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H1 Calculation method tool

This tool checks for compliance of housing and small buildings with the calculation method of H1/AS1 5th edition amendment 1. Inputs are added on separate sheets and a results page is automatically generated, which can be submitted for compliance.

To input data and generate results on one sheet only, see H1 calculation method tool [basic].

Please read the instructions before using the tool.

Compliance requirements for H1/AS1 5th edition amendment 1

The use of H1/AS1 5th edition amendment 1 is restricted to housing, or buildings other than housing that are less than 300 m².

Buildings with curtain walling are excluded.

New methods for determining the thermal resistance and construction R-value of building elements are contained within H1/AS1 5th edition amendment 1 and include methods to calculate the R-values for slab-on-ground floors, windows, doors and skylights.

NZS 4218:2009 is no longer referenced within H1/AS1 5th edition amendment 1. Other standards have been added.

The climate zone maps have been revised to include six climate zones.

The window area of the building can be no greater than 40% of the total wall area.

The minimum R-value for a floor, wall or roof using the calculation method is 50% of the schedule method R-value for that building element. There is no minimum for doors and windows using the calculation method.

Where heating is embedded in a building element, a higher minimum R-value is required. See H1/AS1 5th edition amendment 1 for details.

Please refer to H1/AS1 5th edition amendment 1 for full compliance information.

This tool can not be used for H1/AS2 1st edition, which deals with larger non-residential buildings that have different requirements.

Using the tool

Select the climate zone and accurately enter all area and construction R-values for each building element.

Data should only be entered into areas that are shaded in blue.

Cells that are shaded in dark blue provide a dropdown list of options. Only options from the dropdown list can be used.

Calculated cells are shown in orange and cannot be selected.

This tool performs a number of checks and calculations and pass/fail compliance determined if appropriate.

This tool will not allow R-values to be entered that are below the minimum permissible for that element/climate.

This tool will also not allow unrealistically high R-values to be entered to reduce the likelihood of data entry errors.

The print area has been set to cover the white area on the Results sheet.

All the entered data will appear on the Results sheet so a printout of that sheet will contain all the necessary information.

The printout will list all of the individual building elements over a number of pages. The output should be scaled to 1 page wide.

Measurement of areas

Refer to H1/AS1 5th edition amendment 1 for definitions of building element areas and how to measure them.

Construction R-values

The designer must input construction R-values for the building elements. These are NOT the same as the insulation R-values.

Separate verification of the construction R-value should be included with your consent documentation.

Use the BRANZ House Insulation Guide 6th edition to find construction R-values or use the appropriate methods to calculate the construction R-values::

  • For walls, roofs and floors other than slab-on-ground floors, use NZS 4214
  • For windows, doors and skylights, see Appendix E in H1/AS1 5th edition amendment 1
  • For slab-on-ground floors, see Appendix F in H1/AS1 5th edition amendment 1

Interpretation of H1/AS1 5th edition amendment 1

This tool is implemented according to an interpretation of H1/AS1 5th edition amendment 1.

Limitations and liability

BRANZ Ltd accepts no liability for loss or damages resulting from use of this tool.

The accuracy of the calculation relies on the designer entering accurate values.

Restrictions on use

This tool is only to be used in its full, unmodified form.