Energy Efficiency in Conservation Areas - Westminster City Council

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InsulationEnergy Efficiency in Conservation AreasMaterialsEnergy Efficiency in Conservation AreasKey PrinciplesInsulating a building envelope is essential toimprove energy efficiency. Adding or increasinginsulation to floors, walls, roofs and increasing thethermal performance of windows and doors (seepages 9 & 10) can be achieved in various ways.The choice of technique will depend on theconstruction of the building, on cost limits and onplanning restrictions.When installing insulation the following keyprinciples should be followed to ensure GoodPractice, to achieve maximum energy efficiencyand cost effectiveness:• Carry out insulation as part of anintegrated energy efficiencyrefurbishment strategy;• Use as much insulation as possible -generally the benefits increase withinsulation depth;• Ensure by dew-point calculation thatinterstitial condensation will not occurwithin the construction;• Ensure that the insulation is continuousparticularly at floor, wall and roof junctionsso that thermal bridging does not occur(see page 5);• Ensure that the method of insulation doesnot cause or aggravate rot or dampnessproblems;• Use insulation with Zero Ozone DepletionPotential (ZODP) to prevent contributingto global warming.Ground Floors & BasementsGround floors are responsible for a significantamount of heat loss, up to 10%, so insulationshould be considered during refurbishment work.Planning guidance is given on page 6.Raising floors is undesirable where it disturbsoriginal features such as stone or tiling, or involvesaltering existing doors, staircases and lift access.However, some methods allow original floors andlevels to be maintained or rebuilt. Alternatively,external perimeter trench insulation can be used.Solid floor insulation• is normally cost effective if replacing afloor or existing screen, which avoidsraising floor levels• can be placed under the slab if replacinga floor, which allows a solid floor finish tobe built• can be placed above the slab, topped byboards, in place of an existing screen (seeabove)• needs technical advice if working withoriginal floors e.g. stone, earth or limeconcreteSuspended floor insulation• normally easy & worthwhile if accessavailable from below, or if renewingfloorboards (see left)• raises floor levels when added on top ofexisting timber floors with battens andnew boards• needs draughtstripping between floor,skirtings & panelling with ventilation tovoids underneath• should use open jointed boards or nettingto support insulation and avoid trappingspilt liquidsInsulationAll insulants should have zero ODP. Someinsulants, e.g. some cavity wall insulationmaterials have health hazard concerns, otherssuch as mineral fibre, use large amounts ofenergy in their production: up to 30 times that ofsheep wool. Other natural materials such as hempand flax are available and cork (see top right) isalso appropriate for use in flat roofing. Recycledcellulose insulation (see middle right) can be usedin roofs and suspended floors.PVC-free buildingsThere are significant concerns about thesustainability of PVC products in terms ofpollutants, longevity, maintainability and disposal.It is possible to produce sustainable PVC-freebuildings, with timber windows and doors, castiron rainwater goods, LSF or OHLS cabling andclay drainage.Transport of materialsAs with labour and skills, it is important to uselocally sourced materials wherever possible, toreduce the pollution arising from and the energyinvolved in the transport of bulky buildingmaterials.Repair and reuseGood design and detailing and the repair orreplacement with like for like ensures that thebuilding performance is not affected. Use recycledor reused materials wherever possible but ensurethat they are sourced from a reputable supplier.Materials & construction adviceThe AECB ‘Greener Building’ directory is a goodsource book for the environmental selection ofmaterials. ACTAC produce the ‘Green BuildingDigest: a guide to building products and theirimpact on the environment’. The BRE producevarious publications concerning the environmentalselection of materials, such as ‘The Green Guideto Specification’ and produce numerous GoodPractice Guides such as that opposite. SeeContacts on the back page for all of the above.3 16
MaterialsEnergy Efficiency in Conservation AreasInsulationEnergy Efficiency in Conservation Areas15Key PrinciplesBuildings constructed with traditional materialsoften have no DPCs, impervious membranes orfinishes that modern buildings rely on. Moisturecan be absorbed by the fabric and released againwhen better conditions prevail: this is oftenreferred to as ‘breathing’ construction. Furtherdetail is contained in SPAB Information Sheet 4‘The need for old buildings to breathe’, seeContacts on the back page.Poor choice of materials and improvements canhave a significant impact on building performance,exacerbating damp problems and acceleratingdeterioration. SPAB have a number of technicalpamphlets giving relevant advice. In addition,there is often a greater energy input in the form ofheating, ventilation and dehumidification as aresult. Damp walls do not retain heat and willincrease heat loss.It is Good Practice when renovating traditionalbuildings to introduce replacement materials thatare similarly ‘breathable’. When extending inmodern materials and carrying out refurbishmentworks at the same time, two separatespecifications are needed.Materials can have a significant impact on theenvironment and the health of occupants. Beforechoosing a material, please consider:• the source of its original raw materials• manufacturing processes• transport of resources and products• the impact on a building and its occupants• the issues surrounding removal anddisposalA number of subjects are discussed below inrelation to the above issues.Lime mortarThe porosity of lime and earth based mortar andrenders permits evaporation of moisture fromwithin the wall. The application of cement pointingand renders on traditional walls is largely nonporousand may lead to damp, rot anddeterioration. Lime and earth based mortars arewidely available, use less energy in theirproduction and can easily be removed frombuildings allowing recycling and reuse.TimberAll timber used in building and finishing should besustainably sourced. The Forest StewardshipCouncil (FSC) runs a credible certification schemeto label such timber (see Contacts). Leadingcampaigners advise that other certificationschemes should be approached with caution.They should have objective and measurablestandards, demonstrate a credible chain ofcustody and have a system for independentassessment or audit.Timber products that use glues e.g. particleboards can contain VOCs which should beavoided.Timber treatmentIt is usually advisable to seek professional advicefrom a suitably experienced architect or surveyorbefore employing the services of a commercialcompany. In many cases, prevention by gooddesign and maintenance is better than a cure. Theunnecessary destruction of fabric and use ofchemicals is often unjustified.A number of publications are available, such as‘Timber Decay in Buildings: the conservationapproach to treatment’ by Brian Ridout, EnglishHeritage & Historic Scotland in association with E& F Spon (ISBN 0 419188 20 7). English Natureshould be contacted where any proposed workscould put bats or wildlife at risk.Paints & stainsLimewash was widely used to decorate buildingsinternally and externally. This is a porous materialand is still available. Modern petrochemical paintsform a barrier to moisture and exacerbateblistering, condensation and mould problems.Organic-based paints and stains are porous andare much less polluting or toxic in theirmanufacture, application and to the occupants of abuilding.Further information on the health hazards of paintscan be obtained from the London Hazards Centre(www.lhc.org.uk). Materials such as oak can beconsidered, which do not require paints or stains.Figure 1New concrete ground slab with insulation beneath(replacement floor to existing levels)Figure 2Concrete ground slab with insulation and boardsover (replacement screen to existing levels)Key to Figures 1- 41 Insulation with ZODP (flooring grade in Figs1&2)2 Perimeter insulation to new slab and screen3 DPM laid to overlap DPC in wall4 New timber boards can be supported onbattens5 Draught-sealing around internal wall insulationFigure 3Suspended timber floor with access from below(existing boards and levels)Figure 4Suspended timber floor with access from above(replacement boards to existing levels)6 Support netting fixed to underside of existingjoists7 Perimeter insulation to be used whereverpossible8 Draught-sealing between skirting and floorboards(particularly if no wall insulation as item 5)9 Support netting laid over joists from above4
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Energy Efficiency in Conservation Areas - Westminster City Council

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