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How builders can benefit from better ratings on windows

Australian fenestration suppliers are missing out on millions of dollars worth of contracts because they are not getting the right results in terms of assessing U values for windows, according to the founder of Advanced Fenestration Research and Certification Lab, David Morehouse.

Mr Morehouse earlier this year started a business to address the problem that faces tier two builders and their suppliers in obtaining project specific data.

The drive for better thermal performance means more builders are looking for window manufacturers and suppliers to supply products with lower U values. But, most companies have no idea how to achieve them, Morehouse says.

There are two paths to achieving compliance under the National Construction Code for Section J energy performance requirements.

One is using the Windows Energy Rating Scheme (WERS), generally used for the Deemed-to-Satisfy approach. It is also a standard performance metric for most Australian manufacturers and suppliers.

“WERS is a fantastic apples versus apples comparison tool,” Morehouse says.

The performance pathway, however, requires the U values to be modelled more accurately. WERS is also not appropriate for custom-sized and custom-configured fenestrations.

Using WERS for this calculation, however, does not give more accurate result because the data behind the system is based on a set of AFRC standard window sizes and configurations that can be very different to what is actually being installed.

That means WERS modelling can possibly result in a worse U value being obtained than will actually be the case, as the window sizes may be smaller than what is actually going into the building.

Two software packages developed by Lawrence Berkeley are AFRC approved and used for simulating services:

  • Therm for simulating frame and glass sections, such as head, sill and mullions
  • Window for creating the whole of window U values (Uw), Solar Heat Gain Co-efficient (SHGC) and whole of window Visible Light Transmission (Tvw).

The company’s approach is to follow all of the rules and protocols of the Australian Fenestration Rating Council with exception to the rules relating to standardised sizes and configurations.

“We believe that simulations should include all of the components that are being supplied and installed by the window company and that were including in physical testing.

“This ensures that the consumer is getting results that represent the products that are being supplied.”

As well as helping suppliers and manufacturers give their products the exact simulated U value, SHGC and Tvw, the company also works with engineers consulting on projects.

In some cases simulations show that it is possible to obtain a required high performance level by upgrading framing while using a clearer, potentially more cost effective glazing system, especially in cooler climates where SHGC or Tvw requirements are higher.

“Sometimes you can get a better outcome in terms of performance without increasing the cost,” Morehouse says.

WERS is good for housing

“WERS is good for housing, and for people who need to compare similar products,” Morehouse says.

The big ticket opportunities for the fenestration industry, however, are the commercial projects, including offices, multi-storey residential, schools, hospitals and government buildings.

The next stage for the company is to start providing services around acoustic properties in fenestration.

A process is currently being developed that will enable it to provide the same level of results as standard lab testing at a fraction of the time and cost.

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