Insulation & Glazing

New Zealand has a history of building poorly insulated and glazed homes. The good news is there are plenty of options for you to improve the heat retention of your home and workplace.

Insulation is essential to keep your home warm in winter and cool in summer, saving energy used for heating and cooling and reducing bills. Insulation also helps to reduce condensation, mould and mildew, and noise levels. Without adequate ceiling insulation, it’s estimated 42 percent of household heat is lost through the roof. Walls account for around 24 percent of heat loss and 10 percent of heat is lost through floors.

More than 75 percent of New Zealand homes have insufficient ceiling insulation and 70 percent of homes have no underfloor insulation where floor insulation can be installed. Add all that up and it’s easy to see why installing insulation makes sense!

The Building Code requires different minimum R values for insulation in ceilings, floors, walls, windows, and heated floors for Taranaki (Zone 2). Under the Building Code new homes and additions to existing homes must be insulated to meet or exceed minimum requirements. Ceiling and underfloor insulation is also required in all rental homes from 1 July 2019.

It's worth spending extra and exceeding the minimum requirements to ensure your home is as warm and comfortable as it can be, with the added bonus of lower power bills.

Learn more at the Smarter Homes website and in the detailed EnergyWise guides for ceiling insulation, underfloor insulation and wall insulation.

Find out if you apply for a Warmer Homes insulation grant here.

Local insulation installation companies:


Draught proofing

It’s important that once you’ve insulated your home, you reduce gaps, cracks and draughts around windows, doors and joints that will rob heat from your home and let in uncontrolled volumes of cold air. To find gaps and draughts:

  • Look for obvious gaps. Visible light under and around doors and windows is a good clue.

  • Listen for rattles or whistling, especially during strong winds.

  • Feel for moving air with your hand around doors, windows, fireplaces, air outlets, vents, stairways, floorboards, exposed rafters and beams, built-in heaters and air conditioners, architraves and skirting boards.

  • Look for movement in curtains.

Key locations and actions for draught sealing often include:

Chimneys - Your chimney can let a lot of air in and out of your home. So if you don’t use your open fire place, or in Spring and Summer, put a bag of stuffed newspaper up the chimney and cover the opening with a picture or hung rug. You can also install dampers at the top or throat of a chimney.

Under and around doors - All external doors should have a door sealer attached to the bottom - the screw on type are strongest. Note whether the door in question opens inwards or outwards, and the type of flooring it opens over (timber, carpet, tiles, etc.). There are also different products for internal doors, so make sure you choose the right product for each door.

Around windows - Stormguard V Seal or others are ideal at stopping air flow by filling the available gap. Always prepare the surfaces you are attaching seals to by ensuring they are clean and dry. Rubber or foam strips can also be used, but these will often need to be reapplied with glue over time.

Around walls and floors - Large gaps may require carpentry work to make the gaps smaller, or depending on size and location, could be filled with expandable fillers. A caulking gun can be used for smaller gaps. Silicone sealants should be used in areas exposed to the weather.

Around exhaust fans - While many exhaust fans have louvres that shut when the fan is turned off, if your fan doesn't self-close you can purchase a cover to place over your fan, or replace it (in time) with a self-closing fan.

Above halogen downlights - These need to be IC4 closed units, otherwise you create a little ‘chimney’ sucking air out, as these can’t have insulation over them for fire safety.

Local suppliers:

A lot of your home's heat can escape through windows, especially if you already have well insulated ceilings, floors and walls. Options for minimising this heat loss by providing insulation for your windows include:

If you don’t have curtains, these make a big difference to reducing heat loss, they’re not just aesthetic.  

  • Curtains need to be lined - this achieves a double glazing effect at a fraction of the cost. ‘Thermal backing’ on the back of curtains has a miniscule performance from a thermal perspective. To reduce heat loss you need a double layer to a curtain or blind, to trap air between the layers so it can warm. Buy second hand sheets or calico from Spotlight – anything without an open weave, the thicker the better. When you sew or pin the liner it to the top of the curtain it creates a layer of air between the curtain layers. If you can’t sew, you can even safety pin the second layer to the bottom of your curtain tape – that allows you to take it off and wash the lining. 

  • Ensure curtains run from the top of the window to the floor, with a bit of ‘puddling’ on the floor’ to stop draughts, given cold air will drop from the window and flow down.

  • Pull your curtains before the sun goes down to maintain internal heat and reduce heat loss.  

  • Pelmets are really important for stopping heat from being sucked down behind the curtain to make a draft. Or use a closed curtain track with a lid at the top. You can get these at Bunnings and Mitre10.  

Also see the Energy Wise guide for blinds.

Curtains & blinds

Double glazing, secondary glazing & DIY double glazing

Double glazed windows are really effective at holding in heat due to the insulating gas layer - either normal air or special heavy gases - held between the two panes of glass. Learn more on the Energy Wise website.

If you’re not able to install new double glazed windows, secondary glazing may be an option. See the Energy Wise checklist to learn more.

If you can’t afford new or retrofitted double glazed windows you can make a simple and very cheap double glazing effect for windows by applying bubble wrap to your windows. This is great for windows you don’t open often, and can easily be taken off in Summer. Cut to size, spray with water on the back flat side to help it stick to window, and apply. You can tape around the edges if needed.

A Window Insulation Kit is another way to achieve a cheap double glazing effect, with less visual impact. Use their double sided tape that’s provided, not regular double sided tape, which is not sticky enough and will yellow. Measure the window, and give yourself a bit of room on the edges. Clean and dry the surface. You may need to sand wood if paint is flaky. Stick double sided tape along the edges of the inside frame – not onto the window itself. Start from the top in sticking the film to the tape, pulling it tight. You can lift off pieces to pull tighter if needed. Then place a warm hair drier over the plastic to tighten it.

Watch a DIY video here on the Energy Wise website. Don’t let anything pierce the surface or that will compromise your double glazing effect!

Local retrofit double glazers:

Local suppliers of retrofit double glazing and DIY kits:

If you know of other stockists/retailers/suppliers/services or all round fantastic sustainable sources please let us know so that we can include them here.