Home insulation

One of the reasons many Kiwi homes are difficult and expensive to heat is that they’re poorly insulated. Insulating your home will not only make it nicer to live in, it should save you money in the long run. 

How it works

There’s not much use heating your home if the heat simply escapes through the roof, floor or windows. That’s a waste of energy and money.

New Zealand building standards require new homes to have insulation. But if your home was built before 2007 it may have insufficient insulation – or even none at all if it was built before 1978. 

Insulation could save you money and make your home warmer and more comfortable. Here’s the key areas to think about, the percentages below are sourced from the Eco Design Advisor website.

Floors and ceilings

In an uninsulated home up to 35% of heat escapes through the roof, and another 14% can sneak out the floor too. While heat is lost through walls too, insulating them usually requires opening them up so it’s more difficult. There are different types and grades of insulation and to work out how effective they are, check their R-value or thermal resistance rating. The higher the R-value, the better they are at keeping heat in. The building code sets out minimum R-values for new homes depending on where they are in New Zealand, but it’s worth getting the highest R-value you can afford. 


Up to 9% of heat can also escape through gaps around doors and windows too, which also create chilly draughts – but they’re relatively easy and inexpensive to fix. Tighten loose catches on windows and doors and seal gaps with weather seal, fit draught stoppers under doors and plug gaps in skirting boards etc. with sealant – your local hardware store will be able to advise on the best products to use.


Up to 31% of heat in uninsulated homes literally goes out the window. And in homes with good insulation elsewhere, single-glazed windows are the main source of heat loss. They also create condensation and ‘weeping windows’. The best way of insulating windows is to create a barrier of still air in front of them. There are different ways to achieve this, each with their own pros and cons and level of effectiveness, including:

  • Window films are the cheapest option which you can stick onto wooden window frames
  • Good quality curtains with a separate lining and blinds
  • Secondary glazing which requires installing a second pane of glass or an acrylic sheet behind your window
  • Double glazing – replacing existing windows with a sealed unit consisting of two panes of glass. You can also fill the space between panes with an inert gas to increase insulation effectiveness

Find out more about window insulation options at Gen Less.

How much it costs

Floor and ceiling insulation

It depends on the size of your home and the R-value of the insulation but as a rough guide, installing ceiling and floor insulation in an average three bedroom kiwi home can cost around $3,000 - $5,000.

Window insulation

The costs below are approximate and have been sourced from New Zealand Green Building Council:

  • Window film – around $30 for 1 or 2 windows
  • Double glazing – around $500-$600 per m2
  • Curtains with a separate lining or blinds – around $3,500 for an average three bedroom home

Good Energy Upgrades are just one step away


Ceiling and underfloor

Give ceiling and underfloor insulation a yearly check and replace any that may be damp or damaged. Ceiling insulation can settle and compress over time – a common guide is that if it’s less than 12cm it will need topping up. 


Double glazed windows: clean them just as you would ordinary windows. 

Insulating window film: they are designed to be replaced after one season, but can last several, however the tape may leave a mark if you remove it after more than one season. Clean them carefully with a soft cloth and window cleaner. 

Benefits — for you and the planet

Using renewable energy

Insulation helps reduce the energy required for heating – and the need to top up New Zealand’s renewable energy supply with electricity generated by burning fossil fuels like coal and gas.

Is it right for you?

It depends on your home including ease of access to ceiling and underfloor spaces, your budget, and the level of insulation you already have. 

It’s sometimes said that insulation is the most effective form of heating. If your home is poorly insulated, it will be hard to heat and to keep warm. That’s why it can make more sense to invest in insulation before you invest in upgrading your heating.

Warmer Kiwi Homes Programme

Depending on your situation you may be eligible for a Warmer Kiwi Homes grant from the government. Grants can cover:

  • 80-90% of the total cost of ceiling and underfloor insulation
  • Up to 80% of the cost of an approved heater (e.g. heat pump)

 Find out if you’re eligible for a Warmer Kiwi Homes grant.

How to get insulation in your home


HomeFit self-assessment is a straightforward way to check if a home is warm, dry, efficient and safe. You can use it to check a home you’re looking to buy or rent, or if you want to know how you can improve your current home. It starts with a simple online check.

If you would prefer to speak to someone you can contact an independent HomeFit assessor who can visit your home to provide a detailed assessment and list of priorities. 

HomeFit was developed by the New Zealand Green Building Council and is proudly supported by ANZ.

Important information

The material is information only and you should seek professional advice about your circumstances. While we’ve taken care to ensure the information is reliable, we don’t warrant its accuracy, completeness, or suitability for your intended use. To the extent the law allows, we don’t accept any responsibility or liability arising from your use or reliance on this information.