Site Exposure

Exposed - the definitions have removed the phrase ‘Unit above 10 floor’ and added ‘without obstructions at a similar height to the building’ to a exposed high rise unit. 

Open - the definitions have removed the phrase ‘Medium-rise units above 3 floors’ and added ‘elevated units with a few obstructions of similar height to the building’. 

1. Could you please help me interpret the meaning of obstructions in the new definition?
2. What is the minimum distance to the neighbouring building to define it as an obstruction?
3. For example - For Exposed definition – what should be the minimum distance to the neighbouring building that we can safely consider ‘without obstructions at a similar height to the building’?

Similarly for Open – what is the meaning of few obstruction, i.e. – what should be the minimum distance to neighbouring building and density as a guide?

4. What is the amount/ number of neighbouring buildings considered (density) at the above defined minimum distance?

TechLink Response: 

• The current NatHERS Technical Note is the June 2019 version. This supersedes all earlier versions.
• The formal understanding is that the Technical Note nominally takes precedent over each of the four software product’s manuals.
• That said, it is appropriate for a TPA to exercise professional judgement where individual project attributes are not fully described in guidance publications.
• It is the responsibility of a TPA to be confident that the energy rating assessment that they prepare does not create an overly optimistic result.
• The critical consideration when selecting the exposure category is the likely wind pressures which will impact on cross ventilation and air leakage.
• As a result there are often swings and roundabouts with winter and summer performance.
• A lower level apartment in a tower in Southbank or CBD is likely to be impacted by wind tunnel effects.
• Accordingly it is probably prudent to choose “Exposed” for apartments below level 10 even if surrounding buildings are constructed to higher levels. 
• It is often wise to test a number of apartments in a building with the optional settings to gain an understanding of the difference it makes.
• This will provide the basis of substantiating a decision for the project as to which selection delivers the most realistic result.

4. Could you please confirm the discrepancy between the latest FirstRate5 manual (%.3.2a) and NatHERS tech note 2019 and please confirm if we should refer only to NatHERS technical note 2019 instead of FirstRate5 Manual Version 5.3.2a as the manual is still referring to NatHERS technical note version 2014?