The R-value of insulation product is the measurement of its thermal resistance – the higher the R-value, the higher the resistance to heat - making the home warm in winter and drier in summer.
Under the current NZ Building Code (NZBC), new homes must have insulation installed with the minimum R-value, that R-value is dependent on the area you live in. Aotearoa is divided into three climate zones and have specific R-values for each climate zone – see picture below:
If the existing insulation is not in reasonable condition, then the owner must replace it with insulation that meets the current R-values as shown in the picture above, otherwise, all existing insulation must still be in reasonable condition to meet the requirements. This means there should be no mould, dampness, damage or gaps.
Insulation must be installed in accordance with New Zealand Standard 4246:2016.
References:
Healthy homes insulation standard, https://www.tenancy.govt.nz/healthy-homes/insulation-standard/
House insulation requirements, https://www.building.govt.nz/building-code-compliance/h-energy-efficiency/h1-energy-efficiency/building-code-requirements-for-house-insulation/house-insulation-requirements/
What is an R-value? , https://www.pinkbatts.co.nz/homeowners/choosing-right-insulation/right-r-value/