H1 and higher R-value requirements

The implementation of the H1/AS1 5th Edition updates to the Building Code increases the minimum insulation (R-value) requirements for all new kiwi homes, with the goal of improving energy efficient to make them easier and cheaper to keep warm and dry.? A drier home also has health benefits, meaning fewer trips to the doctor.? Homes with improved thermal efficiency place less demand on our energy resources and infrastructure which helps reduce our carbon footprint (14% of a home owners annual energy usage will be for heating).

The new H1 calculation methodology for determining the R-value of construction products is quite different to the old one.? The most obvious part is the use of six distinct climate zones to replace the old three-zone system. This caters for regional winter temperature variations and insulation requirements better.

For housing with concrete foundations, the previous H1, 4th Edition regulations assumed all concrete slabs had a minimum R-value 1.3 which was the minimum requirement across all three old climate zones.?? Under the new H1 requirements, slab foundations must have minimum R-values from 1.5 to 1.7 (depending on the climate zone).? On the surface, this may not seem like much but because the calculation methodology has changed, they are more significant than they first appear.? The increases are much more pronounced for other flooring types (see table below). As an indication, a typical new single-level 156sqm/2-3brm kiwi home, with an Area/Perimeter ratio less than 3, will now need some form of edge or under slab insulation to achieve the minimum R-values.

The changes to H1 thermal requirements for key building products are as below:

R-values Explained

A material’s resistance to conductive heat is measured in terms of thermal resistance (R-value) between a warmer and colder surface, the higher this value, the greater the insulating qualities of a material. As a basic rule, increasing the amount of insulation in your home increases its R-value (proportionately) and because it is measure of heat flux between two surfaces it is relevant to both heating and cooling. ?The R-value of a product is relative to the density of the material(s) and its thickness. R-values can change with temperature and age or be impacted by things like settling or moisture content. R-values are also additive, so if two products are used together, their individual R-values can be totaled.?

Correct installation is critical for ensuring insulation products perform as per manufacturer's specifications, E.g. a compressed material will not provide its full R-value. The R-value of a material can be impacted by thermal bridging where the warmer and colder surfaces are connected by a more conductive material. Think wooden joists in timber floors or metal frames in older-style windows.

It is important to ensure products are installed correctly, made from quality, durable materials and, ideally, have proven thermal performance with independent thermal modelling.

Firth edge and perimeter under slab insulation solutions help engineers and architects achieve H1 compliance for new builds.? To see the R-value these products can achieve for your specific design go to our free and easy-to-use R-value Calculator at: https://www.firth.co.nz/r-value-calc/

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