NZ Building Code - Energy Efficiency

The thermal performance of a building (excluding assembly service, industrial, outbuildings and ancillary buildings) must satisfy Clause H1 Energy Efficiency of the New Zealand Building Code.

There are a number of routes for compliance with Clause H1.

Modelling method

Code compliance document H1/VM1 prescribes modelling as a method for verifying the compliance of all building types.

The modelling method in NZS 4218: 2004 Energy efficiency – housing and small building envelope is used for housing and small buildings (net area<300 m2).

The modelling method in NZS 4243.1: 2007 Energy efficiency – large buildings is used for large buildings (net area>300 m2). In both methods the performance of the proposed building has to be less than that of a prescribed reference building.

Building Performance Index (BPI) method

This method is limited to housing. The ALF3 model supplied by BRANZ is used to determine the BPI.

Schedule method

Compliance is verified for all building types by ensuring the R-values of walls, floors, roofs and glazing exceed the minimum R-values prescribed in code compliance document H1/AS1.

For housing, minimum R-values are prescribed for varying types of solid wood wall construction. These R-values account for the thermal mass of wood. This method is restricted to building with ‘modest’ areas of glazing.

Calculation method

This method is an extension of the schedule method. It allows R-values less than the prescribed minimums to be used for a building element(s) provided a higher R-value is used for other element(s).

The tradeoff may be limited by Clause E3 of the Code, which prescribes a minimum R-value for internal moisture control.