Renovating a house

If you're renovating your home, the things you can't see - like warmth, comfort and dryness - are just as important as what it looks like. Do it once and do it right, and you'll enjoy the benefits well into the future.

Making your renovation energy efficient can have big impacts on your power energy bills too. For example, an uninsulated home with electric heaters can cost 20 times as much to heat as a fully insulated home with efficient heat pumps.

It's worth paying a little more while you're renovating to get greater comfort and lower running costs for years - or even decades - to come.

When renovating, you need to consider:

insulation

blocking draughts for air-tightness

fixing dampness issues

double-glazing

space heating

thermal mass

hot water, lighting and appliances.

All building work, including renovations, needs to comply with the Building Code. You can find more information on the Department of Building and Housing's website, or by contacting your local council.

Bump up your insulation

Insulation is a fundamental part of making a home warmer, drier and healthier.

  • Get your ceiling and underfloor insulation up to a good standard first. Nearly 60% of homes don't have adequate insulation, so it pays to check - find out how to check your insulation.
  • The next step is to insulate the walls. To do this, take the wall lining or cladding off, install insulation and re-line the walls.
  • If you have recessed downlights, consider replacing them with non-recessed light fittings. They require holes to be cut in your insulation for fire safety reasons, which creates heat loss. Find out more about ceiling insulation and downlights.

Find out more about insulation.

Make your home more air-tight

Older houses often leak a lot of air, which means heat can easily escape. Problem areas include:

  • unused chimneys
  • holes cut in walls, floors and ceilings for plumbing, wiring or recessed downlights
  • cracks between floor boards
  • broken windows
  • badly-fitted windows and doors
  • walls cavities that are open to under the floor and into the ceiling space (air can flow through them) and have electricity sockets and switches in them.

A good start is to:

  • close gaps
  • block unused chimneys
  • seal obvious holes and gaps with sealant and expanding foam
  • put seal strips on doors and windows
  • replace recessed downlights with non-recessed light fittings.

If you are doing very extensive renovations you could also consider installing air-tightness membranes. These have recently become available in New Zealand at some hardware stores - they should be able to advise you on the best solution for your circumstances.

Fix dampness issues

Fixing dampness, mould, mildew and musty smells isn't hard when you renovate - here are some of the things to look for.

  • Put good externally-vented extractor fans in wet, steamy areas of the home - such as kitchens, laundries and bathrooms.
  • Don't vent into the ceiling space - it's bad for your house and your health, and it is not compliant with the Building Code.
  • Check for rising damp under the house. Check that all the vents are open and consider putting down a ground vapour barrier.
  • Avoid unflued gas heaters - they release a lot of moisture.

Find out more about fixing dampness.

Consider double-glazing

Replacing old windows with double-glazed units can halve window heat loss. Double glazing also reduces condensation and can reduce the amount of outside noise coming into the house.

Some double glazing is more effective than others - look for windows with frames that have insulating properties (like wood, PVC or thermally-broken aluminium), low-emissivity glass and an inert gas filling between the glass layers.

Find out more about double-glazing.

Get a good heating system

Once you have draughts, dampness and insulation under control, the next step is to think about space heating. Find out more about different types of heating and cooling.

Add thermal mass

If you have a house with windows that face north and rooms that get good direct sunlight, adding or exposing existing thermal mass will make better use of the free heat from the sun.

  • If you have concrete under your floors, consider exposing the concrete (you can polish or paint it) where it get direct sun. The concrete will absorb heat during the day and release it slowly at night.
  • Thermal mass can be added to wooden floors by pouring 50mm or more of concrete on top of the wood. Check with a buider to see if your floors are suitable for this option.
  • Don't forget that any thermal mass needs to be exposed to work properly. That means not covering it with carpets, rugs or any other type of insulation.
  • To maximise the benefit you get from thermal mass, if you can, insulate the outside of the mass. For example underneath a wooden floor that has a layer of concrete on it, or the outside of a brick or concrete wall that gets direct sun inside the room. 

Efficient hot water, lighting and appliances

The systems you use in your home can have a big impact on your home's running costs and environmental impacts. Find out more about:

Building and renovating tool

Use our online tool to find out areas where you can make energy efficient choices tailored to your building or renovating project.

 

More information

 

From the Resource Centre

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