Reading R-values

The right way to choose insulation material

When it comes to specifying insulation, the type of product isn’t really an issue as far as the building codes are concerned. The codes don’t really care.

Go to any website that shows required insulation levels by Climate Zone, and you won’t find recommendations for foam over batts, or batts over cellulose. Instead, you’ll see target R-values. It’s the builder’s job to select the materials to hit that target, balancing budgets with preferences.

Foam offers superior penetration, air sealing and labor savings because there is no added work required to do air sealing, but it comes at a price. Batts cost less than foam on a square-foot basis, but if you have sloppy or expensive labor, those savings are quickly eaten up by having to redo the work that’s been installed incorrectly.

When choosing from among insulation types, a batt’s a batt, right? Not quite. A survey of insulation manufacturers — Johns Manville, Knauf, CertainTeed, Owens Corning and Icynene — shows that companies are highlighting the differences as they aim to win business. Here are some of the differentiation categories:

Recycled content: Many batt manufacturers include recycled content into their labels. Just 30% recycled content meets EPA guidelines. Knauf’s EcoBatt insulation Glass-wool boasts a 61.9% recycled content.

Binder: Binders are all formaldehyde-free now, and acrylic binders are now common. Knauf said its Ecose binder technology reduces its embodied energy by 70%, with no phenol, formaldehyde, acrylics or artificial colors.

Mold: Both ASTM and UL offer anti-mold standards for insulation. Johns Manville treats it with an EPA-registered preservative. Owens Corning applies a biocide to its QuietR duct board.

Smart membranes: CertainTeed’s Dry-Right batts feature MemBrain Smart Vapor Retarder & Air Barrier Film, a vapor retarder that changes permeability based on humidity.

Physical flame and fire retarders: The hot thing in fire protection today is intumescent coatings, used for foams, not batts. An intumescent coating swells with high heat, increasing its volume but decreasing its density, which can delay or even prevent ignition. Building codes rate un-faced batts as noncombustible. Still, Johns Manville FSK-25 faced batts offer a foil-scrim-Kraft facing that yields a 25/50 fire hazard classification.

Foams: Today’s foam manufacturers differentiate by their sustainable and green attributes, not by their R-value per inch, which is largely dictated by the physical properties of the foam. Look for foams without PDBE, a chemical flame retardant that is a bio-accumulative toxin.


This blow-in natural fiber insulation is engineered for use in wall and attic retrofit projects. 

Knauf Insulation

EcoFill Wx is an unbounded glass wool blowing insulation with post-consumer recycled content.

Owens Corning

EcoTouch fiberglass insulation for exterior wall cavities is easier to cut and split with less dust. (

Johns Manville

The company’s faced batts and rolls fiberglass insulation are lightweight and offer thermal and acoustical performance. Products are bonded with a formaldehyde-free binder to promote better indoor air quality and come in a variety of R-values. (

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