Can the stars align? Investigating what it might take to achieve a seven-star energy rating for a timber-framed home

From 2022, the Australian government will introduce a minimum seven-star thermal energy efficiency rating requirement for new homes under the National Construction Code. With the timber systems currently being used, this will present some challenges.

To ensure our industry is best placed to meet these challenges, FWPA has engaged researchers at the University of Melbourne to explore what a seven-star rating might mean for timber-framed homes. They will also consider the options for how this can most realistically and cost-effectively be achieved.

FWPA Research and Development Manager, Dr Chris Lafferty said

the new requirement may be difficult for current timber systems to comply with, particularly in colder climates.

“Builders may have to rethink their practices and give extra consideration to the thermal detailing of timber frames in order to meet the new requirement,” Lafferty said.

Minimum energy efficiency standards were introduced in Australia more than a decade ago, as part of a push to reduce carbon emissions. A five-star regulation was introduced initially and increased to six-stars a few years later.

When the standard was introduced the CSIRO created an online assessment engine, on behalf of the government, which makes assumptions and considers various factors, before calculating an official thermal efficiency rating. The factors considered range from climate zone, to property orientation, insulation, windows and the materials used in the building envelope.

The initial stages of the research project will involve consultation with the CSIRO about the underlying assumptions of the software, to help build an understanding of current modelling limitations and the need for improvements.

This will be followed by an assessment of the framing, detailing and finishing options for creating a seven-star thermally efficient home.

Timber properties of various sizes and in different locations and climates will be modelled, with factors including double glazing, high performance glass, 120 mm thick walls, higher-performing insulation and a variety of cladding solutions all being considered. From this, the team will seek to determine the impacts of the different variables and the combinations that would allow a seven-star rating to be achieved most cost-effectively.

Dr Alastair Woodard, FWPA National Residential Construction and Fit-out Program Manager said the government still has some work to do in determining exactly what a seven-star rated building might look like.

“It will definitely have an impact on the building envelope, and might include new considerations such as the efficiency of appliances within the home, or the potential to create energy onsite through renewables,” Woodard explained.

Dr Woodard advised a series of different combinations of the measures needed to achieve both seven-star and eight-star efficiency in lightweight timber-framed homes will be developed. These recommended approaches will be shared with both the CSIRO and Housing Industry Association (HIA).

It is hoped the HIA will use the recommendations as a tool to help its members understand the impact of new requirement and how to achieve the best results.

“With further performance requirements scheduled for introduction beyond the seven-star energy efficiency rating, it’s crucial that we provide industry with knowledge and insights around the impacts, so they can best engage with the changes,” Lafferty concluded.