First Passive House in the Bay of Plenty

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

Intelligent Airtightness Membrane (INTELLO PLUS)

pro clima

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The pro clima airtightness system prevents uncontrolled air infiltration or leakage through the building envelope, and assists the drying capacity of the building through its unique moisture control properties.

Suitable for all construction and where there is risk of interstitial condensation
The protection of insulation from air movement
Preventing uncontrollable air flow though the building envelope
An optional continuous cavity for electrical and plumbing services can be created on the inside face of the external wall by fixing battens horizontally over the INTELLO membrane before installing the wall lining
The main advantage of a service cavity is to shift the plumbing and wiring out of the insulation layer
A service cavity also reduces the penetrations through the airtightness membrane allowing easy and fast installation of services
This also eliminates pressure points on inner lining (eg. plasterboard) from insulation expansion

The NZBC requires only that airtightness be considered, not measured. INTELLO directly assists with meeting the following requirements:

Clause E3.1 INTERNAL MOISTURE: Buildings must safeguard people against illness, injury, or loss of amenity that could result from the accumulation of internal moisture
Clause E3.2 INTERNAL MOISTURE: Buildings must avoid the likelihood of fungal growth or the accumulation of contaminants on linings and other building elements
Clause E2 EXTERNAL MOISTURE: Concealed spaces and cavities in buildings must be constructed in a way that prevents external moisture being accumulated or transferred and causing condensation, fungal growth, or degradation of building elements
Clause E2 EXTERNAL MOISTURE: Building elements must make due allowance for the following: (a) the consequences of failure, (c) variation in the properties of materials and in the characteristics of the site
Clause E2 EXTERNAL MOISTURE: Interior linings with all joints stopped require barriers to airflow
Clause H1 : ENERGY EFFICIENCY: The building must be constructed to limit uncontrollable airflow
Clause H1 : ENERGY EFFICIENCY: Account must be taken of physical conditions likely to affect energy performance of buildings; (c) Airtightness of the building envelope.
Clause B2 : DURABILITY: Performance B2.3.1(a), not less than 50 years, B2.3.1(b), 15 years and B2.3.2

BRANZ Appraised

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