Kilbroney Timber Frame Ltd has just completed a large passive project in Delgany, Co Wicklow. Passivhaus or passive house is a voluntary industry standard that results in buildings which require little or no energy use for heating or cooling. They have excellent internal thermal comfort and low primary energy use. U-Values for the walls, ground floor and roof were maximum 0.15 W/(m²K). Two independent stud walls were formed in order to provide sufficient thickness for insulation and to limit cold bridging.
Air tightness was key to this buildings success and great care and attention to detail were critical as we had to reach passive house institutes famously tough standard of 0.6 ach -1 @50Pa [~1.5m³/(m²h)]
For the windtight layer externally we used Kilbroney membrane and Wigluv tapes from Siga. All Siga’s exterior products have been certified as driving rain proof by the TU Berlin Technical Institute. The roofing membrane was also taped and sealed insuring the external envelope of the dwelling was not only rain proof but also wind proof.
Eliminating cold bridging is particularly important in passive design. We had to ensure that the double wall formed to make the external walls had no studs lining up. Construction free of thermal bridging, Psi maximum 0.01 W/(m²K) was achieved.
We designed and built this passive energy house to ensure the owners get outstanding performance.
This dwelling consisted of the following features.
The External Timber Frame Walls had two separate 2 walls – 38 x 89mm studs & rails positioned at 600 centres with 9.2mm panelvent sheathing board & Breather paper, 100mm cavity, 38 x 140mm studs & rails positioned at 600 centres with 18mm OSB sheathing board. The total width of the timber frame was 356mm. The studs within both frames were staggered to further reduce thermal bridging, the laps in the breather paper where taped with Siga Wigluv external tape to make the building envelope wing tight.
The roof was to be left wind tight also; we fitted 9.2mm Panelvent to the roof and then fitted felt & lath. The felt overlaps where taped with Siga Wigluv external tape.For the finish to the roof we fitted a black natural slate. The first layer of breathable roofing membrane was laid with all joints tapped. The bottom layer of the roofing membrane was taped to the wall membrane making the house wind tight.
The floor Joists where positioned at 400 centres with 18mm OSB flooring.
The dwelling we have built will strive to achieve and surpass the set targets
• Space heating demand of less than 15 kWh/m²/year
• Maximum heating load of 10 W/m²
• Cooling demand of less than 15 kWh/m²/year
• Primary energy use of less than 120 kWh/m²/year (heating, lighting, domestic hot water, appliances)
• As-built air tightness of less than 0.6 ach-1 @ 50Pa [~1.5m³/(m²h)]