The future of roofing insulation

August 14, 2015

Insulated metal panels are the most expensive roofing option, but they offer benefits that fiberglass and rigid foam boards do not. Photos courtesy Kingspan

By Jim Brock
When it comes to insulating a facility, insulation addresses two important goals—maintaining a consistent interior temperature and preventing moisture from forming and collecting via condensation.

There are several different materials and ways to protect a roof, including fiberglass, rigid board, and insulated metal panels (IMPs). Costs and benefits may vary between the products, but an overall building envelope comparison shows some marked differences.

Fiberglass insulation has traditionally been the most common in buildings with metal roofs. It can be installed as a single or two-layer system.

Single-layer system
In a single-layer system, blankets of insulation are rolled out atop the steel structure with the vapor retarder facing down and toward the inside of the building, thus creating a finished look. Seams where blankets meet are joined by folding and stapling the facing tabs or taping the joint to prevent water vapor from getting through the insulation and condensing on the roof.

After the insulation blankets are in place, thermal spacer blocks made from strips of foam are placed above the purlins before attaching the roof panels. The foam strips add insulation value where the insulation is compressed between purlin and roof sheet.

Two-layer system
The two-layer system is like the single-layer, over-the-purlin system. The difference is the first layer of faced insulation is allowed to drape between each purlin and a second layer of insulation is installed parallel to, and between, each purlin. This system also has thermal spacer blocks on top of the purlins and is called the ‘filled cavity’ system.

Both systems rely on the insulation materials being allowed to expand to their full thickness between the purlins to reach their greatest effectiveness. That usually does not occur and the actual thermal performance is less than what is normally published.

Rigid foam boards
Rigid foam boards are another form of insulation that can be used. The boards do not need to expand and will not compress between the roof and the purlins. The thermal performance is consistent and different R-values can be achieved with varied board thicknesses or extra layers.

Costs for rigid foam board insulation systems are higher than fiberglass systems, but the installation method is similar to the single-layer system. Foam boards are placed perpendicular across the purlins and run from the eaves to the ridgeline. Additional layers are staggered to cut seams between boards from lining up.

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

The Installation of IMPs is much quicker than any other roofing system because it is a complete system in a single source product. 

Insulated metal panels
IMPs are another option when specifying roofing insulation. In a direct, product-to-product cost comparison, insulated metal panels are the most expensive, but in Comparing the total cost of the roofing system, they show their true savings.

A properly designed and installed roofing system features four critical components, a water barrier, air barrier, thermal barrier, and vapor barrier. Fiberglass and rigid foam board certainly cover the thermal aspect, and can sometimes also offer water or vapor barriers, but it do not serve as air barriers. Other components and additional installation time are required to complete these other types of roofs.

Insulated metal panels are the only system that offers a complete envelope in one single-source product. Installation is faster, buildings are more quickly closed in, and performance of the panels remains the same for the roof’s lifetime. If the ever-increasing thermal requirements and changes in building codes are factored in then it is clear insulated metal panels can be a viable choice.

Jim Brock Headshot[3]Jim Brock has more than 30 years’ experience and is currently the roof product manager for Kingspan Insulated Panels. Brock previously held positions with MBCI, American Buildings, Ersystems, and Viridian Systems. He also has experience with the contractor side of the industry. Brock can be reached at[4]


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