Insulation is manufactured from a variety of materials and in various forms. The most common types of insulation used in wood-frame housing are described below.
Batt insulation is made from fibres of glass, mineral or steel-mill slag spun together with a binding agent. The product comes in lengths and widths to fit standard framing spaces and in a range of thicknesses that provide different RSI-values (R-values). Most batt insulation is called “friction fit” because it is made slightly wider than the standard framing space and held in place by friction. Batts should not be compressed to fit a smaller space because this reduces the insulation value.
Loose-fill insulation is made of materials such as cellulose fibre and mineral wool fibre and is installed by pouring or blowing it into spaces between the framing. In attics, the loose fill extends above the top of the ceiling joists to raise the insulating level and reduce thermal bridging caused by the framing members. Loose fill insulation in walls must be installed behind a membrane that permits visual inspection to ensure there are no gapsor voids before the interior finish is applied.
Rigid insulation is manufactured in sheets or boards using materials such as polyisocyanurate and expanded or extruded foamed plastic
and is usually applied to flat surfaces such as walls. Extruded polystyrene has low moisture permeability and can be used in damp conditions such as on below-grade walls.
Semi-rigid insulation boards are made of glass or mineral fibres and usually applied to flat surfaces such as walls. They are more flexible than rigid insulation products and not as easily damaged by impact or bending. Some semi-rigid insulation has good drainage properties and can be used on below-grade walls.
Specially formulated polyurethane and isocyanurate insulations can be installed by spraying or injecting under pressure. The liquid sets into a rigid mass within minutes of installation. Some products develop heat or expand during the curing process. Ensure that the products being installed are approved for use in houses, and have a qualified contractor perform the installation under well-ventilated conditions.