2.15. Summary of the proposals for housing and small buildings
Summary of proposals to change Acceptable Solution H1/AS1 and Verification Method H1/VM1.
TABLE 1-3: Summary of proposals to change Acceptable Solution H1/AS1 and Verification Method H1/VM1
| Outcome |
Potential changes |
| Optimising insulation to better balance upfront building costs and longer-term benefits |
- Remove the schedule method from Acceptable Solution H1/AS1, leaving the calculation method and modelling method as compliance pathways.
- Amend the minimum R-values in the calculation method to increase flexibility by:
- Reducing the minimum possible R-value for roofs in the calculation method from R3.3 to R2.6
- Removing the minimum possible R-value for slab-on-ground floors
- Harmonising the minimum R-value for other floors to R1.3 across all climate zones.
- Exempt buildings from the higher minimum R-values for heated building elements where embedded heating systems are solely used in bathrooms.
|
| Consistency and certainty of compliance and consenting |
- Clarify and update requirements for the modelling method by:
- Prescribing the use of the most recent weather files from NIWA
- Specifying the solar heat gain coefficient to be modelled for glazing in the reference building (proposed permitted range is no less than 0.55 and no more than 0.6)
- Reducing the natural ventilation setpoint for passive cooling from 24°C to 22°C for housing
- Adjusting default modelling assumptions for internal gains from electrical plug loads and occupants
- Adding a new requirement for modellers to document and justify any deviations from default assumptions.
- Require a framing fraction of no less than 38% to be assumed when determining the construction R-value of framed walls, unless a designer can demonstrate that a lower framing fraction is justified. Reduce the wall R-value in the reference building of the calculation and modelling methods from R2.0 to R1.6.
- Require the areas of roofs, walls and floors to be measured using overall internal dimensions.
- Modify the citation of NZS 4214 to calculate R-values.
- Clarify requirements for establishing which of the H1 acceptable solutions and verification methods apply for mixed-use buildings and exclude the area of building parts that are classified as housing, industrial or communal-residential when determining the area of the building.
- Amend H1/AS1 Table E.1.1.1 with construction R-values of selected windows and doors.
- Expand the slab-on-ground floor performance tables in H1/AS1 Appendix F to cover more situations.
- Remove references to the Annual Loss Factor (ALF) tool which has been withdrawn by BRANZ, and remove definitions associated with calculating the Building Performance Index (BPI) that were reliant on the ALF tool.
- Update references to the latest editions of the BRANZ House Insulation Guide, AS/NZS4859.1, and the Passive House Planning Package (PHPP).
- Make other minor editorial changes to improve clarity and readability.
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