is often restricted to effects on air and radiant temperaturesand relative humidity. These effects can be assessed by building simulation or in some casesby simply showing that the proposed refurbishment will improve the conditions in question.However, when refurbishment solutions interact with ventilation, heating and / or coolingsystems of the buildings, or moisture conditions are changed in an unfavourable direction,more detailed studies may be called for.3.1.1 Indoor temperatures - summerIn summer situations, the most common cause of discomfort is too high internal temperatures.If this is caused by high external temperatures, improving building insulation will reduce thisproblem. In cases where internal heat loads are high and outdoor temperatures are moderate,reduced heat flux though the envelope will increase indoor temperatures. The overall effectwill be longer periods with moderately high temperatures, but lower extremes. Since heat isonly removed from the building through the envelope when internal temperatures are higherthan external, the reduced heat loss could be compensated for by increasing the supply ofoutdoor air.Some refurbishment methods, most notable internal insulation, reduce thermal capacity of thebuilding. The effect of this is higher temperature fluctuation, most notably problematic as hightemperature peaks when external and / or internal heat loads are high. If a refurbishmentoption involves internal insulation of a structure with high thermal capacity, the overheatingissue should be given serious consideration. This implies that simulations of indoortemperatures should allow for uneven spatial and temporal distribution of heat loads.1 CFD:Computational Fluid DynamicsFormatted: Spanish (InternationalSort)Formatted: Spanish (InternationalSort)Formatted: Spanish (InternationalSort)Formatted: Spanish (InternationalSort)

SUSREF11 (46)Some refurbishment options aim at reducing the heating demand by utilizing solar radiation.Care should be taken that this does not lead to unwanted heating in hot periods by e.g.heating of intake air.3.1.2 Indoor temperatures - winterIn general, winter temperatures will be more comfortable after refurbishments aiming atreducing heating demand, as surface temperatures generally increases, and draughts arereduced. In cases where air infiltration through envelop is reduced, and ventilation relies onexhaust systems, local draughts from intentional or unintentional openings may be moreuncomfortable due to higher air speeds. Installation of heat exchange ventilation systemswould greatly reduce or eliminate this problem. .3.1.3 Indoor air relative humidity (RH)The indoor RH as such affects thermal comfort directly, but only to a very limited extent exceptin very hot and humid situations. It also affects perceived indoor air quality both directly andindirectly. Cool and dry air is generally perceived as favourable, while very low humidity maylead to rapid drying out of mucous membranes and tears film, and may thus be uncomfortable.Very low RH may also contribute to increased amount of airborne dust, while high RH mayincrease the amounts of mite and other allergens.The main determinants for indoor RH are the moisture content of intake air, internal vapourproduction, ventilation rate, indoor temperature, and dehumidification (including cooling withcondensation).Moisture diffusion through the building envelop might affect the internal RH, but for acceptableventilation rates and realistic constructions this effect is very small.The moisture buffering capacity of the building and interior may on the other hand have asubstantial moderating effect on diurnal and to some extent seasonal moisture fluctuations. Ifthe refurbishment involves introducing a vapour-tight layer on the inside of a wall with highmoisture storage capacity (e.g. aerated concrete) the effect on indoor RH may need to beconsidered.3.1.4 Internal condensation and microbial growth riskCondensation on internal surfaces occurs when the surface temperature is lower than thecondensation temperature – dew point – of the air adjacent to the surface. In cold climates,the process typically occurs near thermal bridges in the cold season. Refurbishment thatimproves thermal insulation usually alleviates this, but if thermal bridges are not improved,local problems around these may increase.Internal condensation may also occur in situations where hot, humid outdoor air meets coldconstructions of great thermal capacity. This is well known to cause seasonal problems incrawl spaces, garages and other constructions with little insulated below-ground walls. Wallrefurbishment would normally reduce the amount of such condensation, but in cases whereextra thermal mass is cooled by night ventilation and daytime supply air is very humid, diurnalcycles of condensation and evaporation may occur.3.1.5 Interstitial condensation riskCondensation may occur inside the building envelop when moisture is transported from a partof the construction with high vapour pressure to a cooler part of the construction. Thistransport may occur by diffusion or convection. Interstitial condensation most typically occurswhen the outside temperature is low, but can also happen when the outside air is much hotterthan the inside, and the outside humidity is high. The most familiar example of this is walls ofcold-storage chambers.

SUSREF12 (46)Whenever refurbishment involves added insulation, the temperature difference over theconstruction increases, and so the condensation risk also increases. It is important to assesswhether this change of conditions represents an actual risk of condensation. Risk of interstitialcondensation is much more dependent on the ratio of diffusion resistance between internaland external layers, construction air tightness and ventilation rates than the actual thermalinsulation. Thus, constructions with a good airtight vapour barrier retarder or vapour barrierand an external layer open to diffusion are considered robust against interstitial condensationeven up to very high insulation levels.3.1.6 External moisture loads and related problemsIn some massive and little insulated constructions the heat transport from the inside to theoutside adds considerably to the drying of the external surface. Internal insulation of thesewalls may lead to longer wet periods, and moisture-related problems like frost damage orexternal microbial growth may be aggravated.4. Assessment of refurbishment practicesThe correct design of refurbishment activities requires of properly addressing the preexistingsituation and the potential benefits of the proposed refurbishments. A wholistic approach isrequired, which needs of an exhaustive data gathering to allow a proper evaluation.In the following chapters, the needed data and the output of the evaluations are shown.4.1 Required dataThe base for the assessment of refurbishment practices is the constructive parameters of thebuilding, which includes several issues ranging from material properties to building geometryand glazing ratios. This information is then completed by available HVAC systems and userbehaviour.4.1.1 Building geometry: Geographic location of the building site: local climate, solar irradiation, outdoortemperatures, RH and rain will affect in the buildings dynamic energy andhygrothermal behaviour. Local weather files are required to consider building dynamicbehaviour. Building orientation: building or façades orientation may affect the incident radiation oneach of the walls of the building, affecting on solar gains, external walls superficialtempratures and construction drying process. Floorplan: one of the key parameters that will affect the energy performance of thebuilding is going to be the external surface/volumen ratio, this will affect thetransmission losses surface. The lower the rate, the less energy is requiered to keepindoor conditions. Height between slabs: height between slabs will affect basically the floor plan airvolumen ratio, and therefore, the air renovations, and the HVAC needs for airconditioning. It will affect at the same time, indoor RH, condtioned for exterior air RHand by moisture production rates. Window size and position. At least the glazing/façade ratio. Glazing area and theirorientation will affect solar gains through them. But at the same time, being windowsconstruction elements with weaker U values, these elements would lead to highertransmission losses Location and height of neighbouring buildings: neighbouring buildimgs affect on eachfaçades real available solar radiation, and therefore, on solar gains, superficialtempearatures and construction relative humidity.

SUSREF13 (46)4.1.2 Surface constructions Construction surfaces definition: Walls, roofs, slabs, internal partitions, basementslabs, glazing,.... for a proper energy and hygrothermal performance of building, it isnecessary to properly define each of the surface that compose the building.Dimensions, height, thickness, lay out. Shading elements, overhangs...etc that willaffect the presence of the shadows, solar radiation Composing materials of each surface construction: each construction surface may becomposed of one or more layers of materials. Depending on material properties i.e,thermal conductivity, thermal mass, water diffusivity, thickness… material sheets ofeach construction behaves differently, buffering or transmitting energy and moisture atdifferent speeds and thus buildings energy performance and indoors air RH may beaffected by the order layers are built on the constructions. Superficial claddings,vapour barriers and low emissive layers, though extremely thin, may affect a layersbehavior, especially in terms of solar radiation absorption, water diffusion and radiativeexchange. Therefore, proper definition of each layer, i.e. material, thickness, lay outand position is required in order to analyze the hydrothermal and dynamic energyperformance of a building.4.1.3 Material propertiesDensity, heat conductivity, thermal capacity, water diffusivity, emissivity… affect the way theenergy and moisture are buffered or transported across the building elements.Depending on the type of material opaque or transparent to solar radiation, the characteristicsor properties required to define them are different. At least the following will be requiredFor opaque materials (Walls, slabs,…) Thermal conductivity (k or ): is the property of a material to conduct heat (W/mK).Insulation materials have low values 0,026-0,040, concrete values are around 1-2W/mK. It is a moisture dependant value. The higher the moisture, the higher thethermal conductivity of a material. Moisture dependent values for widely usedconstruction materials are known and available in DIN1997. Thickness: layers thickness affect the construction’s total resistence and thermalinertia of the construction. Specific Heat (Usually not moisture-dependant)., is the capacity of a material to storethermal energy. The higher the value, the higher the energy required to increase itstemperature. Density: with specific heat it affects the capacity of a material to store energy. Porosity: most of building materials are porous and can be considered as beingcomprised of a solid matrix and pores filled with air. Moisture will be present in porousmaterials in different ways and affects moisture transport in materials. Relative humidity-Moisture content relatiionship curve: the moisture content of amaterial is indicated as the ratio of the weight of absorbed moisture to the dry weight ofthe material. Moisture content/Relative humidity dependant curves for:

SUSREF14 (46) Sorption curve gives the equilibrum relation between moiture content of the materialand relative humidity of air in contact with or entrapped within the material. Suction curve gives the equilibrum between moisture content of the material and liquidpressure of pore water in the material Water vapour diffusion resistance factor () ,represents the resistance to moisturetransport or movement through material pores in vapour state, compared to themoisture transpot in air. Mineral rocks are very permeable materials (1) whilematerials with low open porosity like vapour barriers have very haigh reisstnace factor500.000) Redistribution: liquid transport coefficient. Liquid transport in materials takes place bycapillary suction, Darcy flow and surface diffusion, being the Darcy’s law being thegoverning mechanism.For fenestration materials (Glazing) Solar heat gain factor: represents the total incoming solar energy compared to theincident energy on vertical wall. Thermal conductivity: Visible transmittance: represents the visible wave length energy that finally go throughthe window.For fenestration materials (Frames) Linear thermal transmitance Thickness of the frames4.1.4 Airtightness/Ventilation Air change rate of each conditioned or unconditioned space. If not constant, schedule.4.1.5 Occupancy Occupancy rate and schedule. Several occupancy rates should be required for mixedusebuildings. Moisture generation rate. Nominal power and use schedule of electric equipment, lighting devices, and otherheat sources.4.1.6 HVAC Present heating system, nominal power, efficiency rate Heating setpoint temperature and schedule (if not constant) Present cooling system, nominal power, coefficient of performance Cooling setpoint temperature and schedule (if not constant) Efficiency of heat recovery system, if present.

SUSREF15 (46) Definition of conditioned/unconditioned areas.4.2 OutputThe assessment procedure will provide information on the hygrothermal performance of thefaçade and the whole building. Depending on the performed approach, some of the data willnot be available.Building-level results will provide data on whole-building energy consumptions, Indoor airquality and partial data on the hygrothermal behaviour of façades. More in-depth façadeevaluations will provide a full characterization of the hygrothermal performance of façades.Building-level evaluations will provide the following data: Heating energy demand Cooling energy demand Ventilation energy losses Average insulation properties (RH) and thermal transmittance of façade constructions. Accumulated damage due to mould growth (EN ISO 13788:2001: RH above 80%), asa control variable for façade performance. Indoor Air quality (EN 15251:2007: RH above both 60% and 70% 2 and below both30% and 25%)The variables are split into three main categories: Temperature, water content and energyneeds. The variables that need to be obtained are listed. Depending on the case, some ofthem will not be necessary or complementary data should also be collected.Data collection should be collected at least in an hourly time series.Heat transfer rates through the envelope should be monitored in internal surface of thefaçades/roofs…Data provided by both Heat And Moisture Transfer methods and Conduction TransferFunction methods is similar, excepting that specific of moisture content.4.2.1 Temperature Exterior Ambient Temperature [ºC] Ambient Temperature of conditioned spaces [ºC] Temperature of unconditioned spaces [ºC] Surface temperature of external and internal walls, roofs or basement slabs [ºC]4.2.2 Water content Relative water content of the atmosphere [RH] Relative water content of conditioned spaces [RH] Relative water content of unconditioned spaces [RH] Surface relative water content of external and internal walls, roofs or basement slabs[RH] Relative water content of insulation materials [RH]2 UNE EN ISO 7730

SUSREF16 (46)4.2.3 Energy loadsNot only Heating/Cooling loads will be needed but also other heat flows will also be quantified: Heat transfer through walls, roofs, slabs and basement slabs [kW/m2] Sensible internal gains [kWh/m2] Latent internal gains [kWh/m2] Heat transport through ventilation [kWh/m2] Solar gains [kWh/m2] Heating/cooling loads [kWh/m2]4.3 Postprocess and data analysisTwo time bases will be used for data analysis. Whole year Monthly seriesA detailed analysis of the described phenomena should be made for each.Should heat recovery systems be present, the energy loads should be reduced accordingly,as stated in Deliverable 3.2.The relative humidity of insulation will be monitored and its thermal transmittance calculatedaccordingly as stated in deliverable 3.2.Interior air quality will be monitored as cumulative time in non-comfort ranges: interior air RH 70% interior air RH 60%Regarding mould growth, the cumulative time with wall internal surface RH>80 and surfaceT>0ºC (for Mould growth and corrosion).4.4 Other issues to be considered in simulationSome issues regarding hygrothermal simulation of buildings are not related to actual physicalproblems, but to numerical modelling, initialization and other issues in simulation processes.When addressing dynamic moisture transfer in buildings in software such as Energy+ ,numerical convergence can only be reached by short timesteps. These timesteps arerecommended to be shorter than 5 minutes.Also, as moisture transport is a slow process, the initialization of simulations is critical. This issomehow reflected in the need of simulating 4 years prior to the actual result-providingsimulation. These 4 years are used as an initialization process.

SUSREF17 (46)5. Phenomena to be consideredIn order to predict indoor environment and building energy consumption, important heat andmass flows must be described. Mass flows concern air as a whole, as well as some of itsspecific constituents, water vapour being one of them. For several applications, water vapourshould be treated separately. Indeed, it is the unique component of air that is able tocondense at usual conditions, resulting in the release of significant latent heat. The moisturebalance should therefore include both gaseous and liquid forms, e.g. by looking to vapoursources, transport by the air, diffusion and adsorption in solids. Water in its solid form (ice)may also appear in buildings, causing mechanical damages.It should also be stated that while working at a whole building level, we cannot go too deeplyinto the detail of each material and component. For example envelope parts are in generalporous media with a complex structure.The following Figure shows an example of a building with just some of the buildingcomponents, loads and transport processes that should be taken into account when analysingwhole-building hygrothermal processes. Most processes occur only locally, but may influencethe adjacent building elements such as rooms or structures. The physical conditions alsoinfluence each other, such as when the temperature determines the severity of moistureinfluences. To describe a whole building, it is necessary to set up heat, air and moisturebalances in various elements of the building, e.g. in individual rooms and constructions, or forfragments of these building elements. It also becomes important to study the interfaces, e.g. toknow how fluxes of heat, air and moisture into the building components depend on the localboundary conditions created by the micro climates of the rooms.Figure 3.: Building with indooe hygrothermal loads (Source: IEA. ECBCS. Annex 41)]

SUSREF18 (46)This point gives a general overview of physical phenomena, their interactions and the mainquestions relevant for building modelling.5.1 Energy fluxes.The energy performance of a building can be assessed by analaysing energy balances fromthermodynamics, taking into account the impact of thermal and mechanical energy. Theenergy conservation equation in a control volume can be written as the flow rate of thermaland mechanical energy that enters the volume minus the flow rate of thermal and mechanicalenergy that leaves the control volumen, plus the rate of energy generated in the volume, thatmust equal the rate of increase in the enerrgy stored in the control volumen.In most building applications, kinetic and potential energy contributions can be left out.Variation of energy of the control volume is then proportional to temperature variations,density and specific heat of the material composing the control volume.In buildings, pressure changes are very small compared to the total atmospheric pressure.Alternatively the rate of energy storage in the control volume can be assumed equal to internalenthalpy variations, proportional to specific heat at constant pressure for gases.In buildings, the rates of energy entering or leaving the system are heat fluxes and energyfluxes due to mass flows. Basically heat transfer modes can be distinguished that generateheat fluxes; they are all due to a temperature gradient:Enthalpy flows: as some control volumes in buildings are open systems, there is amass flow transporting energy into and out of the system. Mass flow is typically airand/or water in vapour or liquid state. Room volume with air flowing in and out is aperfect illustration. The mechanical work associated with a mass flow is due topressure forces moving the fluid through system boundaries.Convective heat flow: Convective heat flow refers to heat transfer between a solidsurface and a surrounding fluid, or within fluids. The convective heat transferprocesses for air are relevant in building applications as concerns conditions in theoutdoor environment, heat flow in rooms, as well as heat flow in cavities in buildingelements or even in pores in building materials.The convective heat transfer coefficient between a solid surface and a fluid hastraditionally been determined empirically, based on some characteristic situations, orcalculated using detailed modelling of non-isothermal fluid flow. It is highly dependenton air flow conditions whether caused by forced convection or natural convection. Innatural convection the driving force is buoyancy induced by variations of air density ina volume.For building applications it is common to consider that indoor heat transfer is mainlydue to natural convection and therefore is temperature dependent, and outdoors theheat transfer is mainly due to forced convection and therefore is wind velocitydependent.In many practical applications, the convective heat transfer coefficient is directly givenas a constant value. For outdoor convection, the dependency on wind speed is morestraightforward because outdoor air velocity is in general given in the weather file. Thepossible difficulty lies in the estimation of local wind velocities close to the buildingsurfaces.Radiative heat flow: Thermal radiation heat flow involves the exchange ofelectromagnetic waves between surfaces. In building applications, two wave-lengthsare of importance:So-called short-wave radiation, mostly concentrated in the visible spectrum, comingfrom very hot sources. In normal buildings this terms refers exclusively to solarradiation and light.

SUSREF19 (46)So-called long-wave radiation, mostly concentrated in infrared spectra, coming from allsurfaces at ambient temperature.Solar radiation is mainly short-wave and is composed of direct and diffuse radiation.Outdoor solar radiation is given in weather files as boundary conditions. Then takinginto account building geometry, solar shadings and relative position of sun, solarirradiation on each building surface can be computed. Solar transmission throughwindows can also be assessed, using transmittance properties of windows.Infrared radiation exchange is relevant for both indoor and outdoor surfaces. Radiativefluxes are proportional to the absolute temperatures raised to the fourth power, andtherefore introduce non-linear terms in the heat balance equations.Indoor exchanges take place between indoor building surfaces, and outdoorexchanges between outdoor building surfaces and the surroundings. In general,ground and surroundings are assumed to be at the outdoor air temperature.Heat flow in materials and structures (conduction): Heat transfer in solids isdominated by conduction, which is energy transport by molecular activity without anybulk motion. For some simple cases analytical solutions can be found. For morecomplex cases numerical computations using diverse techniques (such as finitedifferences, control volumes, response factors of finite elements) are helpful. The maindifficulty for building problems comes from the coupling of the generalized heatconduction equation with mass transfer in porous mediaTo describe a whole building, it is necessary to set up heat, air and moisture balances invarious elements of the building –rooms and constructions, or for fragments of those buildingelements. But it also becomes important to study the interfaces, e.g. to know how heat fluxes,air and moisture affect in certain points or construction elements where boundary conditionsare different – i.e cracks, thermal bridges, massive construction elements...- from actualbuilding conditions, and may lead to local problems of condensations, cooler temperatures...Issues to be considered, Thermal bridges: A thermal bridge is created when materials that are poor thermalinsulators come into contact, allowing heat to flow through the layer. This is usually theweakest point of an envelope and special care is required to prevent heating escapingfrom the building. Cracks: This is one of the most common problems that can be found in buildingenvelopes. The most general cause of cracking is structural movement of the buildingwith a rigid covering, which is not able to absorb that movement. Rain water enters thecracks, and when it freezes, its volume increases, making the crack bigger andconsequently the problem gets worse. Massive construction elements. These are elements of high thermal inertia, whichmeans that they work as a storage system and controls the time delay of the heattransfer from outside to inside. In winter insulation is required to avoid losing thebuilding heat. On the other hand, in summer a solar protection or something that coolthe element is needed to protect the walls from excessive radiation.5.2 Air balancesVentilation plays an essential role as it maintains good indoor air quality by diluting andremoving pollutants, such as human bio effluents, humidity released by occupants and theiractivities and pollutants from material and furnishings. Sometimes ventilation also helps inmeeting cooling needs. A low-energy ventilation system should reconcile two oppositerequirements: an adequate air flow for satisfactory indoor air quality and a minimal air flow toreduce energy consumption.A general expression of mass balance applied to a control volume can be written as:

SUSREF20 (46)Where:dmdtair m air : is the mass of air [kg] air, in is the density of air [kg/m3].V is the volumetric flow [m3/s]air, inVin air,outVoutAir flows in buildings involve significant transfer of energy and moisture. The airflows are dueto pressure differences driven by wind pressures, buoyancy forces, or some mechanicaldevices, such as fans. Buoyancy forces depend on the variations of air density, which istemperature and moisture content dependent.Air flow in rooms are due to combined effect of buoyancy forces in non-isothermal conditions(natural convection) and additional pressure differences induced by wind, fans, or stack effect.But, at the whole building level the usual approach is to assume a perfectly mixed air zone.The ventilation may be achieved by natural ventilation – through large openings in theenvelope- or through ventilated systems like HVAC. Mechanical systems: HVAC Air filtration through building envelopes Air flow through large openings open doors, window…Mechanical systems:Mechanichal systems are devices where ventilation is provided by mechanically poweredequipment, such as motor-driven fans and blowers, but not by devices such as wind-driventurbine ventilators or mechanically operated windows.Mechanical systems alllow the possibilty of using energy recovery ventilation systems thatpreheat the incoming outdoor air for ventilation transferring heat from the exhaust heated airto the intake airThese mechanical systems force the air flow inside the building, mainly by injection jets thatcreate air streams. The term ’forced’ is used as the flow is not driven by the temperature ordensity fields.Therefore, inside buildings both forced and natural convection will occur. Sometimes they willoperate even at the same place and time, what is called mixed convection. Depending on theair flow driving forces, convection coefficients may be affected, and thus,heat energy transfercoefficients..Air filtration through building envelopes through cracks or large openings:Inter-zonal air flows are in fact flows through the building envelope and interior partitions dueto pressure differences across openings. The openings may be deliberate such as vents orducts, or unintended such as cracks due to construction imperfections. In some particularcases where materials are very air permeable, the air may flow through the entire wall.Therefore, three types of openings can be distinguished: small openings, large openings, andpossible air flow through porous materials on the walls.The driving force for that air movement is the pressure difference that can be intentionallyimposed using fans (described above) or may occur due to wind pressure or buoyancy effects.

SUSREF21 (46)Air flows through the envelope may have a significant impact on the local hygrothermalconditions within the envelope, especially in cracks, that may lead to local condensation andmould growth. Indeed local phenomena in the air path impact on local temperature andhumidity distribution in the neighbourhood of the opening. Condensation and mould growthoccur locally and depend on local temperatures but also on local air flows. Therefore very –finely or finely granulated models like CFD3 in air or 3D fine mesh in envelopes or 2 Denvelopes are required to analyse these particular problems .(Annex 41 ECBCS).5.3 Moisture balancesThe equation for conservation of mass (m, kg) of water within a volumen element can bewritten as:dmmoisture Gvapourdiffusion GliquidGconvection Gvapour diffusion GliquidGdt ininin outoutoutm moisture =m liquid water +m water vapourconvection msourceWherem is the mass of moisture and is referred to the sum of liquid water –condensedor adsorbed phase- and the vapour form.G is the moisture flow through the surfaces of the control volume.m is a volumetric moisture production rate.For moisture in porous materials, the mass of water vapour in the pores is most likely to benegigible compared to the mass in the adsorbed or condensed phases. The opposite is thecase for cavities in constructions, where the mass of vapour will be greater than the mass ofcondensed moisture. Nevertheless the mass of humidity in the air of a room is rather smallcompared to the mass of moisture that is stored in building and building’s construction.Moisture in the air: water in the air is mainly present in vapour state, though on someoccassions, it may occur in small droplets for example after a hot shower. Te moisture contentof air can be indicated by the humidity ratio (mass of water per mass of dry air), partial waterpressure, humidity by volume or by dew points.5.3.1 Moisture in materials:Most building materials are porous and can be considered as being comprised of a solidmatrix and pores filled with air. Moisture will be present in porous materials as water vapour inthe air-filled pores, as adsorber layers of eater molecules on the internal pore wall surface, ascapillary condensed liquid water in the fine pores, as bulk water in the coarse pores, and aswater which may be physio- chemically bound in the material that constitutes the solid matrix.The moisture content of a material is indicated as the ratio of the weight of absorbed moistureto the dry weight of the material.A certain pressure of water vapour will exist in the pore air depending on the moisture contentof the material. The liquid moisture that may exist in the capillaries of the material will exert acertain liquid pressure depending on how much moisture is absorbed in the material. Ingeneral, equilibria exist betweeen these pressures and moisture content, and the equilibriaare described by the two types of retetention curves:3 CFD computacional Guild dynamic.

SUSREF22 (46) Sorption curve that gives the equilibrum relation between moisture content of thematerial and relative humidity of air in contact with or entrapped within the material. Suction curve that gives the equilibrum between moisture content of the material andliquid pressure of pore water in the material5.3.2 Moisture transport in materialsMoisture transport is in general caused by the following processes: Vapour: diffussion Liquid: capillary suction, Darcy Flow and surface diffussion. Convective moisture flow.5.3.2.1 Water vapour diffusionVapour diffusion is a moisture transport mechanism that takes place conditioned by aconcentration or partial pressure gradient, and it is governed by Ficks law. It is a relativelyslow mechanism compared to other transport forms. However, when liquid and convectivemoisture transport do not take place, vapour diffusion becomes the governing form of moisturetransport and should certainly be considered. This would be the case for air tight materials inthe hygrocospoic regime and would be the most common transport form for materials incontact with indoor air.5.3.2.2 Liquid moisture transportLiquid transport redistribution coefficient. Liquid transport in materials takes place by capillarysuction, Darcy flow and surface diffusion, the Darcy law being the governing mechanism,suction being the driving force for this movement. The water permeability is a function ofmoisture content. As more pores and larger pores are filled with water, the liquid moisturetransport will be significantly enhanced.Figure 4.: Moisture permeability in a porous media. Water vapour difussion and liquid moisturetransport (Source: Transferencia de humedad en cerramientos. Iñaki Gomez Arriarán)

SUSREF23 (46)5.3.2.3 Convective moisture transportAdvective moisture transport or convective moisture transport occurs when a flow of humid airpasses through a porous material or through craks and joints in an assembly. When present,convective moisture should be minimized by preventing undesired air leaks in construction.However convective moisture flow may also, under some weather conditions, be a significantway to dry out excess moisture from constructions, such as by outdoor ventilated cavities andventilated attics.5.3.3 Moisture sources and moisture production rate.There are four aspects that limit humidty levels in builidings Human health and comfort: human beings react to global environmental conditions,and comfort conditions can be achieved by different combinations of variables, beingRH one of the variables that affect human thermal comfort. Present thermal comfortstandards allow RH to vary considerably (ISO 7730), but should meet 30-70% limits toavoid dry skin, eye irritation, respiratory problems, microbial growth, and othermoisture related phenomena. Deterioration of furnishing, high or extremely low RH levels may change size andshape, induce chemical reaction and favour bio-deterioration of furnishing, so that isimportant to keep indoor air RH at certain levels. Safeguarding the building fabric: building fabric may be affected by mould growth,wood deterioration and corrosion on metal surfaces. The growth of algae on façades isconditioned by the availability of sufficient water. The formation of dew at night whentemperatures fall below the dewpoint is of special importance, as is the mechanismexplaining algae growth on north facing façades. Minimizing final energy consumption, energy efficiency may conflict with coping withmoisture tolerance, in the sense that avoiding moisture-related problems like mouldcould require extra energy. The task is to identify how to combine effective moisturemanagement with using less energy.Therefore, the knowledge of indoor air humidity and temperature of buildings is important toavoid all these problems. The main sources of moisture that may affect indoor air are exteriorweather conditions, moisture that is generated by occupants and their activities and moisturereleased by building components or construction material the period after construction.5.3.4 External sources that might affect interior indoor conditions:Many sources of excess moisture can lead to high indoor humidity and cause a wide range ofproblems. The main sources of moisture to the indoor air are: The moisture release from the building envelope components to the indoor air: Thisis more important during the initial years of the construction when the constructioncomponents release their initial moisture contents during their first drying process. Moisture that is related to the exterior weather condition: In humid climate asignificant amount of moisture can be carried into the indoor environment by means ofair leakage through cracks and unintentional openings, or by an intended natural ormechanical ventilation system.Wind-driven rain: this phenomenon is rain that is given a horizontal velocitycomponent by the wind. It is one of the most important moisture sources affectingbuilding facades because it penetrates the building envelope enclosure throughdefects and deposit liquid water inside the construction.

SUSREF24 (46) Moisture migration from wet soil through walls and floor slabs by capillary force: thisis a major source of moisture to the indoor environment and can cause numerousproblems, such as mould and mildew growth, damp, wet insulation, musty smell andbacteria growth. To reduce this sort of problem, the flow of moisture from outside hasto be stopped and al leaks must be fixed.5.3.5 Internal sources of moisture:Some indoor moisture production always occurs and can be considered as normal, butwhenever possible, sources of excess indoor moisture should be removed or ventilated.Occupants: Most moisture produced inside a building is the result of people´srespiration and perspiration. The released amount depends on their activities. Whenthere are many occupants in a reduced space, moisture could be a problem.Domestic activities: Baths and showers, cooking, dish washing and laundry increasethe quantity of moisture production.Crawl spaces represent one source of moisture in buildings, so that is important tocover the ground with a vapour barrier. If this is not done high humidity can build up inthe crawl space, contributing to increase humidity inside a building.Air conditioners: Air conditioners cool the air, and raise the relative humidity.Occasionally, an air conditioner which is not well design for the space it is cooling canmake the problem worse. An air conditioner of the proper size should be used to avoidthis problem.Plumbing leaks: Sometimes, moisture problems are the result of plumbing leaks.They may be hidden in building cavities such as walls or underneath toilets.The inadequate use of exhaust fans and the poor ventilation of high-moisture areas, such askitchens and baths, cause damage in those areas. If kitchen and bath fans are not installed ornot used, moisture problems commonly arise soon. Adequate ventilation should correct thesemoisture problems.6. Assessment toolsThere are different tools or ways to address buildings energy performance, indoor air qualityconditions and construction quality. Depending on the required detail level of the data, tools atbuilding level could be enough but with issues related, for example, with cold bridges, zonesexposed to high humidity, poorly ventilated areas, corners...- special attention should be paid,and will require more detailed studies that take in account the special boundary conditions thatoccur near these points.This point has been considered at two agregation levels, at building level and at constructionlevel.6.1 At building levelThe methods to calculate energy performance or indoor air quality at building level can beclassified as steady state methods or dynamic methods.

SUSREF25 (46) Quasi-steady-state methods are those that calculate the heat balance over asufficiently long time (typically one month or a whole season) using daily or monthlymean average temperatures, and which enable to take dynamic effects into account byan empirically determined gain and/or loss utilization factor. Most building internationalstandards fall under this category. Dynamic methods, are those that calculate the heat balance with short times steps(typically one hour) taking into account the heat stored in and released from the massof the building.6.1.1 StandardsStandards related to energy performance set the basis or the methodology to characterize thethermal performance of building and define the required boundary conditions.The main standards that develop thermal energy performances methodologies are the EN 832- Calculation of energy use for heating-residential buildings and ISO 13790: Energyperformance of buildings- calculation of energy use for space heating and cooling.Both of them develop quasy steady state methods for heating and cooling energyconsumption estimation.6.1.1.1 EN 832: Thermal performance of buildings- Calculation of energy use forheating- residential buildings.This standard provides a simplified calculation method for assessment of heat use and energyneeded for space heating of a residential building. It is not developed a specific method forcooling, and doesn’t consider air quality.We would recommend this tool when a rough idea of the whole building heating energydemand before and after the refurbishment is needed.But monthly heating demands predicted by this tool may differ substantially from actualdemands, especially in the beginning and end of season: It is not a tool for systemdimensioning. And no issues related to indoor air relative humidity are addressed.This standard is based on steady state energy balance, but takes into account monthly orseasonal external temperature variation, indoor temperature set point, the dynamic effect ofsolar and internal gains, and transmission and ventilation losses. It is based on energytransfer, but neither moisture transfer nor latent heat is considered.The standard only applies to residential buildings.The building heating demand is a relationship between heat losses –transmission andventilation- and heat gains – internal and solar- and a reduction factor for the heat gain, toallow for the dynamic behaviour of the building.The calculation method relies in the following equations:WhereQ h = Q loss - Q gainsQ h is the building energy need for continuous heating,Q loss is the total heat transfer losses (transmission and ventilation)Q gains accounts for heat gain (internal and solar). H,gn is the dimensionless gain utilization factor.

SUSREF26 (46)Where heat loss at constant internal temperature it is calculated by the following equation: (H Hv) ( i e) tQ lossT i = is the internal set-point temperature e = is the average external temperature during the calculation period:t: is the length of the calculation periodH T : is the heat loss transmission coefficient, through the envelope elements,calculated by the relationWhere:H T = AiUi lkk A i is the area of element i of the building envelope, (m 2 )U i is the thermal transmittance of element i of the buildingenvelope, expressed in (W/Km 2 );l k is the length of linear thermal bridge k, (m) k is the linear thermal transmittance of thermal bridge k,expressed in (W/Km)j : is the point thermal transmittance of point thermal bridge j,H V : is the ventilation loss coefficient. That is calculated byH v = V aCa,where:V is the air flow rate through the builiding; related with air changerate (n) and conditioned space volume (V) , V= nV aC ais the heat capacity of the air per volume. 0,34 Wh/m 3 KxjWhere heat gains, are calculated, summing up the internal gains (Q g ) and solar gains (Q S ).Q g= Q i + Q sInternal gains (Q i ) result form the metabolic gains from occupants, power consumptions ofappliances and lighting devices…)And solar gains resulting from the local sunshine irradiation (I) and the solar transmission (SHGC of glasses, transparent covering, transparent insulation….) and absorptioncharacteristics of the collecting areas – i.e., walls behind a transparent covering-..Solar irradiation is available from meteorological data, and transmission and absorption areproperties inherent to materials.Internal gains can be calculated from the power of appliances and internal loads.6.1.1.2 ISO 13790: Energy performance of buildings- calculation of energy use forspace heating and coolingCompared to Standard EN 832, ISO 13790 applies to residential and tertiary buildings.

SUSREF27 (46)Like EN 832, this standard deploys steady state energy balance algorithms to estimate spaceheating demands for buildings, and it uses a mirror image of the approach for heating forcooling loads.As with EN 832, the monthly calculation gives correct results on an annual basis, but theresults for individual months close to the beginning and the end of the heating and coolingseason can have large relative errors.In addtion, ISO 13790 allows more detailed specifications than EN 832, allowing tointroduction of schedules with different set point, ventilation rates, internal heat gains,moisture generationAn alternative simple method for hourly calculations has been added to facilitate thecalculation using hourly user schedules (such as temperature set-points, ventilation modes,operation schedule of movable solar shading and/or hourly control options based on outdooror indoor climatic conditions). This method produces hourly results, but the results forindividual hours are not validated and individual hourly values can have large relative errors.6.1.2 Dynamic simulation tools and methodsDynamic thermo-energetic methods are based on temporal evolution of different points of thebuilding due to dynamic excitations (i.e weather and building use related). The complexity ofsolving temporal/spatial equations, has led to the development of several simulation softwareprogrammes (i.e EnergyPlus, TRNSYS, IDA-ICE….)But compared to quasi-steady state methods, results are generally more precise, allow dataanalysis for shorter period of times, i.e monthly, weekly, daily or on hourly basis and allow theestimation of peak power demand in order to dimension an HVAC system.Nevertheless, though it seems that the more complex the model is, the better results will be,this is not so simple. Some results from very complex calculations, which require very preciseand numerous input data, and hours or days of project definition and simulations, canseriously miss the experimental evidence. At the same time, a simplified model programmedin a spreadsheet can give a realistic estimate of the overall behaviour. Therefore, specialattention should be paid to defining boundary conditions and the building itself. (for furtherdetail, please refer to ISO 13790)Some of the well known building energy simulation software, like EnergyPlus and TRNSYSare able to simulate the energy flows in a building in dynamic conditions, and are mainlysituated at the intermediate level of “granularity”. All the models also calculate the moisturelevel in the indoor air and can account for moisture storage in hygroscopic material. Thoughwater vapour exchange between room air and surrounding material (walls and furniture) isgoverned by three physical processes (transfer of water vapour between the air and thematerial surface, the moisture transfer within the material and the moisture storage within thematerial), not all the phenomena are always considered in simulation tools.Nowadays different numerical models are available to describe the transient water vapourbalance of a room and predict indoor air humidity. A typical room moisture balance includeswater vapour production by moisture sources (humans, plants… ) convective water vapourtransfer with infiltration and ventilation air, and water vapour exchange with the building fabricand furniture.6.1.2.1 Energy plus with HAMT and CTF. Energy demand differences

SUSREF28 (46)EnergyPlus is a very strong whole building energy model that accounts for energy andmoisture, (moisture sorption by building materials) and ventilation which allows naturalventilation and mechanical system to interact more fully.Depending on the required data output, i.e energy consumption or energy consumption,indoor air RH, and envelope’s material water content, two main different algorithm may beused:CTF: Conduction Transfer Function –CTF- Conduction transfer functions are anefficient method to compute building energy demand. The zone heat gains consist ofspecified internal heat gains, air exchange between zones, air exchange with theoutside environment, and convective heat transfer from the zone surfaces. However,conduction transfer function series become progressively more unstable. (EnergyPlusEngineering reference).HAMT: The combined heat and moisture transfer finite (HAMT) solution algorithm is acompletely coupled, one-dimensional, finite element, heat and moisture transfermodel simulating the movement and storage of heat and moisture in surfacessimultaneously from and to both the internal and external environments. It alsosimulates the effects of moisture buffering,HAMT is also be able to provide temperature and moisture profiles through compositebuilding walls, and help to identify surfaces with high surface humidity.As mentioned before, the level of the input data required and the computational time areincreased considerably from CTF to the HAMT. Because the diffusion of the water onconstruction materials is a slow process, it requires more than 5 year simulation period beforeresults stabilize, which lead to higher computational times. Once the system is stabilized, ithas been observed that both heating and cooling demands calculated with HAMT are lowerthan those calculated with CTF. In HAMT calculations the façade water content mass is takeninto account, consequently walls have more thermal inertia and worse conductivity, but in anycase, it is expected that thermal inertia prevails, which reduces the calculated energyconsumption (for further detail, please refer to SUSREFdeliverable D3.2 ” Energy and ThermalBehaviour of building types”.)6.1.2.2 IDA-ICEIDA Indoor Climate and Energy (IDA ICE) is another dynamic tool for the simulation of energyconsumption, indoor air quality and thermal comfort.IDA ICE covers a large range of phenomena, such as integrated airflow networks and thermalmodels, CO 2 and moisture calculation, vertical temperature gradients and day lightpredictions. To calculate moisture transfer in IDA-ICE, the common wall model RCWall shouldbe replaced with HAMWALL. Vapour diffusion through the envelope is considered in moisturetransfer is modeled. The liquid water transport is not modeled and hysteresis is not taken intoaccount. Many different cases in whole building, heat and moisture transport can be simulatedwith IDA-ICE, however for comprehensive moisture simulations the computational time israther high compared to only energy simulations and the interface is not very “user friendly”.(IEA, Annex 41)This points shows the different results for a case study simulated EnergyPlus and IDA-ICE.6.1.2.3 Benchmarking of several dynamic simulation tools for selected casesA benchmarking process has been carried out to assess the differencies obtained when usingdifferent modelling tools such as Energy Plus and IDA ICE for three façade refurbishmentalternatives. These two software have been applied to case studies in two countries and theirability to handle identical cases assessed.

SUSREF29 (46)Simulations have been performed for refurbishment alternatives and regular local buildingtypes of Spain and Norway presented in deliverable 3.2. Buildings for Spanish and Norwegiancases are similar, but not the same, therefore they have been named as Building 1 andBuilding 2.A total of 6 cases were simulated with both software, Energy Plus and IDA ICE.Energy Plus, Building 1, Barcelona weather, Solid brick wall, F1.Energy Plus, Building 1, Barcelona weather, Brick cavity wall, F2.Energy Plus, Building 2, Oslo weather, Insulated wood frame.IDA ICE, Building 1, Barcelona weather, Solid brick wall, F1.IDA ICE, Building 1, Barcelona weather, Brick cavity wall, F2.IDA ICE, Building 2, Oslo weather, Insulated wood frame.Additionally, an orientation-dependent study was made to all of the cases, ny rotating thebuilding 90°.6.1.2.4 Initial data6.1.2.4.1 Building systems and geometryThe initial data was defined mainly according to deliverable 3.2. Some differences were foundfrom both Norwegian and Spanish cases and the data not according to the D3.2 isrepresented in table 5,Table 4.:. Building geometry, initial data.SpainNorwayWindow area, south 26 % (16,2m²) 35 % (8,4 m²)Window area, westWindow area, north 24 % (15 m²)26 % (16,2 m²) 35 % (8,4 m²)20 % (2,4 m²)Window area, east 24 % (15 m²) 10 % (4,8 m²)The structures were defined according to the deliverable 3.2 and structural attributes used inIDA ICE simulations are as close to the values used in Energy Plus simulations as possible.U-values of the constructions used in IDA ICE are presented in the following table. EnergyPlus does not provide the U-values of the constructions, therefore they are not known.Table 5.:Structures used in IDA ICE simulationsStructure type Materials U-valueW/m²KExt. wall, Structure F1Ext. wall, Structure F2Solid brick façade, noinsulationBrick cavity wall, noinsulation0,920,91Ext. wall, Structure 3 Insulated wood frame 0,42Ext. RoofSpain: WoodNorway: wood with0,090,32Other

SUSREF30 (46)insulationExt. Floor Spain: ConcreteNorway: Concrete withinsulation2,30,64Int. Wall Gypsum 1,7Window 1 layer2 layersSpain 5,8Norway 2,8SHGC 0,59Table 6.:SystemsSystem Spain NorwayVentilation Natural ventilation 0.5 ACH (summer4 ACH)0.35 ACH (summer1.85 ACH)Infiltration Natural ventilation 0 0.15 ACHHeatingCoolingIdeal heaterno coolingTable 7.:Internal loads, Spanish casesLoad type Schedule, weekdays Schedule, weekendsOccupancy 3,86 people /building(~2 people /zone)0-8 (100 %), 8-16(25%), 16-24 (50 %)Lighting 4,4 W/m² 0-8 (10 %), 8-18 (30%),18-19 (50%), 19-23(50%), 23-24 (100 %)Equipment 4,4 W/m² 0-8 (10 %), 8-18 (30%),18-19 (50%), 19-23(50%), 23-24 (100 %)24 h (100 %)0-8 (10 %), 8-18 (30%),18-19 (50%), 19-23(50%), 23-24 (100 %)0-8 (10 %), 8-18 (30%),18-19 (50%), 19-23(50%), 23-24 (100 %)Table 8.:Table 1. Internal loads, Norwegian caseLoad type Schedule, weekdays Schedule, weekendsOccupancy 0.033 people / m² 24 h (100%) 24 h (100 %)Lighting 2.9 W/m² 0-7 (0 %), 7-24 (100%) 24 h (100 %)Equipment 4 W/m² 0-7 (0 %), 7-24 (100%) 24 h (100 %)6.1.2.4.2 WeatherWeather files used in IDA ICE and Energy Plus simulations were compared to ensure theywere similar. They were nearly identical.The following figure represents the outdoor air temperature of the weather data used.

SUSREF31 (46)Simulation weather data30,025,020,015,0Tout, °C10,05,00,0-5,0-10,01 2 3 3 4 5 6 6 7 8 8 9 10 11 11 12 12-15,0-20,0Time, monthsBarceonaOsloFigure 5.:Weather data used in simulations6.1.2.5 Results6.1.2.5.1 Presenting of resultsEnergy Plus and IDA ICE have different categories of presenting the results.Energy Plus: Heat flux to the building throughenvelope Heat flux from the building throughenvelope Sensible internal gains Latent internal gains Heat losses through infiltration Heat gains through infiltration Heat losses through ventilation Heat gains through ventilation Solar gains Heating loadsIDA ICE: Envelope and thermal bridges Internal walls and masses External window and solar Infiltration and openings Occupants Equipment Lighting Local heating unitsIn IDA ICE the gains and losses of different factors are not presented. The result is the energyconsumption where several different factors of each category of energy consumption havealready been taken into consideration. The result is not purely heat flux in or out, but e.g.yearly total of heat flux in and out through window during the year.

SUSREF32 (46)In Energy Plus results are presented separately as gains and losses, and it is uncertain whatthe different factors of heating energy consumption consist of. It seems that they describecertain of the heat flows in or out of the through the building envelope, and not the yearly totalthat would include both, heat flux in and out.In IDA ICE heat losses through envelope and windows have been separated, and in EnergyPlus there is heat flux to the building through envelope and heat flux from the building throughenvelope. Th “Solar gains” are shown separately, and are much bigger that heat gainsthrough the envelope. This suggests that the windows are not included in the envelope area.What is contradictory is that the “Solar gains” is only a positive value, and it suggests thatthere are no heat losses through windows, or that they are very small in comparison to thegains. This result is similar in all the cases, including the Norwegian case, which suggests thatthere is something more behind these values than stated here.6.1.2.5.2 Spanish casesThe energy simulation results performed with Energy Plus are represented in the followingtables, as they are presented by the simulation software used in the case simulation. The lastrow “Heating loads” or “Local heating units” represents the total heating demand for thespaces, and they include effects of all the loads, losses and gains.Table 9.:Table 2. Results, Spain, F1, Energy PlusTotal 1 2 3 4 5 6 7 8 9 10 11 12kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWhHeat flux TO the buildingthrough the envelopeHeat flux FROM the buildingthrough the envelope4649 48 81 101 153 195 783 762 993 935 379 158 62-20496 -3560 -3130 -3288 -2587 -1567 -454 -398 -344 -334 -554 -1444 -2835Sensible internal gains 6580 559 505 558 543 558 540 560 558 541 559 540 560Latent internal gains 1189 101 91 99 100 99 97 103 99 98 101 97 103Heat losses through ventilation 10256 1072 956 933 733 537 860 812 972 1042 569 727 1045Heat gains through ventilation 119 0 0 0 0 2 33 37 31 14 3 0 0Solar gains 19786 963 1286 1630 1710 1971 2074 2221 2195 2020 1724 1085 908Heating loads 15413 3167 2651 2712 1984 1009 4 0 0 0 134 1191 2562Table 10.: Table 3. Results, Spain, F2, Energy PlusMonth Total 1 2 3 4 5 6 7 8 9 10 11 12kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWhHeat flux TO the buildingthrough the envelopeHeat flux FROM the buildingthrough the envelope4723 46 80 101 152 201 802 794 1008 945 380 153 60-20651 -3603 -3152 -3292 -2590 -1552 -460 -401 -346 -335 -562 -1474 -2884Sensible internal gains 6580 559 505 558 543 558 540 560 558 541 559 540 560Latent internal gains 1189 101 91 99 100 99 97 103 99 98 101 97 103Heat losses through ventilation 10205 1069 954 930 729 532 859 817 966 1034 556 719 1041Heat gains through ventilation 123 0 0 0 0 2 34 38 32 15 3 0 0Solar gains 19786 963 1286 1630 1710 1971 2074 2221 2195 2020 1724 1085 908Heating loads 15522 3199 2667 2716 1987 995 3 0 0 0 139 1217 2599

SUSREF33 (46)Table 11.: Results, Spain, F1, IDA ICEMonth Total 1 2 3 4 5 6 7 8 9 10 11 12kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWhEnvelope & Thermal bridges -10014 -1508 -1198 -1074 -857 -780 210 -413 -640 -552 -456 -839 -1297Internal Walls and Masses -146 -9 -17 -19 -28 -51 -34 -23 1 11 24 -2 -13External Window & Solar 2295 -1244 -600 -152 409 860 773 1445 854 621 373 -501 -992Infiltration & Openings -12423 -1474 -1189 -1112 -886 -699 -605 -1541 -706 -598 -671 -937 -1251Occupants 1976 206 181 194 186 169 122 124 85 124 171 190 202Equipment 2293 195 176 195 188 195 188 195 195 189 195 188 195Lighting 2548 216 196 216 209 217 209 217 217 210 216 209 216Local heating units 13512 3617 2453 1757 786 96 0 1 0 0 151 1694 2938Table 12.: Results, Spain, F2, IDA ICEMonth Total 1 2 3 4 5 6 7 8 9 10 11 12kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWhEnvelope & Thermal bridges -10051 -1508 -1198 -1077 -855 -778 210 -416 -647 -559 -468 -849 -1297Internal Walls and Masses -148 -9 -18 -20 -29 -51 -34 -23 1 11 23 -1 -13External Window & Solar 2313 -1240 -601 -152 409 859 773 1448 858 627 381 -503 -993Infiltration & Openings -12417 -1474 -1190 -1111 -886 -701 -605 -1539 -703 -596 -669 -937 -1251Occupants 1976 206 181 194 186 169 122 124 85 124 172 190 202Equipment 2293 195 176 194 188 195 188 195 195 189 195 188 195Lighting 2548 216 196 216 209 217 209 217 217 209 216 209 216Local heating units 13528 3613 2454 1760 785 96 0 1 0 0 154 1705 2939The following figure presents the yearly variation in the heating energy demand in Spanishsimulation cases with both Energy Plus and IDA ICE cases.Spain, Heating energy consumption, consturction F1 and F24000350030002500kWh20001500100050001 2 3 4 5 6 7 8 9 10 11 12MonthsF1, IDA F1, EP F2, EP F2, IDAFigure 6.:Results, Spanish case 1, Energy Plus and IDA ICE

SUSREF34 (46)The total difference in the yearly heating energy consumption between Ida and Energy Pluscases is about 13 %. For some reason IDA calculates slightly lower heating energyconsumption than Energy Plus. This may be due to different initial data, or the use of somedefault values which have not been documented. Difference between cases with structures F1and F2 are very small, less than 1 % calculated with both IDA ICE and Energy Plus. Most ofthe difference seems to occur during the spring months. In IDA ICE cases the curve is smoothduring the spring months, in Energy Plus cases there can be seen an anomaly wheretemperature rises for a short period during the spring months. The difference can not beexplained with effects of the out door air temperature. Only thing that correlates with the timeof year are out door temperature and solar radiation. The temperature is represented in Figure5.: and there seems to be no such difference in the weather data that would explain thedifference. This could be a result of less solar radiation entering the building in Energy Pluscases, which may be as a result of the technical data or the way the simulation software takesthe solar radiation into account. Occupancy, lighting and equipment loads use the sameschedule through the year.6.1.2.5.3 Results, Norwegian caseThe following two tables present the results of the Norwegian case, simulated with bothEnergy Plus and IDA ICE.Table 13.: Results, Norwegian case 3, Energy PlusYht. 1 2 3 4 5 6 7 8 9 10 11 12kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWhHeat flux TO the building throughthe envelope 1 632 0 5 24 113 311 674 352 306 138 45 5 1Heat flux FROM the buildingthrough the envelope -4 209 -860 -750 -465 -214 -55 -2 105 -30 -36 -84 -297 -601 -777Sensible internal gains 18 495 1 030 930 1 023 1 007 1 023 3 6331038 1 023 999 1 030 9921038Latent internal gains 3 357 285 258 285 276 285 276 285 285 276 285 276 285Heat losses through infiltration 6 690 895 866 701 557 444 376 237 272 351 544 656 792Heat gains through infiltration 1 0 0 0 0 0 0 0 0 0 0 0 0Heat losses through ventilation 15 760 2 089 2 021 1 636 1 299 1 048 891 645 668 818 1 268 1 5301846Heat gains through ventilation 4 0 0 0 0 0 0 3 1 1 0 0 0Solar gains 11 740 171 388 800 1 309 2 099 1 9621760 1 450 896 611 197 97Heating loads 27 209 5 440 4 961 3 473 1 795 151 0 0 0 569 2 236 3 8084774Table 14.: Results, Norwegian case 6, IDA ICEYht. 1 2 3 4 5 6 7 8 9 10 11 12kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWh kWhEnvelope & Thermal bridges-11659 -1568 -1221 -1194 -889 -770 237 -734 -637 -542 -827 -1147-1417Internal Walls and Masses -46 -5 -6 -10 -16 -78 -34 -30 41 55 -6 -6 -7External Window & Solar 66 -887 -527 -125 274 777 773 736 512 220 -128 -601 -880Infiltration & Openings -30553 -4811 -3786 -3822 -2973 -1358 -605 -647 -629 -1360 -2612 -3519-

SUSREF35 (46)4348Occupants 2652 260 239 265 259 216 122 105 138 237 275 261 264Equipment 3978 338 306 338 328 338 188 337 338 327 338 327 337Lighting 2885 245 222 245 238 245 209 245 245 237 245 237 245Local heating units 32776 6433 4779 4310 2791 645 0 0 0 833 2721 4454 5810Heating energy, Norwegian case7 0006 0005 0004 000kWh3 0002 0001 00001 2 3 4 5 6 7 8 9 10 11 12Energy Plus IDA ICEMonthFigure 7.:Heating energy, Norwegian case, Energy Plus and IDA ICEThe difference of the Norwegian cases is about 20 %. The difference has divided quite evenlythrough the whole year and the curves are very much alike. Summer time, while there is noheating energy consumption, is in both cases the same length.6.1.2.5.4 Analysis of effects of the orientationAll cases simulated with IDA ICE were simulated in two orientations, long facades facing northand south (original case) and then turned 90°, long facades facing west and east. The resultsof the comparison are represented inTable 15.: Results, analysis of the effects of the orientationCase Total Jan Feb March April May June July Aug Sep Oct Nov DecNorway, Insulated wood frame, 0 ° 28310 5652 4161 3695 2320 519,5 0,4 0 0 674,4 2305 3881 5102Norway, Insulated wood frame, 90 ° 28581 5669 4191 3750 2384 534,6 0,4 0 0 697,2 2346 3899 5110Spain, Brick cavity wall, 0° 13528 3613 2454 1760 785 96 0 1 0 0 154 1705 2939Spain, Brick cavity wall, 90° 13599 3639 2471 1764 772 92 0 1 0 0 154 1724 2962Spain, Solid brick wall, 0° 13512 3617 2453 1757 786 96 0 1 0 0 151 1694 2938Spain, Solid brick wall, 90° 13585 3642 2471 1765 775 91 0 1 0 0 152 1710 2959The difference in all cases between 0° and 90° is less than 1 %.

SUSREF36 (46)6.1.2.6 Conclusions6.1.2.6.1 Yearly variationThe biggest difference in the results in all of the cases occurs during the spring time, fromFebruary to April-May. The trend is similar in both Spanish and Norwegian cases, even thoughin all cases some difference can be found during the fall months too. The difference during thespring months is bigger in the Spanish cases. During the summer months (April – August) theheating energy consumption is practically non existing in all cases, as it should be.The weather data is the same in all Spanish cases and in all Norwegian cases. The period ofthe occurrence highlights the differences in calculation methods of the windows and solargains and losses. In Energy Plus cases windows were defined in more detail than is possiblein IDA ICE. In IDA ICE it is not possible to see some values, such as the solar heat gaincoefficient, that are visible using Energy Plus.It may be thought that the reason for theobserved differences is the solar radiation processing way of both softwareds . More detailedinformation of the solar gains and losses would allow for this analysis, but this level ofinformation has not been available for IDA ICE.6.1.2.6.2 Infiltration and ventilationThe Spanish IDA ICE cases require 21-22 % more heating energy for ventilation than theEnergy Plus cases. In Norwegian cases the difference is a little larger, the IDA ICE caserequires about 30 % more heating energy for ventilation than the Energy Plus case (combinedventilation and infiltration).Since ventilation system has no mechanical heater, all makeup air comes as infiltrationthrough structures, and the schedules of ventilation and infiltration are the same, the effect ofthe ventilation and infiltration should be same in both IDA ICE and Energy Plus calculations.The weather files are identical therefore the difference cannot be explained with differenttemperatures of makeup air.One factor affecting the energy demand of ventilation could be the moisture contents of themakeup air. More detailed analysis of the calculation methods could reveal if there are somesignificant differences.6.1.2.6.3 Heat losses through constructionsThere may be some difference in the way gains and losses through constructions (includingwindows) are calculated in Energy Plus and IDA ICE. The way of reporting the results isdifferent, and comparing the factors of the heat losses is not therefore easy.The heating energy demand calculated with IDA ICE differs from Energy Plus resultssignificantly in both Spanish and Norwegian cases. In Spanish case IDA ICE result is onlyabout 50 % of the Energy Plus result and in Norwegian case , it is 270% % through thebuilding envelope.This raises many questions about the different definition of structures and effects of suchdetails on heating energy consumption. In Energy Plus cases the U-values of the structurescould not be verified. The structures were created by material layers and the technicalcharacteristics defined for the material layers. The final technical values of the constructioncan not be seen from Energy Plus, so e.g. the U-values cannot be compared. In IDA ICE thestructures were made as close to the definitions in Energy Plus cases as possible.For windows, in IDA ICE it is possible to define only U-value, solar heat gain coefficient, solartransmittance, visible transmittance and internal and external emissivity. In Energy Plus it ispossible to define glass thickness, solar transmittance, front and back side solar reflectance,visible transmittance, front and back side visible reflectance, infrared transmittance, front andback side infrared emissivity and conductivity.

SUSREF37 (46)6.1.2.6.4 Moisture transfer through constructionsWith Energy Plus, the moisture inside the construction can be calculated and the software hasmore functions for simulating the moisture transfer than IDA ICE does. IDA ICE takes theinternal moisture formation into consideration when calculating the heating energyconsumption, but the moisture in certain point of the structure can not be simulated.6.1.2.6.5 Energy Plus / IDA ICEThe comparison of the two software is complicated by the diversion in the way of presentingthe results. The grouping of the results is very different and effects of different factors are hardto isolate from the results. This may lead to different calculation attributes data in comparisonsimulations.There are no visual functions, as graphs or 3D or even 2D figures in the software, all the datais entered into tables. There are no library values and all the needed data has to be createdand inserted. Energy Plus is meant to be a simulation engine for a more visual interface and itis really not meant to be used independently.It is not easy to get a good picture of the initial data in Energy Plus. All the data has to bechecked separately and in cases the way of presenting the data is not clear, and e.g. thestructures are presented as coordinates, which makes it hard to see the shape of theconstruction and see if the coordinates have been defined correctly.IDA ICE is much more graphical and more information can be seen at a time. In IDA Ice too,there are quite many sheets of different functions of the software and it is quite easy to bypasssome critical information, but yet in IDA ICE there are some default values to be used if thevalue is not specifically defined. In Energy Plus there is no component unless one isspecifically created.Calculation methods are not easy to compare and they are not clearly visible from thesoftware interfaces. In IDA ICE it is possible to see the code and some explanations for whathas been calculated in each part of the code, but it is not a manual providing the calculationmethods. Also used calculation algorithms are not described in the user manuals of thesoftware. Energy Plus does offer more comprehensive manual and it includes informationabout the calculation methods.Energy Plus offers more functions for simulations and more flexibility, but it requires a gooduser interface or at least very advanced user to compete with other simulation software. At thesame time IDA ICE is more visual and easy to use, but changes are harder or not possible atall to make.7. At construction level7.1.1 Standards7.1.1.1 ISO 13788In general, EN ISO 13788, Annex A (CEN 2001) defines a simple method to assess the riskfor interstitial condensation within and on a surface of a building envelope construction. Itgives typical temperature and moisture loads for use in the calculation of constructions.These loads are typically given as monthly average values for outdoor air temperature, e.g. -5 C for January, etc outdoor relative humidity, e.g. 90% for January, etc indoor air temperature, e.g. 20C

SUSREF38 (46) indoor air moisture supply, e.g. 4 g/m 3 for T e < 0C and linearly decreasing to 0 g/m 3for T e > 20CThese boundary conditions can be used - and are widely used - for dynamic simulation of thebuilding constructions but it must be recognised that the standard is intended for steady-stateassessment of interstitial condensation using the Glaser method.If only thermal 2D/3D calculations are performed - e.g. with HEAT2 or Therm - (which arenormally sufficient for studying effects of thermal bridges), a method described in EN ISO13788 for calculation of critical temperatures of internal surfaces can be used for assessingthe potential for mould growth.Another standard EN ISO 15026 defines a more realistic presentation of the indoor conditionsthan the EN13788 as the indoor temperature in EN 15026 floats up to 25 degrees as afunction of outdoor temperature during the warm periods and is not fixed at 20 as in EN13788,which would require assumption of involving mechanical cooling.7.1.1.2 ISO 10211“ISO 10211: Thermal bridges in building construction - Heat flows and surface temperatures -Detailed calculations” is the base standard for the detailed numerical calculation of the linearthermal transmittance of thermal bridges.This standard models a specific building envelope area around the thermal bridge. This isperformed by selecting cut-off planes so that the impact of the thermal bridge is the same as ifthe entire building was to be directly calculated.Minimum distances between the cut-off planes and the investigated thermal bridge are set bythis standard, depending on the detail being studied . The required distances are of about 1m,if no simetry or basement area is involved.Figure 8.: Geometrical model of thermal bridges according to ISO 10211 [Source: ASIEPI P198]Concerning material properties, specific criteria are defined for thin layers, and materialproperty sources. Generally speaking recognized sources should be used, commonly ISO10456 or National building product catalogues.For air cavities, thermal resistances should be determined according to different standards(ISO 6946, EN 673 or ISO 10077, depending on the modelled building element).

SUSREF39 (46)Two sets of boundary conditions are referred to in ISO 10211: Boundary conditions for heat transfer analysis, referred to in ISO 6946. Boundary conditions for condensation risk assessment, referredo to in ISO 13766.This standard also sets test cases for thermal bridge software validation, both for 2- and 3-dimensional analysis.7.1.2 Tools and methodsBuilding physics is about understanding and analysing the heat, air and moisture (HAM)interactions - transport and storage - in and around building materials and constructions. Thiscomplicated theoretical analysis is typically implemented in more and more advancedsimulation and modelling tools. The simulation algorithms solve the coupled heat, air andmoisture (=hygrothermal) states throughout the control volume to be studied as a function oftime and place. Therefore, the dynamic simulations with hygrothermal simulation tools are animportant and even necessary part of the assessment work.Some of the most used and verified simulation tools for hygrothermal analysis of buildingconstructions are WUFI, DELPHIN and Match. In addition there are quite a few tools for purethermal assessment, mostly two or three-dimensional simulation tools for assessment of thethermal bridges like HEAT2, VOLTRA and Therm. However, coupled heat and moisturetransport need to be analysed in order to assess almost any moisture related performancecriteria.Simulation tools for building physical analysis at construction level can be divided in 2 groups:1. Tools for thermal analysis (H for Heat or HA for Heat and Air) and2. Tools for hygrothermal analysis (HAM for Heat, Air and Moisture or HM for Heat andMoisture).The first group represents typically numerical models for steady state or dynamic presentationof the temperature field in 2 or 3 dimensions. These tools are typically used for analysis andoptimation of thermal bridges.The models in the second group solve the dynamic and coupled heat and moisture transportequations. These models are used typically for analysis of the hygrothermal performance ofthe critical parts of a building construction.7.1.2.1 WUFIWUFI is a commercial tool for dynamic hygrothermal analysis of constructions that is widelyused both by the researchers and practitioners. It includes most of the basic transportphenomena and it is relatively easy to use.WUFI, as all the simulation tools for hygrothermal analysis, considers usually at least watervapour diffusion that is transport of moisture in the air, typically in the pores of a material. Thisis the predominant transport mechanism in a very porous material (e.g. mineral wool). If thepores of the material are very microscopic (e.g. concrete) and/or the material is very wet (e.g.wet wood), the capillary conduction will be dominating. This capillary transport is included inWUFI as well as in other tools like DELPHIN and Match.Convective moisture transfer takes place in air gaps of a construction and in very open porousmaterials like light weight insulation materials. The driving force can be the air pressuredifference due to the temperature gradient within the material that enables natural convection.

SUSREF40 (46)Or the convection can be forced by air pressure through any air leakages in the envelope.Hygrothermal convection is normally modelled physically correctly only in the most advanced2D tools, like WUFI 2D.There are 2 different versions of WUFI:WUFI-Pro 4 : A 1D coupled heat and moisture calculation tool that is the best choice forconstructions and solutions consisting of just homogenous layers. Problems withsimple ventilated cavities, however, can be studied simplified with this tool to someextendt. WUFI2D: A 2D coupled heat and moisture calculation tool should be used forconstructions containing inhomogeneous layers, e.g. stone walls, fastenings, andventilation cavities. 3D effects must be taken into account by qualified modification ofthe model, together with a possible 3D thermal calculation.Constructions with complicated cavities or elements with active fluids like air or water/brine orreflective surfaces should be modelled with multi-physics or CFD-tools (Computational FluidDynamics tools) (e.g. Comsol 5 , Fluent 6 ) and not with WUFI.Generally, a one-dimensional (1D) HAM-tool like WUFI Pro is sufficient for most of theanalysis with skilled expert use. The computation of coupled heat and moisture transport intwo dimensions (2D) is usually very time-consuming and the detailed information from a 2D oreven 3D calculation may be overruled by other uncertainties. Pure heat transmission tools (in2D and 3D) are very usable for optimisation of the thermal bridges and assessment of thecritical surface temperatures for e.g. mould risk.The simulation output from WUFI is typically the temperature and moisture content statesthroughout the defined construction as a function of time. This output can be then postprocessedin order to give input for the assessment.7.1.2.2 KobraKOBRA is a computer program containing an interactive thermal bridge atlas. This atlasprovides the 2-dimensional steady-state thermal bridge behaviour of specific building details.This program is somewhere betweeen actual thermal bridge atlases such as the acreditedconstruction details (UK) and fully free-modelling thermal bridge programs like THERM.Although its DOS interface is outdated, KOBRA is an interesting tool for building designersdue to its simplicity in use and fast access to results, which moreover are accurate and failsafe.The EUROKOBRA software provides the following results:A section displaying the inside surface resistance Rsi, the inside surface coefficient hi (=1/Rsi)and the boundary temperatures (i and e) used in the condensation and the heat lossevaluation. As according to most regulations, different Rsi/hi-values should be used to modeleither a condensation risk or heat loss, the user has to edit the boundary condition and torecalculate the evaluation. However, in most cases, the results of the heat loss evaluationobtained using the Rsi/hi-values for condensation risk evaluation have a reasonable accuracy.4 http://www.wufi-pro.com/. The simulation tool is based on the PhD dissertation: Künzel H.M.:Verfahren zur ein- und zweidimensionalen Berechnung des gekoppelten Wärme- undFeuchtetransports in Bauteilen mit einfachen Kennwerten; Dissertation Universität Stuttgart 1994.5 http://www.comsol.com/6 http://www.fluent.com/

SUSREF41 (46)The condensation risk evaluation for up to 3 points on the inside surface of the detail (typicallysymbols K, L, O), the temperature factor, the surface temperature and an evaluation of thecondensation risk.It should be mentioned that KOBRA only evaluates two-dimensional thermal bridges. Threedimensionalthermal bridges are possibly more sensitive for condensation risk.The heat loss evaluation: the U-values [W/m2K] of the flanking elements, the total heat loss Q[W/m] through the building detail, as well as other heat transfer coefficients such as thecoupling coefficient Lie [W/mK], the linear U-values psi-i and psi-e [W/mK] and the mean U-value Um [W/m2K].KOBRA is arranged as a series of building detail collections, each of which contains up to 16details. A report with a thermal bridge analysis is provided for each of these details. Theflexibility of KOBRA lies in the facts that the detail can be edited, by modifying its dimensions,materials and boundary conditions, automatically recomputing the temperature field using anaccurate energy balance technique. Therefore, isotherms and heat flow lines can berepresented in a clear way.The EUROKOBRA database contains 9 sections: massive walls without insulation massive walls with outside insulation massive walls with inside insulation partially insulated cavity walls fully insulated cavity walls light wooden constructions window frame sections simplified details according to PrEN/ISO 14683 (July 1996) didactic examplesThe first six sections, the other being particular cases, contain about 40 to 50 atlas pages ofwhich the names refer to the type of the building details in it. The following types may occur: Wall, horizontal section, no window Concrete column in wall section Window connection in horizontal wall section Foundation Floor-slab to wall connections Overhangs Flat roof sections Pitched roof sectionsterrace including window connections Balconyes includingwindow connections

SUSREF42 (46)7.1.2.3 ThermTHERM is a state-of-the-art, Microsoft Windows-based computer program developed atLawrence Berkeley National Laboratory (LBNL) THERM is a two-dimensional heat-transfermodelling software focused in building components such as windows, walls, foundations,roofs, and doors; appliances; and other products where thermal bridges are of concern. Heattransferin THERM is based on the finite-element method, which can model complicatedgeometries in building products. Heat-transfer analysis in therm provides a product’s heattransfer coefficient and its local temperature patterns, which are relatd to problems such ascondensation, moisture damage, and structural integrity.THERM is part of a wider software package called WINDOW, which is focused on heat andradiation transfer through windows and glazed areas, also under continous development byLBNL. THERM's results can be used with WINDOW's center-of-glass optical and thermalmodels to determine total window product U-factors and Solar Heat Gain Coefficients.Figure 9.: Temperature distribution in a Curtain Wall [Source: TECNALIA]THERM has three basic components:Graphic User Interface: A graphic user interface that allows the drawing of crosssections of the product or component evaluated.Heat Transfer Analysis: A heat-transfer analysis component that includes: anautomatic mesh generator to create the elements for the finite-element analysis, a finiteelementsolver, an optional error estimator and adaptive mesh generator, and an optionalview-factor radiation model.Results: A results displayer.THERM has standard graphic capabilities associated with the Microsoft Windows operatingsystem. THERM has powerful drawing capabilities that make it easy to model the geometry ofthe cross section of a building component. Direct geometry drawing as well as DXF or bitmapimparting capabilities are availabe.

SUSREF43 (46)The following thermal properties must be defined for the cross section geometry:Material properties (broken into two classes: solids and cavities) of eachcomponent of the cross section,Boundary conditions at the external edges of the cross section.THERM uses two-dimensional (2D) conduction and radiation heat-transfer analysis based onthe finite-element method, which can model the complicated geometries of fenestrationproducts and other building elements. This method requires that the cross section be dividedinto a mesh made up of non-overlapping elements. This process is performed automatically byTHERM using the Finite Quadtree method. Once you have defined the cross section’sgeometry, material properties, and boundary conditions, THERM meshes the cross section,performs the heat-transfer analysis, runs an error estimation, refines the mesh if necessary,and returns the converged solution.The results from THERM’s finite-element analysis provides the following data:U-factors,isotherms,color-flooded isotherms,heat-flux vector plots,color-flooded lines of constant flux,temperatures (local and average, maximum and minimum).