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Cooling your home

In some areas of New Zealand, homes get so hot that people resort to active cooling systems like air conditioning. However, there are a range of things you can do to make your home cooler without adding much to your electricity bill.

Open your doors and windows

As long as you don't have a problem with overheating due to direct sunlight, good cross-ventilation can provide most of your summer cooling needs.

Create cross-draughts by opening doors and windows in different parts of your house and allowing the breeze to move through your home. Fit security latches so windows can be left partially open during the day but still provide security.

cross ventilation

Reduce overheating in rooms that get direct sun

  • adjustable external window shades such as blinds, awnings or louvres allow you to shade rooms in summer but let light and heat in at other times of the year. External shading is much more effective than internal shading as it blocks the sun's heat before it gets inside.
  • eaves (or roof overhangs) above north-facing windows can be designed to stop direct sunlight getting into your rooms at the height of summer but allow direct light in the rest of the year. Overhangs are ineffective against low-angled morning and afternoon sun from the east and west.
  • planting deciduous trees that shade the north and west sides of your home in summer but loose their leaves in winter. Trellises can be useful for growing annual plants that help shade windows in summer

Insulate your house

A well insulated house doesn't just stay warmer in winter, but is cooler in the summer months too.

Passive cooling

There are various types of passive cooling systems available. These make use of ceiling and roof vents or chimneys. They use the heat of the sun to draw hot air out of a house. These sorts of systems are more common in countries like Australia where cooling is more of a concern.

Ceiling and floor standing fans are relatively cheap to buy and install and cheaper to run than air conditioning. They're especially good if you only get a week or two of really hot days a year.

Active cooling

If you do need active cooling then there are ways to make sure your air conditioner or heat pump will cool effectively and as cheaply as possible.

  • Try using just the fan. Most heat pumps or air conditioners have a fan only setting and this can help create cross draughts in your home. Keep your windows open while using the fan-only mode.
  • Use the dehumidifying mode. If it is the humidity rather than the temperature that is the problem, this mode will help whilst using less electricity than the full cooling mode. Shut your doors and windows in the rooms you're dehumidifying while using the dehumidifying mode.
  • Only use cooling mode on really hot days when the other methods aren't enough. Shut all your doors and windows in the rooms you're cooling. It's best to just cool one room as this is what most heat pumps/air conditioners are sized for. Set the thermostat to around 22˚C. The room won't cool down any quicker if you set it lower, but you are likely to use more electricity by overcooling.
  • Avoid using auto settings. If you forget to switch the unit off it will start heating if the temperature drops below the thermostat setting.
  • Use the right size heat pump that will cool your house properly without having to work too hard. The same rules apply for cooling as for heating.


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