Wall Insulation

The minimum thermal resistance (R-Value) of new wall building systems is R1.9 other than in the South Island and the Central Plateau whether climate conditions require an R-Value of 2.0

There are three main options for retrofitting wall insulation into existing homes. All these options for wall insulation retrofitting require a building consent due to the complexity of the work and the potential ramifications on the overall building envelope.

• Removing wall-board to fit insulation sections: The best, and slightly more expensive option, is to remove the wall board and fit building paper then sections of wall insulation to fully fill the wall cavity. Check our image gallery above for a handy EECA video guide to retro-fitting insulation easily, including the tip to leave a strip top and bottom to avoid the need to replace cornices or skirting boards.
• Foam wall insulation:This process involves drilling holes into the external (or sometimes internal) cladding of your home and injecting a foam - Urea Formaldehyde Foam Insulation (UFFI) into each individual wall cavity between the joists and nogs. The Building Research Association of NZ (BRANZ) has expressed concerns about shrinkage, cracking, missed sections and the installed thermal performance of foam wall insulation (refer Build Magazine article). There are also some concerns and uncertainty regarding the effect of the foam encasing electrical wiring.
• Blown fibre wall insulation: This process again requires multiple holes to be drilled into your wall to blow loose fibre insulation into each small wall cavity. The challenge with blown fibre is that it has a tendency to settle over time creating significant gaps in the wall insulation that heat readily flows through. For this reason and again the need to drill holes into each joist/nog cavity Smart Energy Solutions does not offer blown fibre wall insulation.

Smart Energy Solutions does not retrofit wall insulation unless it is a major consented renovation where you are removing or replacing the wall board.

Injected insulation foams or blown-in loose insulation requires holes to be made into each individual wall cavity to inject/blow-in the insulation. A single wall may have 9 - 16 or more individual cavities.

The risks come if the hole is drilled from the outside as watertightness may be compromised. The Energywise website states "it creates a higher risk to the weathertightness of the cladding and damages the wall underlay".

Injecting from the inside creates less risk but does require some redecoration to cover the drill holes.

• Thermal curtains: Heat will flow through the weakest part of your wall system which will always be the windows if you haven't got effective thermal curtains. Make sure they are well fitted and touch the floor to limit air flow.
• Ventilation: If your issue is damp or mould then effective ventilation (either natural or mechanical) may have a greater effect than wall insulation. Read more about ventilation.
• Wall Covering: For an existing masonry/concrete block wall, you can add Mammoth wall covering to improve the situation. Mammoth wall covering is an acoustic solution with a low R-Value but for a concrete block wall it can reduce the radiant cold effect and improve the comfort of rooms. It is available in a choice of colours and is glued to the concrete wall.