Two excellent methods to block heat are insulation and shading. Insulation helps keep your home comfortable and saves money on mechanical cooling systems such as air conditioners and electric fans. Shading devices block the suns rays and absorb or reflect the solar heat.
Weatherization measures-such as insulating, weatherstripping, and caulking-help seal and protect your house against the summer heat in addition to keeping out the winter cold.
The attic is a good place to start insulating because it is a major source of heat gain. Adequately insulating the attic protects the upper floors of a house. Recommended attic insulation levels depend on where you live and the type of heating system you use. For most climates, you want a minimum of R-30. In climates with extremely cold winters, you may want as much as R-49. Again, check the above publications for more information.
Wall insulation is not as important for cooling as attic insulation because outdoor temperatures are not as hot as attic temperatures. Also, floor insulation has little or no effect on cooling.
Although unintentional infiltration of outside air is not a major contributor to inside temperature, it is still a good idea to keep it out. Outside air can infiltrate your home around poorly sealed doors, windows, electrical outlets, and through openings in foundations and exterior walls. Thorough caulking and weatherstripping will control most of these air leaks.
Shading your home can reduce indoor temperatures by as much as 20° F (11° C). Effective shading can be provided by trees and other vegetation and exterior or interior shades.