In the warm months, think of the ventilation provided by windows as your thermostat. You can open windows and close window coverings to maintain a comfortable temperature all day, indeed all summer long.
Replace inefficient windows
Multi-paned windows with a low U-factor for heat conductivity will not only retain heat in the winter but also help regulate temperature changes over the course of a warm summer day. The lower the U-factor, the better insulated the window is. Look for ENERGY STAR®-rated insulating windows.
Apply heat-reflecting film
Consider coating your south- and west-facing windows with a low-emissivity film to reflect heat while continuing to let in light.
Install windows that open
The thinking on building design has come full circle: windows that you can open to let in fresh air are now considered best for year-round comfort and energy savings.
Add window coverings
Between 40% and 65% of the heat entering your home on hot days comes in through windows. Make sure you have blinds or curtains on all windows exposed to direct sunlight to help keep it out.
Use fans, not air conditioning
Even the most efficient air conditioners use a lot of electricity. In parts of B.C., a portable or fixed ceiling fan will generally do the job of keeping a room cool while using about one-tenth the energy of an air conditioner. If you must buy an air conditioner, choose an ENERGY STAR® model designed for the size of room you intend to chill.