2.12. Topic 9: The look-up tables with R-values for slab-on-ground floors do not cater for some common situations

2.12.1. Reasons for the change

With all compliance pathways for the H1 energy efficiency insulation provisions, designers need to determine the thermal resistance (R-value) of the proposed building elements that form part of a building’s thermal envelope. For slab-on-ground floors, an easy way for designers is to look up the R-value of common types of slab construction from tables provided in Appendix F of Acceptable Solution H1/AS1. Calculating the R-value of a slab-on-ground floor requires specialist technical skills and software that most designers do not have.

Industry feedback and recent BRANZ analysis suggest that the current tables do not cover some common situations. This includes small slab-on-ground floors, and floors with slab edge insulation that does not go around the entire floor perimeter. For example, because of an attached garage.

This can make it difficult for designers and Building Consent Authorities to establish whether a building complies with the H1 energy efficiency insulation provisions. 

2.12.2. Proposed changes

The proposed changes involve amendments to Acceptable Solution H1/AS1 Energy Efficiency for all housing, and buildings up to 300m² to enable the use of the look-up tables for slab-on-ground floor R-values for more situations. Similar changes are proposed for Acceptable Solution H1/AS2 Energy Efficiency for buildings greater than 300m².

They include:

• Adding rows to the existing slab-on-ground floor R-value look-up tables in Appendix F of H1/AS1 for floors with area-to-perimeter ratios down to 0.6. Currently these tables only cover floors with area-to-perimeter ratios down to 1.6.
• Adding instruction for interpolating between different tables to enable determining the R-value of floors with slab edge insulation that does not go around the entire floor perimeter.

For more details of the proposed wording in H1/AS1, please refer to Appendix A.

Appendix A: Proposed changes to Acceptable Solution H1/AS1 [PDF, 4.4 MB]

2.12.3. Questions for the consultation Topic 9

9-1.  Do you support amending Acceptable Solution H1/AS1 as proposed to make it easier for designers and Building Consent Authorities to establish whether a building complies with the H1 energy efficiency insulation provisions by enabling the use of the look-up tables for slab-on-ground floor R-values for more situations?

• Yes, I support it.
• Yes, with changes.
• No, I don’t support it.
• Not sure/no preference.

9-2.  Please explain your views.

< 2.11. Topic 8: For some mixed-use buildings it is unclear whether H1/AS1 and H1/VM1 can be used, or H1/AS2 and H1/VM2 | 2.13. Topic 10: The look-up table with R-values for vertical windows and doors in housing misses some common glazing types >