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Making Sense of Continuous Insulation

Everyone instinctively knows that when you go outside on a cold day, you must zip your coat to stay warm. It doesn’t matter how thick the coat is, if it’s left open, your body heat will leak out. The same is true with building insulation – no matter its R-value (thermal performance), if insulation isn’t continuous throughout the building envelope like a zipped coat, heat will escape – wasting energy and money.

To help ensure well-insulated buildings, since 2012 the International Energy Conservation Code (IECC) has required continuous insulation (CI) in the building envelope. The 2012 IECC prescribes how much insulation is required for each of the 8 U.S. climate zones, for various types of above grade walls, below grade walls, roofs and floors.

In addition to enhancing a building’s energy efficiency, CI helps reduce moisture damage in the building envelope by lowering condensation within the envelope assembly resulting from vapor diffusion.

Continuous insulation is defined in ASHRAE 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, as:

“Insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings. It is installed on the interior, exterior, or is integral to any opaque surface of the building envelope.”

Notably, this requirement eliminates the use of fiberglass batts installed between wall studs as the sole means of insulation, which had been common practice in light construction for decades. Such insulation can still be used, but a continuous insulation installed over the studs, such as rigid foam, must also be applied.

Types of rigid foam insulation

When choosing rigid foam insulation for CI, it’s important to keep in mind the performance attributes of the various types: expanded polystyrene (EPS), extruded polystyrene (XPS) and polyisocyanurate (ISO).


Recognized by its white color (or gray in the case of graphited infused EPS – GPS), EPS insulation has the highest R-value per dollar of the rigid foams. It provides about R-4.6 per inch of thickness (R-5 for GPS). Unlike other rigid foam insulations, EPS retains its R-value throughout its time in service. EPS is the most versatile of rigid insulations because it can be used anywhere in the building envelope – roof, walls, floors and even below grade since it dries quickly.


Mostly used in walls or below grade applications, XPS manufacturers typically brand their insulations with colors such as pink, blue or green to make them recognizable. XPS provides about R-5 per inch of thickness, and is priced midway between EPS and ISO.


Typically pale yellow, ISO is mostly (but not exclusively) used in roof assemblies. ISO panels provide up to R-6.5 (aged value) per inch of thickness. ISO R values start at about R-7 per inch, but degrade over time as the thermal-enhancing blowing agents used to make them diffuse out of the material.

Common building envelope applications for each rigid foam insulation type













Below grade




Saving on CI labor and material costs

Rigid foam insulations come in numerous product configurations, with options to help building professionals save on CI installation labor and material costs. For example, several rigid foam insulations are available in “fanfold” bundles. One such faced EPS product is made-up of 50 two-foot by four-foot panels, with each panel attached to its neighbor along one side. The bundles weigh less than 11 pounds each, so it is easy for one person to carry two bundles, which easily unfold to cover up to 200 square feet per bundle.

EPS fanfold bundles require fewer fasteners than other roof and wall insulations, and require about 60% fewer man hours to install than working with individual insulation sheets. As a result, roofers specifically can save up to $25 per square – or about, $12,000 on a 500 square (50,000 square foot) roof. The bundles also help speed insulation in walls and below grade applications.

Other rigid foam options speed insulation on roof recovers of standing seam metal roofs, building up sloped roofs, and providing insulation and drainage on below grade walls, among other applications. Check with your insulation supplier for available options.


Each iteration of the energy code becomes more stringent, but with numerous rigid foam insulation types on the market, it is not difficult to meet the IECC’s 2012 CI requirement.

Michael McAuley is the President of Insulfoam. McAuley has more than 20 years of experience in building material sales and production management, including 14 years at Insulfoam's sister company, Versico Roofing Systems, as the National Sales Manager and General Manager.

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