Newly constructed homes around Australia are now around 50 percent more airtight compared with those that were built a decade ago, new research has found.

And tested airtightness levels align closely with those assumed by the Nationwide House Energy Rating Scheme (NatHERS).

Published by the CSIRO and funded by the Department of Climate Change, Energy, the Environment and Water, the latest research involved testing of 233 apartments and detached houses that were constructed in the last four years across Melbourne, Sydney, Canberra, Brisbane and Adelaide.

During the tests, a blower door test was used to identify the rate or air leakage and to determine where leakages were occurring.

Compared with similar testing that was performed in 2015, the report found that the homes that were tested during the latest exercise are on average up to 50 percent more airtight.

The report also found that newly constructed Australian homes performed comparatively well with countries such as the United Kingdom.

However, leakages were still uncovered in most new homes.

Primarily speaking, these were found in bathroom fans, sliding doors and poor or missing door seals.

Across Australia, there has been considerable effort to improve the airtightness of newly constructed homes as part of efforts to improve household energy efficiency and thermal comfort.

Buildings which are constructed to be airtight are built in such a way as to minimise the unintended air movements that occur within a building. This helps to prevent outdoor air from entering the home and prevents indoor air from escaping.

Poor air tightness can cause draughts and can lead to higher energy bills to the tune of up to 20 percent, the researchers say.

Conversely, homes that are too airtight and which do not have an adequate level of controlled ventilation can lead to condensation, mould and health issues for residents such as headaches and nausea from higher carbon dioxide and monoxide levels.

Whilst leakages were found in most new homes, CSIRO Senior Experimental Scientist and project lead Michael Ambrose said that others – particularly apartments – were found to be extremely airtight.

If controlled ventilation is not included, Ambrose said that this could result in significant problems as referred to above.

“Fortunately, there are simple and affordable ways to rectify these issues and preventative measures that can be implemented during construction,” he said.

The report outlines a range of recommendations relating to building regulations in order to improve airtightness and ventilation performance.

These include:

• establishing air tightness standards in the National Construction Code (NCC)
• requiring controlled ventilation in new buildings, particularly apartments to reduce indoor pollutants and moisture
• mandating air barriers such as building wraps in all new residences; and
• providing on-site training and educational resources to connect builders with cost-effective solutions that improve building performance.

NatHERS a reliable indicator of Airtightness Performance

The study also found that actual tested levels of airtightness are closely aligned by those which are assumed under the Nationwide House Energy Rating Scheme (NatHERS), which provides an energy efficiency star rating for residential buildings.

This, Ambrose said, provided strong confidence that NatHERS is accurately predicting airtightness within specified levels and that as-built homes are in fact delivering the level of energy efficiency in practice which is suggested by the NatHERS rating.

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