NRG Green Board

Created by Vicki Marshall, Modified on Mon, 07 Nov 2022 at 12:22 PM by Vicki Marshall

Region: All States

Assessor Question:

Based on the thermal rating literature for Green Board, a 75mm board has an effective overall R value of 2.83 when installed on timber or steel frame wall.

When this wall type is modelled in FR5 with an effective overall R value of 2.83, the specific job I am working on rates well above 6 stars without the need for bulk insulation in any external walls.

My question is – is there as minimum requirement for bulk insulation in external walls or if a cladding system is efficient enough (as is the case here) can an assessor model to 6 stars without the need for bulk insulation in external walls?

TechLink Response:

NRG Greenboard is a SIPS product incorporating EPS as the insulation core. When applied to the outside of a framed wall it will provide a continuous insulation barrier which also eliminates the effects of thermal bridging through structural members.
If the builder ensures it is installed to comply with the requirements of the NCC and Australian Standards, namely:
- abuts or overlaps adjoining insulation; and
- forms a continuous barrier with ceilings, walls, bulkheads, floors or the like that inherently contribute to the thermal barrier; and
- does not affect the safe or effective operation of a service or fitting.

There might not be a need for insulation installed to the wall frame to reach a minimum regulatory compliance.

However, as the cost of insulation batts is not significant but the effects to long term thermal comfort and reduced greenhouse gas emissions are improved it is always encouraged to go beyond if possible. When adding the insulation values of the NRG Greenboard to your thermal model, ensure any stated R-values are not total system values and enter the product-only value, plus any relevant reflective or non-reflective air spaces.
NatHERS software can be used to demonstrate regulatory compliance as a Deemed-to-Satisfy option with NCC/BCA Part 3.12, providing the minimum star rating and heating/cooling limits comply.
Using this option means thee are no minimum insulation values which need to be adhered to, however again if the opportunity exists to improve on minimum it is encouraged to do so.