Building for 7 stars doesn’t have to be costly or complicated. Simple design features and material choices make a big difference to energy efficiency and a home’s energy rating.
As we move towards the introduction of 7 stars under the Nationwide House Energy Rating Scheme, NatHERS expert Dave Rochford has some top tips and advice for builders, designers and assessors.
Home energy ratings made easy
NatHERS provides a flexible, adaptable option to meet the new National Construction Code (NCC) energy efficiency requirements. Currently around 90% of new home designs are assessed using the Scheme.
The increase to minimum standards for new homes will be introduced from 1 October 2023 in most states and territories. The expert advice is to begin with the basics.
“Building for 7 stars at its very foundation begins with good design and orientation. These two elements are absolutely crucial to reduce the costs in getting a home to 7 stars, and beyond.
“If you build for the local climate, allowing for shade and solar access as appropriate for tropical, temperate or cool climates, you will only need to make minimal changes to other building elements such as the width of eaves, and cross ventilation.
“There is plenty of good advice on positioning a house on the block. This makes a world of difference to the home’s thermal performance and its NatHERS rating.”
Dave adds, engaging a NatHERS assessor early on is also key.
“I would say the most important first step is to get a NatHERS assessor involved early in the design process. Accredited assessors, in particular, are extensively trained to improve ratings and provide options to get to 7 stars and beyond.
“If your client really cannot live without those massive western-facing windows, by working with an assessor early on, you can look at options to mitigate what I would describe as a less than ideal design choice. Maybe use better insulation, along with climate appropriate glazing or colours; the software is flexible and adaptable,” Dave added.
Windows, zoning and insulation
Double and triple glazing or coatings on windows is also worth considering to get some more stars on your NatHERS certificate. Costs have reduced considerably in recent years and there are thousands of options now available.
“NatHERS includes both default and custom window options. Generally, choosing defaults will usually result in a lower rating, so I would recommended switching to a custom window where all the specifications are known which allows for greater accuracy.
“And remember, windows need to suit the climate. Sizing, placement and shading (an absolute must if you have those massive west-facing fenestrations!) are also important considerations,” Dave said.
A relatively low cost option to get to 7 stars is to include more internal doors in the design, so mechanical heating and cooling estimates in NatHERS can be applied more accurately.
Doors can be included at the end of corridors, or at the bottom of stairs, or be situated near media and rumpus rooms that are only occasionally used.
Depending on the climate, ratings may also be improved by increasing the R value of wall, floor and ceiling insulation.
“Increasing your R value will make a big difference but you can also extend insulation to new areas for example underneath the slab, the garage and internal walls, especially to unconditioned zones, like laundries and bathrooms. However, you need to take care not increase condensation risk.
“NatHERS rewards homes with fewer ceiling penetrations with higher ratings. Consider whether your design can remove downlights that aren’t IC4 rated, roof windows and skylights and replace these with other lighting options that allow for continuous ceiling insulation,” Dave said.
Plan for fans, be cool with colours
Improvements to a NatHERS rating can also be achieved by adjusting the colour of the roof and the external walls, such as moving away from using darker roof colours in warmer climates. Even adjusting window frame colours can make a surprising difference.
Adding ceiling fans in all rooms will not only improve the NatHERS rating but the homeowners’ comfort.
“Many people don’t give much consideration to the colour of their roof, window frames and walls, but collectively these elements can make a big impact on a rating.
“Adding fans is also an easy win which will earn you NatHERS brownie points.
“This stuff really isn’t rocket science and it doesn’t need to be costly. By working early with an assessor, making good design choices and with careful consideration of materials and fittings, you will be on your way to 7 stars. It really is easier than you think,” Dave said.