If it goes to 90 or 100 degrees where you live and you absolutely need to run the Air Conditioning to keep your house cool only run it after 9:00 pm. There is less strain on your AC unit and typically you will pay far less for the Electricity to run the AC on Off-Peak hours. (8.7 cents versus 19 cents per KW Hr in Ontario)
If your home is well insulated with good vapour and air barrier the house should stay cool all day long. Even when it is 90 degrees outside.
If you live in an old drafty home with little insulation and no vapour or air barrier it may be better to look for a newer house, or build your own with double wall, and double Insulation. I recommend a small bungalow (1,000 sq ft) with a large basement since it is always warmer on a second floor. If possible design your house so that the bedrooms are in the basement, where it is always cooler.
If it is a comfortable temperature in your house and it is hot outside keep the windows closed. If it is cooler outside and a good breeze then open the windows on each side of your house and place a fan that blows out one of the windows. This creates a negative pressure and will draw the cool air into your house.
Plant lots of Maple Trees on the South Side of your house. Not so close that the roots damage your foundation but at a distance so that the mature trees will provide shade to the South side of your house. The October Glory or Autumn Blaze Maple are fast growing trees that will turn a Brilliant orange and red each fall. The leaves drop by winter and allow the Sun to heat your home during the winter.
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