Insulate your Steel Building: Everything you Need to Know

Published February 3, 2017 by Whirlwind Team

Insulated metal building

When it comes to metal buildings, insulation addresses two important goals—stabilizing the structure’s interior temperature and preventing moisture from entering or collecting via condensation.

Insulating metal buildings is essential, because metal is a far better heat conductor than wood. Without insulation, the building cannot retain heat in the winter, while the walls and roof will transfer the sun’s heat indoors in the summer.

When temperatures vary noticeably between outside and in, condensation will form. Moisture allows unhealthy mildew and mold to grow, particularly harmful for people with allergies. Without proper building maintenance practices, moisture can also cause building rust and corrosion—something no home- or business-owner wants.

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Where insulation is installed between the studs with traditional construction materials, metal building insulation is typically installed over the framing to provide continuous coverage. This prevents any transfer of energy and/or moisture between the framing and the exterior roof and wall panels.

There are several different types of insulation commonly used for metal buildings. Not surprisingly, costs and benefits vary, so it’s important to match insulation characteristics with each building’s size and shape, geographic location, and intended use.

How does metal building insulation work?

Insulation controls heat flow, prevents condensation, and controls noise. Depending on the facing, some insulation could increase the efficiency and effectiveness of lighting fixtures.

Insulation slows the movement of heat and keeps it inside the building, where it belongs in the winter. In summer, it does the opposite, keeping heat outside. The heat transfer rate throughout the building is controlled, reducing energy usage.

The vapor retarder of blanket-type insulation also prevents the formation of condensation by blocking the passage of water vapor so it won’t condense onto the interior building surface or dampen the insulation fibers.

Insulation can also deaden noise from the outside and by absorbing reverberations inside. Lighting is more efficient because you can choose facings for their brightness and reflectiveness.

What are U-Values, R-Values and vapor retarders?

  • The U-value is a term describing the specific thermal performance of a building envelope assembly, like the roof or sidewall systems. A complete assembly with multiple heat flow paths has a particular U-value that depends on the materials within the series heat flow.
  • The R-value indicates how well the insulation works or its level of thermal resistance. Look for a high R-value, which means the insulation’s thermal resistance is high; in other words, it is a better insulator than one with a low R-value.
  • A vapor retarder is just what it sounds like. It is a facing that prevents or slows the flow of moisture through to the insulation it is attached to. A low “permeance” indicates a superior vapor retarder. Also, vapor retarders are typically required to be fire retardant.

Types of insulation

Loose fill

Loose fill is insulation made up of loose fibers or fiber pellets. The insulation is blown into building cavities rather like shooting water from a hose. It can be more costly than other types of insulation, but it can get blown into corners and places where a blanket might not fit.

Batt and blanket

Mineral fibers of rock wool or processed fiberglass make up batt and blanket insulation. Batt is very inexpensive but it must be installed carefully for full effectiveness.  Some versions have a radiant barrier backing, the best type for metal buildings. Blanket insulation is a rolled insulation cut to specific widths and lengths. Both batt and blanket have R-values of R-3 per inch.

Spray foam insulation

Similar in nature to loose fill, spray foam insulation comes as a liquid with a foaming agent and polymer such as polyurethane. It can be sprayed into walls, floors, and ceilings where it expands to fit the space. The insulation then hardens into a solid cellular plastic containing air-filled cells.

It easily fills all the nooks and crannies until they are airtight in areas you may not be able to insulate any other way. Spray foam is ideal for unusual shapes or areas with a lot of obstructions. More expensive than batt, it is a better air barrier.

Fiberglass insulation

This is the least expensive and most popular method of insulating metal buildings. Familiar to homeowners, it comes in rolls of “blanket” material. It can be installed by a non-professional, but it’s essential to wear a mask. Additional protective clothing is a good idea because fiberglass tends to shed fine fibers.

Fiberglass insulation for metal buildings is known as NAIMA 202-96R(Rev. 2000) insulation, meaning it meets the requirements of this particular NAIMA standard and has been certified by the National Association of Home Builders for its thermal performance in metal buildings.

Since it’s a soft batting, fiberglass sometimes attracts nesting bugs, rodents, or birds, and may absorb moisture. This is why metal building insulation is almost always provided with a protective facing or vapor barrier.

Not only does this offer protection against the concerns listed, it also adds an attractive finished appearance to the inside of the building. The facing is offered in a variety of styles and colors to suit your requirements.

Reflective foil

Sometimes called foil bubble, this type of insulation is waterproof, and the reflective surface can considerably brighten the building’s interior. Reflective foil insulation can be more expensive to purchase, but it’s clean and easy to install using staples, nails, or glue. It requires no mask or other protective gear.

Rigid board

Foam “rigid boards” are good for any climate. Typically made of polyurethane, fiberglass, or polystyrene, this kind of insulation is available in a variety of performance ratings and can be very effective for dampening noise as well as resisting heat and moisture.  The R-value can range from R-4 to R-8 depending on the thickness of the cut.

It’s relatively easy for a non-professional to install. If you plan to use this type of insulation, be sure to let your metal building provider know so that the proper accommodations can be made, such as longer fasteners and extended panel lengths.

Insulated panels

Insulated panels consist of an insulating foam core sandwiched between two metal panels. This panel eliminates the need for fiberglass blanket or rigid board insulation. Although more expensive than the other insulation options, insulated panels offer exceptional insulating properties, faster installation times, and a streamlined architectural appearance.


Proper insulation can muffle sound from interior equipment or activity as well as exterior noise such as rain, hail, traffic, or heavy machinery. It can save energy and, therefore, heating and air conditioning costs.

Insulation significantly improves return on investment for any metal building, keeping it clean and in prime condition longer and protecting the health of those using the building.

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