3.8. Topic 16: The schedule method does not adequately limit heat losses and gains from skylights in large buildings
Proposed amendments to Acceptable Solution H1/AS2 Energy Efficiency for buildings greater than 300m2 to limit the permitted area of skylights in the schedule method to 1.5% of the roof area.
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3.8.1. Reasons for the change
Skylights are one of the weakest parts of a building’s thermal envelope. On a per square metre basis, heat losses and gains through skylights are significantly greater than through other parts of the roof.
Currently the schedule method does not limit the area of skylights in large buildings, allowing buildings to have large areas of their roof covered with skylights that can contribute to significant heat losses and gains, poor energy efficiency and thermal discomfort for occupants.
The proposal to remove the schedule method from Acceptable Solution H1/AS2 discussed in subsection 3.3 above would resolve this issue. However, depending on the feedback on this consultation, MBIE could decide not to proceed with that proposal.
3.8.2. Proposed change
The proposed change involves amendments to Acceptable Solution H1/AS2 Energy Efficiency for buildings greater than 300m2 to limit the permitted area of skylights in the schedule method to 1.5% of the roof area. This proposal is only relevant if MBIE’s other proposal to remove the schedule method discussed in subsection 3.3 above does not proceed.
3.8.3. Analysis of the proposed change
The primary objective of the proposed change is to support consistency and provide certainty for designers, Building Consent Authorities and building users that buildings have sufficient insulation for achieving Objective H1.1 of the Building Code, Functional requirement H1.2(a) and Performance H1.3.1(a).
For this issue, MBIE considers that the proposed changes will best achieve this objective in case the proposal to remove the schedule method does not proceed.
MBIE expects that the impacts of this proposal include:
- Lower energy usage (running costs and carbon emissions) from improved energy efficiency
- Better consistency of compliance
- More work for designers and Building Consent Authorities when establishing compliance. For buildings with skylight areas above the proposed limit, designers would need to use the calculation or modelling method instead.
On balance, MBIE considers that the benefits of the proposed change outweigh the costs.
3.8.4. Questions for consultation Topic 16
16-1. Do you support amending Acceptable Solution H1/AS2 to introduce a limit on the skylight area in the schedule method in H1/AS2 (in case MBIE does not proceed with the proposed removal of the schedule method from H1/AS2)?
- Yes, I support it.
- Yes, with changes.
- No, I don’t support it.
- Not sure/no preference.
16-2. Please explain your views.