Airtightness Layer Contributes to Low Energy Rotorua Home

Ian and Raewyn Simpson subdivided the Rotorua section that they have lived on for over 24 years, in order to build their dream home. They wanted a home that would be comfortable all year round with low running costs for heating and cooling, as well as having the latest in home automation.

The couple chose a local Rotorua builder, AJ from Performance Build, based on his experience building low energy homes.

In order to create a high-performance envelope, they used Knauf Insulation to achieve R4.1 insulation in the walls. In the ceiling, they used the Knauf Jet Stream MAX blown-in insulation product.

An INTELLO Plus airtightness layer was installed in order to maximise the performance of the insulation and minimise energy losses. A blower door test was performed and the home achieved an airtightness level of 1.3 ACH (air changes per hour). To put that number in context, average new builds in NZ achieve between 5 and 8 ACH at 50 Pascal’s. A Zhender HRV system will ensure that fresh air is delivered to the home year-round at the right humidity levels, with efficient heat recovery being possible with the airtight envelope.

Double glazed UPVC windows and doors from NK Windows were installed, which include tilt and turn hardware for maximum functionality. Windows are the biggest weakness in a building's thermal envelope, and the Simpsons recognised the need to use better performing joinery to ensure their desired outcome.

A Maxraft fully insulated slab was chosen to complete the envelope.

An Ata Touch home automation system will allow for automation of the lights, blinds, wall panel heaters and security alarm all from a mobile app remotely.

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

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