How to prevent summer heat gain

Reducing the amount of heat that enters your home during summer will help you reduce the cost of air conditioning and keep your home more comfortable. Your home's walls, windows, doors, and ceilings work to insulate its interior living space, so the energy efficiency of those components can impact your cooling and heating costs.

Here are several things you can do to reduce heat gain in your home:


Graphic showing sources of heat gain: 48% of heat gain comes in through the windows.

Windows account for almost half of your home's heat gain in the summer.

  • Shade all sun-struck windows with shade screens, awnings, trees and shrubs on the outside, and window tints or film, blinds, shutters or drapery on the inside. Shaded windows can save up to 25% of the cost of air conditioning, when compared to unshaded windows.
  • Compare the ratings of window coverings before buying. The effectiveness of a window covering is measured by its shading coefficient. The lower the shading coefficient, the more effective the material is at blocking the sun.
  • Close draperies and blinds on summer days to help keep out the heat.

Walls and doors

Graphic showing sources of heat gain: 19% of heat gain comes in through walls and doors.
  • Paint exterior walls a light color. It will help reflect the sun and prevent your home from absorb as much heat, thereby keeping it more comfortable inside.


Insulation provides a line of defense between attic temperatures and the comfort of your living space. The effectiveness of an insulation material is measured in R-values and typically, the higher the R-value, the more effective the material is at reducing heat transfer.

  • Maintain minimum insulation levels of R-19 for exterior walls (total wall system) and R-30 in your ceiling.

Internal heat sources

Graphic showing sources of heat gain: 14% of heat gain is given off by internal heat sources.

Internal heat is the heat given off by incandescent lights, appliance motors, television screens, cooktops, washers and dryers, and even our bodies.

  • Avoid activities that can add excessive heat to your home during the hottest part of the day, such as cooking, doing laundry or running the dishwasher.


Graphic showing sources of heat gain: 13% of heat gain comes in through areas that are not well weatherized.
  • Inspect weather stripping around exterior doors and windows to ensure cracks are sealed and air isn't leaking into your home.
  • Caulk around window frames and all exterior wall penetrations such as pipes, electrical boxes, and vents.
  • Install foam or rubber receptacle gaskets on all switches and outlets.
  • Keep windows and doors shut tightly to retain cooled air.
  • Check pet doors to make sure they are snug and replace the rubber gaskets as they become worn.
  • Check the fireplace damper to make sure it's closed and that no daylight can be seen around the edges.


Graphic showing sources of heat gain: 6% of heat gain comes in through the ceiling.

Attic ventilation and insulation affect the amount of heat that is transferred from your attic through your ceiling and into your living space.

  • Make sure your attic is properly ventilated. Without proper ventilation, attic temperatures can reach 140-160 degrees. Such high temperatures not only increase air-conditioning costs, but also can reduce the life of your roofing material.
  • Check that attic exhaust vents are not blocked. Before installing an electric attic fan, calculate whether its motor won't use more electricity than it saves.

DIY projects to prevent summer heat gain

The videos on this page demonstrate various energy-saving projects you can easily do yourself to reduce the amount of heat that enters your home during the summer. Click the menu on the video to see other demonstrations in the series.