Insulating your house is like wearing a winter jacket- it helps you keep the heat inside. This creates comfort and cuts down your heating costs. If you live in an old house, as we do, then you might ask: which part of the house loses how much heat? Renovators are often unsure as to where insulation is best put to save on heating costs.
If you are building a new property, all walls, roof, and the floor will be insulated as is the norm today. If you are renting out an older home then the property needs to be insulated in the roof cavity, stopping heat escaping as well as underfloor, stopping the cold coming inside your home. Where do our homes lose how much heat? According to BRANZ, this is where our houses lose heat.
The insulation value is measured by the R-Value. The R-Value describes the insulation material's ability to resist heat flow- meaning how good the material is in keeping the heat inside your home in winter and outside your home in summer. The higher the R-Value of your insulation material is, the better it performs.
The R-Values in NZ construction differ depending on the area of your home- here the early 2020 building standards we found on the MBIE website (1). We have taken the R-values for timber or steel frame, which is the vast majority in NZ.
North Island except Central Plateau: Roof 2.9; Walls 1.9; Floor 1.3; Heated Floor 1.9; Windows 0.26; Skylights 0.26
South Island and North Island Central Plateau: Roof 3.3; Walls 2.0; Floor 1.3; Heated Floor 1.9; Windows 0.26; Skylights 0.31
The highest R-Values for NZ construction as of 2019 are for the roof 3.3; for the walls 2.0 and for the floor 1.3 (1).
If you are a renovator, please check out Energywise as you might be eligible for a grant to insulate your homes at here:
Below, we checked out for you different options to insulate your home and stay warmer and more comfortable inside your building. In New Zealand it is now a regulation for all rental properties to have underfloor and roof insulation (2).
While the R-value is important, it is also important to note that the value given by manufacturers is also dependent on a few things: is the insulation dry? Wet insulation is like wearing wet clothing and does not insulate as well. In time in nearly all buildings moisture will pass through the insulation. Some insulation materials can lose in damp and drafty conditions up to 90% of their insulation value.
Does the insulation allow moisture to pass through? If you have materials that do not let moisture pass through, damage to your structural frame as well as loss of insulation efficiency can occur. Is the insulation fluffy or compressed? Insulation that is compressed has less efficiency that insulation that is installed with enough room. How thick is my insulation? As a general rule: if the insulation is installed with enough space and dry and the thicker it is the more insulation or R-value it has. Are there gaps around your structural frame, leaving parts exposed?
Please be aware that the standards set are minimum standards, they should not be a target but a minimal requirement. The better the insulation, the more you will save in heating. Aiming for minimum standard is like aiming for a minimum wage in your career. It does get you something, but will you be happy with it?
(1) Building Performance NZ, 'R-values for common construction types', NZ Ministry of Business, Innovation and Employment, November 2019
(2) Tenancy Services, 'Current insulation regulations', NZ Ministry of Business, Innovation and Employment, November 2019