Fiberglass is an excellent insulator and has been widely used in the United States for decades in all types of construction. Although fiberglass insulation is available in many forms, we recommend that you only install a product that has been specifically designed for use in steel buildings. Steel building insulation consists of blankets of woven long-strand fiberglass that are laminated on one side to a vapor-barrier facing. When choosing fiberglass insulation, you will need to decide how thick a blanket and what type of facing best suit your needs.

The insulating quality of fiberglass blanket is directly related to the thickness of the material. In general, the thicker the insulation, the more it retards heat flow. The relative effectiveness of an insulator can be expressed as an "R-value." A full discussion of R-value is beyond the scope of this page, but most people have already encountered it. Below is a listing of the accepted R-values for fiberglass blanket insulation of different thicknesses when properly installed in metal buildings (higher numbers indicate greater effectiveness). Be aware that improper installation can significantly lower the effectiveness of insulation.

2"..... R-7
3"..... R-10
4"..... R-13
6"..... R-19

Note: Although our product offering includes 6" of fiberglass insulation in the walls and roof of a building, we do not recommend that you install blankets more than 4" thick. Thicker blankets may distort the sheeting and can become so compressed that they do not perform at the rated R-value. If you believe you need R-19 or higher, we suggest you consider combining a 4" blanket of fiberglass with reflective insulation.

The facing material of metal building insulation plays several important roles, and you should carefully consider your choice. Different facings vary in three key qualities: workability, permeability, and durability.

The workability of a facing refers to the temperature conditions required for installation. Cold causes some vinyl facings to become brittle, and these may crack or split during installation or shipping (which means we cannot sell it for delivery to colder areas in Winter). Not only does this kind of damage look bad, but it will seriously degrade the facing's ability to do its job as a vapor barrier. The comparison table at the bottom of the page lists the minimum temperature at which various materials can be safely installed.

The permeability (water vapor transmission rate) of a facing refers to the rate at which water vapor will pass through it. As described on the main insulation page, metal buildings need a good vapor barrier. The effectiveness of various materials is measured in "perms," and lower numbers mean greater resistance to moisture. For example, a 1.0 perm barrier will transfer up to 50 gallons of water a week into a 50,000 sq. ft. building while a .09 perm material will transfer only about 5 gallons (materials with a perm rating above 1.0 are considered ineffective). Most facings are layered with different materials, and the better ones usually incorporate polypropylene or some other essentially waterproof material (see the comparison table below for more info).

The durability (mullen bursting strength) of a facing indicates how well it stands up to physical stress without ripping or tearing, which is important because the facing is usually left exposed on the interior of a metal building. The least durable facings are made of one layer of unreinforced vinyl, which can be punctured or damaged by only light contact. Reinforced facings have a layer of "scrim" or mesh of fiberglass, nylon, or some combination of materials that help prevent the facing from tearing. When choosing facings, you should consider where and how the insulation will be used. For example, roof insulation will probably receive less stress than exposed wall insulation, which may be bumped or scratched frequently (see comparison table below).