Flooring insulation
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Energy savings
A recent survey indicates that over one million New Zealand homes have inadequate underfloor insulation. [1.]
Some floors such as ill-fitting tongue and groove planking have particularly high heat loss.
Types of products
In t he past the most common material used was a reflective foil which is stapled along the floor joists.
Reflective foils do not have an R value by themselves, but work in the following ways:
- they traps air between the floor and the foil which serves as insulation
- escaping heat is reflected back into the house
- it helps reduce the amount of moisture entering the house through the floor.
The performance of underfloor foil is very dependent on how well it is installed. Incorrect installation can significantly reduce it effectiveness.
As foil is metal based it conducts electricity and if the foil or staples used to fix it come in contact with live electric wires under the house, there is a serious risk of electrocution.
Given the safety risks and requirement for correct installation, EECA does not recommend the use of underfloor foil.
The other main type of underfloor insulation is bulk products such as polystyrene, wool, or polyester.
These products fit between the floor joists and either go hard against the underside of the floor or have a small gap between the bottom of the floor and the top of the product. In some cases the product are held in place by being slightly squashed between the floor joists and in other cases clips or other fixings are required.
Bulk products do have an R value, and are easier to install correctly than foil products. EECA recommends using bulk underfloor insulation, with a minimum insulation level of R1.4.
Dealing with dampness
Moisture can occur as a result of dampness underneath or around the edges of the house. This make rooms harder to heat.
Underfloor insulation can help reduce damp problems. However, if the area underneath your house is damp, then you should get it checked by a builder.
Although dehumidifiers help fix the symptoms of damp problems, better drainage and/or a moisture-proof groundsheet will fix the cause of the problem.
Take action
Keep safe when installing underfloor foil
It is essential that you keep staples well clear of any power cables when stapling underfloor thermal insulation.
Be sure to read the safe work practices Installing under floor thermal insulation – Electric shock hazard [Energy Safety website.]
Installation standard
Standards New Zealand has published a standard on installing insulation, NZS4246:2006.
- It covers a variety of products available and provides detailed instructions on how they should be installed and can be downloaded from here.
Seek professional advice
- Consult a builder or visit a hardware shop that sells insulation products.
- Use our Energy services directory: Find an expert.
- Get a professional report of your home’s insulation requirements with a Home energy rating assessment.
Understand product labelling
To find out more about the labelling on insulation products, go to the section About insulation: Product labelling.
Apply for an insulation grant
If you are on a landlord, low-income homeowner or tenant, find out if you will qualify for a home insulation grant.
More information
- For comprehensive information on insulation, download the Department of Building and Housing booklet Your guide to smarter insulation, PDF 2.9 MB [Smarter insulation booklet.]
- Insulation options [Smarter Homes website.]
Note:
[1.] New Zealand House Condition Survey, BRANZ, 2005.