The Best Underfloor Insulation for NZ Homes

Underfloor Insulation is an essential part of any home insulation project, and all rental properties in New Zealand with a raised and accessible under floor area, are now required to be insulated with thermal insulation. Floor insulation is installed under the house, between the floor joists. If you find that you’re unable to access part of the underfloor area, it’s important that you insulate whatever areas which can be safely accessed.

How Effective Is Underfloor Insulation?

Anyone who has lived through a New Zealand winter in an uninsulated house knows how incredibly cold the floor can get. Many people are lead to believe that this is due mainly to cracks or gaps in the flooring material itself, and hope that by lining the floor from the inside will fix the issue. This doesn’t work – even a thick carpet won’t properly address the underlying problem, since carpet in itself is not an effective insulator. When the outside temperature is colder than the indoor temperature, the cold is easily transferred through the timber floorboards, even if these are free from cracks or gaps. This is why no insulation means a cold floor in winter, even if you manage to heat up the rest of the room to a comfortable temperature.

Underfloor insulation works effectively by restricting (slowing down) the transfer of heat and cold between the outdoor and indoors. The insulation material itself contains millions of tiny air pockets, which is the secret behind all bulk thermal insulation. With underfloor insulation installed snugly between the floor joists underneath your house, you can warm up your home and the floor inside also gradually warm up to a comfortable temperature.

Underfloor Insulation Options in New Zealand

Even if we were not legally required to install under house insulation in New Zealand, it would still make a lot of sense to make this one off investment. In addition to the tangible comfort-factor, there are also energy costs to consider. When properly installed, underfloor insulation will noticeably reduce the energy required to maintain a comfortable indoor temperature, all year round.

People often ask “What kind of insulation should I use under my house?” There are a number of popular underfloor insulation options in New Zealand – two of the most popular ones are glasswool and polyester. Let’s take a closer look at these two options, and the brands under which they’re sold here in New Zealand.

Polyester Underfloor Insulation

Autex Greenstuf Polyester New Zealand logo

GreenStuf Underfloor Rolls

Autex Industries manufactures the hugely popular GreenStuf Insulation locally, and it’s the only polyester underfloor insulation we sell. The polyester underfloor rolls are totally itch-free and exceptionally pleasant to work with, and the only tool required to install this product is a commercial stapler, and a sharp knife.

Glasswool Underfloor Insulation

Earthwool Underfloor RollsBradford Gold Insulation New Zealand logo

There popular underfloor insulation rolls are made from low-itch glasswool, and lined on one side with a “wind-wash barrier”. This protective barrier serves two very important purposes.

  1. It protects the glasswool from the effects of the wind and weather, keeping the underfloor insulation both intact and looking extra presentable for the long term
  2. It enables the installer to easily fix the insulation in place using a strong stapler.

Pink Batts New Zealand logoPink Batts Snug Floor

These underfloor insulation Batts are also fairly easy to install, but require a bit more preparation and work to install. The individual batts are installed individually, and strapping is used to hold them in place for the long term. Pink Batts are a Fletchers Insulation brand, and are one of the most recognisable insulation products in New Zealand.

Check out this video showing how to install Pink Batts Underfloor Insulation.

Bradford Gold Insulation New Zealand logo

Optimo Underfloor Insulation

Optimo Underfloor is manufactured by CSR Bradford, and similar to the Pink Batts Snug Floor, come in individual rectangular segments. Bradford Optimo insulation segments are renowned for their stiffness, making them easy to “friction fit” in between the floor joists. They are also the only underfloor insulation brand available as high as R2.6, making them the underfloor insulation option of choice for home owners wanting the highest level of thermal comfort without the hassle of installing more than one layer of insulation.

Minimum R-Value Requirements for Underfloor Insulation in NZ

After 1st of July 2019, all rental properties in New Zealand with an exposed underfloor are required to be insulated with underfloor insulation in all accessible areas. There are a few narrow exceptions to this, for example if the house is soon to be demolished. Also, underfloor areas which are physically impossible to access are not required to be insulated, but all accessible areas do need to be insulated.

New Zealand is divided into 3 Climate zones, however the minimum underfloor insulation R-Value requirements across all of New Zealand is R1.3. Considering the long term benefits of underfloor insulation, we strongly recommend our customers to upgrade to a higher R-Value, as it’s more costly to upgrade the insulation later on.