Why is my home so hot in the summer?

There are many factors that can cause a home to get too hot in the summer, and many of them are energy efficiency issues:

• Insufficient attic insulation – in the summer, and on other hot days, radiant heat from the sun can permeate through your roof and heat up your attic like a solar heated oven. If you have insufficient insulation in your attic – the radiant heat will pass through the insulation into your living space causing the air inside your home to become warmer, and sometimes too hot.
• Inadequate attic ventilation – if there is insufficient attic ventilation, the temperature in the attic can build up due to heat that radiates into the attic. If the attic is under-insulated and/or if there is air leakage between your attic and living space the warm air from the attic will increase the temperature in your home.
• Insufficient wall insulation – if your south and west facing walls have high exposure to direct sun and are uninsulated or under insulated – the heat from the sun will pass through the walls and heat up your home.
• Air leakage – if there are gaps and cracks in your home (under doors, around windows, through attic penetrations, around your foundation, etc.) warm air will leak into your home increasing the temperature, and potentially the humidity levels, in your home.
• Inefficient windows – if you have many windows or large windows that have direct exposure to the sun (your home is facing south/west) and the windows are not energy efficient, heat can easily enter your home on hot days, causing high indoor temperatures.
• Insufficient ventilation within your home – especially in the summer, homes lacking proper ventilation (bathroom fan/range hood fan) can fill with stale air, and may feel stuffy and humid.

Energy efficiency solutions and behaviour changes that can help keep your home cool during the summer include:

• Attic insulation – ensure your attic is sufficiently insulated. The CleanBC Energy Coach Service recommends that homeowners strive to increase their attic insulation to R40 or R50 levels (if appropriate and recommended by a professional attic insulation contractor). Draftproofing should also be completed in your attic prior to adding insulation.
• Attic ventilation – if there is insufficient ventilation in your attic, have new air vents installed to meet current building codes ventilation requirements. When replacing roof shingles this is a good time to increase roof ventilation.
• Wall insulation – sufficient insulation in the walls will slow the movement of heat from the exterior of the home into the interior. Homeowners should work with a professional insulation contractor and have all walls fully insulated. If replacing the siding for your home this is a good opportunity to have insulation blown into the walls and/or added to the exterior of your home.
• Air leakage – draftproofing can be a cost effective strategy to keep your home cooler in the summer and warmer in the winter. See the FAQ, Where do I start to reduce drafts and improve my home?
• Windows – installing new, high-performance windows can act as a barrier between indoor and outdoor temperatures, keep the cool air in, and save you up to 8% on your energy bills. Talk to your window installer to help choose the best windows for the comfort of your home.
• Air conditioning – if air conditioning is required or desired, an air source heat pump is the most energy efficient and most climate friendly form of home heating and cooling currently available. See the FAQ, What are the benefits of mini-ductless air source heat pumps
• Heat recovery ventilators (HRV) – can improve indoor air quality by removing stale air and circulating clean, fresh air throughout the home.
• Using appliances less – minimizing the amount of heat you’re generating is a simple way to lower the temperature in your home. For example, on hot days plan for meals that do not require using the oven.
• Keeping the heat out – keeping the windows and blinds closed during peak hot hours of the day can help to block heat that enters your home through your windows. In the early morning and in the evening when it cools down, open your windows to let cool air in.
• Improving air flow – using a ceiling fan can lower indoor air temperatures by up to 10%. During the summer, set your ceiling fan to rotate counter-clockwise. When the air is cooler outside than it is inside (for example, in the early morning), you can also place a fan near a window to draw cool air into the home.
• Landscape for shade – planting the right size tree in the right place can block sunlight and help keep your home cool during the summer months. A deciduous tree will block heat in the summer and allow the heat to pass through in the winter, when the leaves have fallen. Trees planted on the east, west, and northwest sides of the home will provide afternoon shade.
• Install shading – exterior blinds or shades can block sunlight during the hottest times of the day, keeping the indoors cool.

Ask your energy advisor or contractor about which home energy improvements will be most effective for improving the energy efficiency of your home and maintaining a comfortable temperature all year round.

Did you see a building science or energy efficiency term you did not understand? Check out our glossary.