Concrete Today May 2010 - the Irish Concrete Federation

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concrete today - icfai Insulating Concrete Formwork Wall Insulating Concrete Formwork Upper Floor Insulating Concrete Formwork, is a permanent shuttering for the construction of concrete walls and floors. The formwork remains in place after the concrete is poured, as a permanent part of the wall assembly. The insulating formwork acts as thermal and sound insulation and in some systems is dovetailed to receive dry-lining on the inside Insulating Concrete Formwork House and plaster on the outside. The external render is comprised of a waterproof, mineral based render which is applied to a loose weave fabric mesh for adequate adhesion. ICF’s have a number of benefits including the virtual elimination of cold bridges, low air filtration, high thermal performance and dimensional accuracy. Panelled roof systems, with co-extruded steel stiffening members within the panel are also available. These panels are battened and counter-battened top and bottom for slating on top and to carry plasterboard on the underside and look identical to the traditional cut roof or trussed roof when completed. By eliminating timber trusses, and replacing them with reinforced polystyrene panels, cold bridging in the roof is virtually eliminated. ICF walls can be reinforced or un-reinforced depending on the loading requirements. Concrete beams, spanning window and door heads, can be easily constructed by inserting re-bar into the formwork prior to pouring the concrete. When the concrete is poured, the ICF walls can be subject to high levels of hydrostatic pressure, particularly if the mix is too wet. A 25N mix with a 10mm rounded stone is normally specified. To prevent misalignment of the walls the formwork is braced prior to the concrete pour. Proper bracing of the ICF is crucial to ensuring that the ICF walls are plumb. For further information contact the Irish Concrete Federation or alternatively contact the ICFAI companies direcly: The members of the newly formed ICFA are: Amvic Ireland, Naas, Co. Kildare Tel: 045 889276 Clantec, Future Build Systems Ltd., Portarlington, Co. Offaly Tel: 057 8645000 Kore, Kilnaleck, Co. Cavan Tel: 049 4374000 Minimum Carbon Konstruction, Scotstown, Co. Monaghan Tel: 047 79792 Thermohouse, Coolcaslagh, Killarney, Co.Kerry Tel: 064 6631307 Warmbuild (Authorised Nudura Distributor) Tel: 057 8627318 concrete today 16
concrete today -zero carbon emissions Concrete Moves towards Zero Carbon Emissions By Liam Smyth FIEI, Sustainability and Marketing Manager, ICF In a previous article for Concrete Today, the initial design and early stages of construction of Ireland’s first Zero Carbon Emissions Concrete House were discussed. Now, as the project nears completion, key aspects of achieving the design targets as well as lessons learned are reviewed. Design Overview Originally designed to Passive House standards (and an A3 BER Rating in this case), the Irish Concrete Federation became involved in the project prior to construction, having agreed with the owner/builder the much higher targets of Zero Carbon Operational Emissions (from primary energy needs) and an A1 BER Rating (0-25 kWh/m² per annum for primary energy). Target U values of 0.1 W/m²K were adopted for the ground floor, external walls and roof, while an overall U value of 0.8 W/m²K was specified for windows. Outstanding thermal bridging performance was required, ever harder to achieve in a super insulated house, by the specification of a Y value of 0.04 W/m²K. General Construction Details Achieving these targets required very close attention to detail by both designer and builder as energy performance and constructability do not always go hand in hand. The foundation detail chosen was a raft foundation which is completely underlaid with EPS, with 200kPa non-compressive EPS under the beam sections and 100kPa specified under the floor areas. This minimises heat loss through the floor Window fixed with external brackets Zero Carbon Concrete House and substantially eliminates the thermal bridging heat loss problems associated with traditional strip and raft foundations directly in contact with the ground. Wall construction is a standard heavyweight block laid on the flat (215mm thick), plastered internally with EPS on the external face with a suitable render. While these details are similar to type 2 wall construction as per the Acceptable Construction Details, published by DEHLG in late 2008, thermal bridging performance is achieved by windows and doors being cantilevered into the external insulation on simple stainless steel L brackets, in addition to the enhanced foundation details. At roof level, a warm roof detail whereby EPS is placed above, between and below the rafters was chosen. At eaves and gables, the insulation meets the external wall insulation to complete the insulation envelope. So, while overall a fairly simple build in principle, the devil is in the detail. Substantially, a direct build by the owner/ builder, technical expertise was provided by Aerobord Ltd., the chosen insulation supplier, and CPI Ltd., whose Baumit system was the chosen external render. Getting Foundations Right Working from a levelled base of Cl804 aggregate, blinded with sand and covered with a radon barrier which also acts as a damp proof membrane, overlaid with the appropriate EPS grade for the location. The outside of the raft was timber formwork with all internal support for beam sections formed with EPS panels in place to provide the floor insulation. While this led to increased use of insulation, it saved on time and added certainty to the process, ensuring exact coverage and minimal thermal bridging. As built, the floor U value achieved was 0.09 W/m²K, even better than the design target. Of substantial overall importance is to bring all service pipes, e.g. sewers, water, electricity, air ducts, through the foundation to avoid breaking the insulation envelope above ground. All such piping was wrapped in insulation throughout the foundation to minimise thermal bridging. This complicated the foundations somewhat and is a plumber’s nightmare (given a lack of internal walls for guidance) but serves the project targets well. The raft, when poured, can then be power floated to leave the finished floor, thereby saving time later in the project. CEMEX (Ireland) Ltd.supplied the readymix concrete for the pour, using a low carbon 30N mix. The same company later supplied the blocks and first floor structural screed. Walls and Intermediate Concrete Floor In building a 215mm block wall, it is important to ensure that it is well jointed with mortar, to minimise air permeability, and kept smooth externally, to ensure the external insulation can be fitted correctly. concrete today 17
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Concrete Today May 2010 - the Irish Concrete Federation

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