All About the H1 Changes

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Top-Tier Thermal Modelling

There has been much discussion about the incoming changes to the Energy and Efficiency section of the New Zealand Building Code. 

With most centred on confusion about what these changes will mean in practice. 

H1 Changes for slabs on ground – What are the key changes?

  • No longer are foundations deemed to hold a minimum R-value of 1.3.
  • A foundation must be calculated on its area to perimeter (A/P) ratio to determine the floor’s R-value, this will assess the level of insulation required.
  • The H1 update has split New Zealand into six climate zones. For slabs on the ground, there are only three different minimum R-values. See maps below.
  • Soil conductivity has been raised from 1.2 to 2.0. 
  • R-values are no longer worked out on material R-values.
  • Thermal modelling of insulated products is now required to prove R-values.
  • The calculation method used now is completely different from what it was previously. As such any slab R-values prior to the November 2021 H1 release are not acceptable (ie BRANZ Home Insulation Guide 4th edition etc).

What does this mean practically?

  • Most foundations will require edge insulation at the very minimum.
  • Foundations with underfloor heating will require edge insulation and base insulation (thickness will be determined by its A/P ratio and climate zone).

Some examples of what this will look like in practice using QuickSet are below.

For floors with no embedded heating, the likely scenario will be:

  • If the ratio is low (1.00 – 2.50), the slab will require both edge insulation using QuickSet Taper plus 25mm base insulation unless it is brick cladding. Then it will require edge insulation using QuickSet Rebate and not require base insulation.
  • If it is a more favourable ratio (2.50 plus), the slab will require edge insulation using QuickSet Taper and not require base insulation.

For floors with embedded heating, the likely scenario will be:

  • If the ratio is low (1.00 – 2.50), the slab will require edge insulation using QuickSet Ultra and 75mm base insulation unless it is brick cladding.  
  • If it is a more favourable ratio (2.50 plus), the slab will require edge insulation using QuickSet Ultra and either 25mm, 50mm or 75mm base insulation, depending on the ratio.

The table below shows the minimum R-value’s across the climate zone’s.

How do I work out the area to perimeter ratio?

More to explore