Underfloor Insulation

The thermal resistance value or R-Value required for underfloor insulation to meet the New Zealand Building Code is R-Value 1.3. This standard is the same for all geographic regions.

There is a range of underfloor insulation materials available each with their pros and cons.

• Polyester underfloor insulation sections: higher density sections that are easily squeezed in between joists and are self-supporting without staples or straps. Polyester insulation is moisture resistant.
• Polyester insulation blanket: can be stapled snugly into position by professional installers. Stapling underfloor where there are live wires can be dangerous for DIY installers.
• Fibreglass underfloor insulation: this material is low density and is used extensively in ceilings and floors but underfloor can be affected by the damp conditions.
• Foil underfloor insulation: was used extensively years ago for reducing radiant heat loss. It's effectiveness is lost when it is tarnished or corroded, collects dust or condensation, gets ripped or damaged. Due to risk of electrocution in working with a conductive material around electrical wiring - extreme care must be taken with installation. Installing foil insulation is not an accepted underfloor insulation option under the Residential Tenancies Act. 
• Polystyrene underfloor sheets: these are rigid sections that have been used extensively in the past. The polystyrene must be isolated from TPS wiring for safety as it can be affected by the polystyrene material. Some forms claim to be self supporting but require tacks or fittings to hold them in place.

If the ground underneath your home is regularly damp you should have a ground moisture barrier laid to avoid "rising damp" which can cause mould and unhealthy damp conditions in your home.

A ground moisture barrier is polythene sheeting which can be installed at the same time as your underfloor insulation. If your property is eligible for an EECA subsidy - it will cover this cost as well.

Foil insulation was commonly used underfloor in the past and it does provide insulation from radiant heat loss but does not have an R-Value like bulk insulation. Existing foil insulation is only effective for radiant heat loss if it is intact (not ripped) and is neither dusty or tarnished.  

If you do not already have underfloor insulation installed, foil insulation is not accepted as a solution under the Residential Tenancies Act.  

Typically our dedicated installation team need at least 40cm height between the ground and the bearer to safely install your insulation. The access point from outside must similarly have at least 40cm height clearance. Areas with less clearance or badly littered with broken glass or debris may not be able to be insulated.