Building sealing verification

The NCC is a performance-based code.

It requires all houses to make efficient use of energy, particularly the energy required for cooling and/or heating.

An important aspect of this requirement is sealing the building envelope to minimise air leakage.

There are two pathways for demonstrating that the building envelope is sealed adequately and meets the NCC Performance Requirement.

One is to follow the prescriptive Deemed-to-Satisfy Provisions in the NCC…

…but if that's considered too rigid or not appropriate for a particular building design, a Performance Solution can be used to demonstrate compliance.

The Verification Method for building envelope sealing is an Assessment Method that may be used as one such Performance Solution.

It offers flexibility to assist in creating an innovative built environment, and allows designers to decide the most appropriate methods of construction for their project.

This method demonstrates compliance through practical testing.

The required performance level matches a typical house, built in accordance with the prescriptive Deemed-to-Satisfy Provisions.

There are five steps to use this Verification Method.

Step 1 – Planning.

This method requires verification through testing. This is done immediately after construction of the building envelope is completed.

Plan your program of work, as well as those of tradesmen or contractors, so they are adequate to do the testing and complete any remediation that may be required.

Step 2 – Complete construction of the building envelope.

When using this Verification Method, the DTS Provisions are not mandatory, but can still be used as guidelines.

Step 3 – Testing.

Firstly, prepare the house for testing.

Close all windows, doors, trapdoors, and ventilation and other openings.

Blower door testing experts will then mount a blower door assembly at a door in the building envelope, and connect pressure measuring devices to the inside and outside of the house.

Step 4 – Assess compliance.

Compliance is checked using air permeability at a 50 Pascal pressure difference.

Air permeability is measured in cubic meters per hour per metre squared.

To achieve compliance, the measured air permeability must be no more than 10. When applied to homes, this is broadly equivalent to 10 air changes per hour.

If compliance is not achieved, remediation is required. Check all seals and possibly adjust as needed – then re-test.

Step 5 – Document results.

The test results should be clearly documented in a test report, confirming the procedure was in compliance with the relevant standard.

This Verification Method is clearly outlined, with worked examples, in the handbook: Energy Efficiency NCC Volume Two.

The handbook and other resources are available from the ABCB website.