Passive House in Canterbury Ensures Low-Energy Living

One of the owners works for a supplier of high-performance building components and well understood the “massive benefits” such a house would provide his young family. His professional experience with multiple Passive House projects also contributed to a very smooth design and build process. Although the project was extensively documented in video, there was no drama to see here.

There was excitement though: like when the bulk of the house was erected in just one and a half days. The project used structural insulated wall panels pre-fabricated by Ecopanel near Christchurch. These are a custom-made, modified timber frames that arrive on-site complete with structural facing, a rigid air barrier, insulation, Intello air-tight membrane and service cavity. The panels were erected onsite directly off the back of the loader crane they arrived on. The house stands on a MAXraft concrete slab. Windows were manufactured in Mosgiel using European glazing. As to be expected this far south, triple-glazing was required, in this case with low-e coating and argon fill.

The owners had a modest budget and wanted their house to demonstrate that Passive House performance is within the reach of middle-income families. Its simple form and moderate size (166m² TFA, excluding a detached double garage) helped the building meet Passive House energy targets; it still provides three bedrooms, two bathrooms and a home office. A veranda encircles 70% of the house, softening the rectangular shape and providing outdoor living areas that are easily accessible through 2.2 metre-high by 3.6 metre-wide sliding doors. The owners are enjoying their second winter in their first home. Christchurch can have very low sunshine hours in the winter months, so they are using more heating than they initially expected. However, a small panel heater sized for a bedroom is providing all the additional heat they need to keep the whole house comfortably warm.

Construction Details Average Values:

U-value External Walls 0.20 W/(m2K)(R5.0)

Shadowclad, 19mm cavity, Ecoply Barrier, 140mm framing with 90mm R2.8 Knauf and 50mm R1.4 Knauf, Intello, battens with R1.4 Knauf, 12mm plasterboard

U-value Floor 0.15 W/(m2K)(R6.7)

MAXRaft insulated foundation system, 100mm concrete over 250mm EPS-s. Tie beam with 250mm concrete and 100mm Expol XPS

U-value Roof 0.13 W/(m2K)(R7.7)

colorsteel, 70mm cavity (45mm battens over 25mm counter battens), Proclima Solitex mento, 280mm framing with R6.3 Knauf, Intello, battens with R1.4 Knauf, 40mm cavity, 12mm plasterboard

U-value Glass 0.55 W/(m2K)(R1.8)

Thermadura Silverstar

U-Windows 0.94 W/(m2K)(R1.1)

Thermadura Natureline

Ventilation Efficiency 81.50%

Zehnder - ComfoAir350

Heating Demand 24.9 kWh/m²/year
Heating Load 9.4 W/m²
Frequency of Overheating 2% year over 25°C TFA 166 m²
Form Factor 3.2
Air leakage @ 50Pa0.3 ACH/hour
PER demand55 kWh/m²/year

Passive House Database 5299

Roof Underlay (SOLITEX MENTO 3000)

pro clima

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SOLITEX MENTO 3000 roof underlay is a three-layer roof underlay designed to be used with most typical roof cladding systems. While providing temporary weather protection it can remain exposed for up to 90 days.

SOLITEX MENTO 3000 has been appraised for use as a self-supporting roof underlay on buildings within the following scope:

the scope of limitations of NZBC Acceptable Solution E2/AS1, Paragraph 1.1 with regards to building height and floor plan area; and,
with masonry tile roof cladding; and,
with metal tile and profiles metal roof cladding; and,
suited to NZS 3604 Wind Zones up to, and including Extra High.

In the opinion of BRANZ, SOLITEX MENTO 3000, if used, designed, installed and maintained in accordance with the statements and conditions of the BRANZ Appraisal, will meet, or contribute to meeting the following provisions of the NZBC:

Clause B2 DURABILITY: Performance B2.3.1(a), not less than 50 years, B2.3.1(b), 15 years and B2.3.2 SOLITEX MENTO 3000 meets these requirements. See Paragraphs 9.1 and 9.2 of the BRANZ Appraisal.
Clause F2 HAZARDOUS BUILDING MATERIALS: Performance F2.3.1 SOLITEX MENTO 3000 meets this requirement and will not present a health hazard to people.
Clause E2 EXTERNAL MOISTURE: Performance E2.3.2 When used as part of the cladding system, SOLITEX MENTO 3000 will contribute to meeting this requirement. See Paragraphs 12.1 and 12.2 of the BRANZ Appraisal.

BRANZ Appraised

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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