fiberglass, cellulose and mineral wool insulated sheathing

Fiberglass, cellulose and mineral wool are the cheapest products used in cavity wall insulation; but they can also be used to insulate the exterior surfaces of both cavity and solid walls... Just pay attention to their advantages, inconveniences and alternatives.

Boards

Fiberglass, cellulose and mineral wool boards can be included in the walls - as their insulating sheathing -, and covered with brickwork or other siding. See image at right.

Sprayed-on Fibers

Instead of rigid boards, builders can use sprayed-on cellulose, fiberglass or mineral wool on the surface of the outer walls.

To install these fibrous materials, builders often use a set of lightweight frames, filling them with the insulation.

Advantages

Cellulose, fiberglass and mineral wool boards (and sprayed-on fibers of the same materials) offer a good insulation-value at a lower cost.

Disadvantages

Fiberglass, mineral wool (rock wool and slag wool) and cellulose fibers and batts can't be left exposed. They demand being sealed, namely to protect them around windows.

Cellulose (and in a less degree fiberglass or rock wool) are prone to problems involving moisture, and both involve a fragile surface - making them unsuitable for situations where they are subject to erosion, friction, collision, etc.

They also offer a poor fastening base, due to their insufficient strength.

Alternatives

There are several alternatives to fiberglass, rock-wool and cellulose sheathing, namely plastic foams of different types. These products offer higher energy-efficiency. See: Insulation Materials, Rigid foam materials, Spray-on insulation and spray-on foam insulation.

EIFS (Synthetic Stucco) and Structural Foam Sheathing are also two excellent (though more expensive) alternatives.