To be effective, insulation must resist heat flow, fill the space completely and evenly, be durable, and for some locations, withstand exposure to heat or moisture. Different materials may be used at different locations in the house envelope depending on the space available, ease of access and other installation requirements.

In addition, consider the following:

• Is the material available locally?
• Is it relatively easy to install, especially for do-it-yourselfers?
• Is it the best buy for the space available (either high insulating value per dollar if you have a lot of open space, or high insulating value per thickness if space is restricted)?
• Can it conform to surface irregularities?
• Is it rigid enough to provide support for finished materials or resist pressures against its surfaces?
• Does any single type of insulation require more accessory products than another (e.g. fire protection, air and vapour barrier or framing)?

For proper application, material handling, safety equipment and protective clothing requirements, follow the manufacturer's instructions (see Health and safety considerations).

Choosing the right materials and installing them properly ensures the finished job lives up to your expectations. This chapter describes insulation, air barrier and vapour barrier materials.