The first Certified Passive House Plus in the Bay of Plenty is delighting its owner/builders with the quiet comfort it offers. They’re also delighted with their power bills, which have dropped from $160+/month to a monthly average of $32 over the year. Heating demand and load performance are well below Passive House maximums and minimal energy is used for cooling.
Timber windows from Thermadura were chosen for their looks and performance; approximately 20dB noise reduction also delivered by the double-glazing with low-e coating and argon fill is much appreciated.
The owners are a certified Passive House consultant and experienced builder respectively who designed and built the house themselves. Their goal was an affordable, low-maintenance family home. The 145m² (treated floor area) two-storey house has three bedrooms, two bathrooms and a multi-function room downstairs, which variously serves as an office, spare bedroom and media room.
The house is a timber construction with 140 x 45mm studs at 600mm centres and an additional 50mm of insulation in the service cavity. The airtightness layer was created using INTELLO Plus from pro clima. The suspended floor is timber-framed and insulated with fibreglass and polyester insulation (with wind wash backing that ensures the thermal performance of the insulation is not compromised by air movement).
The mid-floor used hyJOIST, a locally engineered wood joist that is lightweight and strong. The joist hangers are fixed to the stringer on the external walls with a lot of engineered fixings that penetrate the air-tightness layer. This caused some concern during construction but the impressive air blower door test gave assurance that performance wasn’t compromised.
Zehnder heat recovery ventilation was chosen because it is Passive House certified and the owners valued the support provided by the local suppliers.
The couple are already looking forward to more Certified Passive House builds.
Heating Demand: 10.4 kWh/m²/year
Heating load: 8.4W/m²
Frequency of overheating: 3.6% year over 25°C
Air leakage: @ 50Pa0.5 ACH/hour
PER demand: 26 kWh/m²/year