I am negotiating with an ESD Officer of a metropolitan Council and they are insisting on double glazing for a BESS assessment.
The client is hesitant to pay for another NatHERS rating and would just like an idea of how much of an improvement would be achieved?
There is on occasion crossover in the BESS assessment between building fabric energy performance and IEQ measurement. The IEQ pass mark gets a boost from ticking double-glazing.
This is regardless of whether the building fabric achieves a suitable level of performance at 6 Stars, or even 6 Stars plus 10% required by some municipalities, by applying good thermal design principles which may include single-glazing.
Double-glazing will usually deliver superior results but with the wrong glass can impact negatively by comparison to single-glazing for both thermal and acoustic performance.
Unconditionally demanding double-glazing could potentially cause in warranted housing affordability impacts and deliver inferior performance outcomes.
In some instances it might be prudent to run both scenarios to determine the outcome to advise the Client, then an informed decision can be made before cost implications of revised certificates are endured.