Tag: NatHERS

Window-to-Wall Ratio

The ideal percentage of glazing to wall—often referred to as the window-to-wall ratio (WWR)—depends on several factors, including the building’s orientation, climate, and intended use. Here’s a general guideline for different orientations:

North-Facing Walls:

  • Ideal WWR: 20-40%
  • Reason: North-facing windows (in the Southern Hemisphere) receive the most consistent and beneficial solar gain throughout the year. A higher glazing percentage can optimize passive solar heating and daylighting, which can enhance energy efficiency and comfort.

South-Facing Walls:

  • Ideal WWR: 10-20%
  • Reason: South-facing windows receive less direct solar gain, especially in winter. Limiting glazing helps to reduce heat loss and prevent excessive cooling loads. However, strategic placement of high-performance windows can still contribute to daylighting without compromising energy efficiency.

East-Facing Walls:

  • Ideal WWR: 10-25%
  • Reason: East-facing windows benefit from morning sun, which can be useful for passive solar heating in the morning but can also cause overheating in the summer. Balancing glazing with shading devices is important to manage heat gain and glare.

West-Facing Walls:

  • Ideal WWR: 10-25%
  • Reason: West-facing windows receive strong afternoon sunlight, which can lead to overheating and glare issues. It’s crucial to use shading devices or limit glazing to manage these effects effectively.

General Considerations:

  • Climate: In colder climates, a higher WWR can improve passive solar heating. In hotter climates, a lower WWR helps reduce cooling loads.
  • Shading and Glazing Performance: The use of high-performance glazing and shading devices can allow for a higher WWR while managing solar gains and heat loss more effectively.
  • Building Use: The intended use of the building (e.g., residential, commercial, or office) can influence the optimal WWR based on factors like lighting needs and privacy.

These percentages are starting points and should be adapted based on specific design requirements, local climate conditions, and performance goals. Energy modeling and consulting with building professionals can provide more tailored recommendations for achieving the best balance of daylighting, thermal performance, and energy efficiency.

NCC 2022 State Extensions

In addition to our post on Victoria‘s decision to extend the implementation of NCC 2022 Energy Efficiency provisions to 1 May 2024, other states have also announced date extensions. Here’s the current run down:

New South Wales – new homes contracted before 1st October 2023 are exempt from the new sustainable building (BASIX) standards until 30 June 2024. Read more.

Australian Capital Territory – NCC 2022 has been delayed from 1 October 2023 and will now come into effect on 15 January 2024. Read more.

Queensland – The Residential energy efficiency standards will commence on 1 May 2024 through the updated Queensland Development Code Mandatory Part 4.1 – Sustainable buildings (QDC 4.1). Read more.

Here is a link to our presentation on the NCC 2022 Energy Efficiency provisions.

NCC 2022 Release

The much-anticipated National Construction Code (NCC) 2022 rule changes have been approved by Building Ministers. NCC 2022 is scheduled to be published on the 1st October 2022, with an expectation that States and Territories will adopt the new rules from 1 May 2023, with transition periods for new livable housing requirements, new energy efficiency and condensation mitigation requirements from 1 October 2023; and new low lead in plumbing product requirements from 1 September 2025.

As Thermal and Sustainable Design assessors the lifting of the Nationwide House Energy Rating Scheme (NatHERS) from 6-star to 7-star and the introduction of Whole of Home assessment are significant changes that we have been preparing our clients for.

Under the current 6-star requirement, R6.0 bulk insulation to the ceiling of the roof space and R2.5 wall insulation has been standard practical low-cost specifications for achieving certification. In most cases, this will not be enough to meet the coming 7-star rating. An insulated slab and Low-E thermally broken double glazing can bridge the gap but will increase the cost of the project. It’s important to consult with an Accredited Thermal Assessor early in the concept design stage of your project for assistance in improving thermal performance through passive solar design. Some simple design measures can have a big impact – see our blog for further information here.

The Whole of Home assessment is a completely new element to NatHERS certification, adding the energy efficiency of major appliances to the assessment, along with carbon offset measures.

Under NCC 2022 you will be required to select the type and energy efficiency rating of heating, cooling, cooking, lighting, hot water appliances, pool pumps, and pool heating that is to be installed. With an understanding of the complete energy use of the building your accredited thermal assessor will work with you to understand the measures required for the building to be carbon neutral. We see that this will initially include the installation of a suitably sized Solar PV system, though will expand as new technology such as battery storage reduce in price.

Here is a link to the new design of the coming NatHERS certificate, where you can familiarise yourself with how the NatHERS energy rating and new Whole of Home rating will be presented.

Feel free to get in touch to discuss NCC 2022 and what it means for your next building projects to comply with the NCC 2022 energy efficiency provisions.

Contact us for more information