On a hot summer day there is nothing better than having home air conditioning, but the costs of running your A/C all day can make a huge dent in your bank account. If you’ve ever wondered why your air conditioning doesn’t shut off even when your house seems cool, take a look at your roof.

When the sun is shining bright outside, your roof can be 10 degrees hotter than the ambient air temperature and contribute to up to a third of all heat build-up in your house, especially if you have conventional black roof tiling.

Most A/C units sit near the attic and must work constantly to remove the heat retained by the roof in order to keep your house at a comfortable, cool temperature. However, you needn’t bust your budget to keep your house cool, as there are many ways to cheaply and effectively prevent a hot house. Here are some ways for you to consider.


Ventilation is key to releasing heat trapped in your roof, and by installing ridge and soffit vents along the peak of your roof, at the tops of your sidewalls, and on the underside of your roof overhangs, you can cut the temperature by as much as 10 degrees. Ventilation works by moving air through your attic or roof space via natural convection, or forced air through a motor. Hot air naturally rises, so trapped heat will escape through vents, drawing up cooler air from below to absorb more heat to be vented out. A good ventilation system will also remove humidity in the home, thus preventing another problem: mould.

Radiant barriers

Installing a radiant-barrier roof can forestall much of the heat build-up in your roof by either reflecting most of the sun’s rays away or by not absorbing as much heat. Roofs that helps to keep your house cool in this way are also called “cool roofs”, and a cool-roof design can be as simple as choosing a lighter colour roof, as dark colours tend to absorb more heat.

While this can reduce the amount of heat build-up, there are other more effective methods, such as metal roofing or slate roofing. Metal roofing is light, relatively inexpensive, recyclable, long lived and very heat conductive, meaning it will not only reflect heat away from your home, but any heat it absorbs will also be quickly released into the atmosphere as the day gets cooler. Combining a metal roof with a good ventilation system will go a long way to keeping your house and your budget cool. Slate roofing is made from slate rock, which can be heavy, but is also a long-lived material that is waterproof and largely heatproof.

Recycling the heat trapped by your roof

An alternative way to keep your house cool and save money is to creatively recycle the heat absorbed by your roof. Through a system of pumps, pipes and vents, you can use the heat that is otherwise undesirable to heat up other parts of your home, such as your basement and your water.