INSULATION; HEATING, VENTILATION & SERVICES 65


Of course, creating energy-efficient buildings is not only about the level of insulation used. Solid concrete wall construction also ensures good levels of airtightness – as low as 0.3 m³/hr.m² and superior thermal bridging performance with Y-values as 0.02 regularly being demonstrated using certified junction psi values. This is a critical factor in their outstanding thermal performance, achieved when combined with their inherent air tightness and low U-values. This results in even temperatures throughout the structure with reduced draughts and cold spots enabling the building to stay warm in the winter and cool throughout the summer.


Energy efficiency in practice A great example of ICF’s potential is The Curly House by Nudura. The client’s brief was to rebuild an existing cottage to Passivhaus standards to minimise their energy consumption and carbon footprint while also meeting planning restrictions faced when building in an Area of Outstanding Natural Beauty. The energy efficiency challenge was even greater when working on a highly exposed site


subjected to bitingly cold winters and very hot summers. The design by architects Ecotecture consists of a crescent-shaped detached home which steps and slides into the slopes of the site and features a curved brise soleil.


Nudura was specified for the walls with a thermally broken super-insulated deck system that would take a load of 5 kN/m. The heavier construction option was chosen to provide thermal mass that balances the heating gains and losses due to the large areas of glazing. The insulating element of Nudura’s ICF acts as a buffer to the thermal mass allowing the slow release of heat into the building to ensure a constant internal temperature throughout the year. The semi-subterranean nature of the design also meant that the build materials had to withstand a damp environment – ruling out the option of timber.


The finished design and ICF have made it possible to reduce thermal bridging to a minimum with the enhanced air-tightness standards required for Passivhaus compliance.


Christopher Stride is chairman at Insulating Concrete Formwork Association


© Beco Wallform


Curly House © Nudura UK


ADF NOVEMBER/DECEMBER 2024


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