If there is no vapor retarder, insulation is usually the first component installed over a roof deck (see picture).

The purpose of insulation is to help keep heat in a building in cold weather. It also helps keep heat out of a building in hot weather. Insulation saves money because the air-conditioning and heating systems will not be used as much. Some buildings do not need insulation. It is not used with every roof system.

Insulation can be used to make slope on flat roofs. It can be tapered to buil some slant into a roof system. Tapered insulation is manufac-tured so that the pieces are sloped (see picture).

Insulation can be installed three different ways. It can be mechanically attached, loose laid or adhered with adhesive.

You have already learned how insulation fits with other components of a roof system. Now the material itself will be discussed. The most common types are boards. These kinds of insulation are rigid (see Figure 16). They are made of different types of materials.

Rigid board insulation can be tapered. As mentioned before, tapering makes insulation sloped so it creates drainage. Some boards have a special surface called a facer.

There are many types of insulation.

Three common types of rigid board insulation are perlite, wood fiber and polyisocyanurate foam.

Perlite roof insulation boards are made of a volcanic ore. This ore is combined with organic fibers and binders. The top surface is usually treated with an asphalt coating (see picture 17).

Wood fiber insulation looks a lot like perlite. But it is made of wood fibers that are glued together.

Polyisocyanurate foam is also known as Iso board. It usually has an asphalt felt or a fiberglass facer on both sides.

There are two types of rigid polystyrene insulation boards.

Expanded polystyrene is usually called EPS or bead board.

Extruded polystyrene looks somewhat like expanded polystyrene. But it has a smooth, skin-like surface.

Composite Board

Composite board insulation is made of two layers of insulation (see Figure 18). The two layers are different types of insulation bond-ed (glued) together. There usually is a facer on one or both sides.

A rigid insulation layer can be laminated to OSB or plywood. This is an insulated deck that is nailable.

Other composite boards are coated with asphalt or some other facer materials. Other facer materials include foils, organic and glass fiber felts. and kraft paper.

Cellular Glass Roof Insulation

This insulation is formed out of heat-fused glass cells. It is available in flat and tapered boards.

Glass Fiber Insulation Board

This is made of bonded glass-fiber wool. Kraft paper is adhered in asphalt to the top surface.