The first Certified Passive House Plus in the Bay of Plenty is delighting its owner/builders with the quiet comfort it offers. Heating demand and load performance are well below Passive House maximums and minimal energy is used for cooling. This has seen the owers’ power bills drop from $160+ per month down to a monthly average of just $32 for the year.

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 145 m² (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 45 mm studs at 600 mm centres and an additional 50 mm of insulation in the service cavity. The airtightness layer was created using INTELLO® PLUS Intelligent Air Barrier 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 airtightness 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