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Materials & Specificationsaka: spray foamaka: SPFaka: spray polyurethane foamaka: foam board

Foam Insulation

In Plain English

Insulation that expands or comes in rigid boards to fill gaps and provide high R-value per inch.

Definition

Foam insulation includes spray polyurethane foam (SPF) and rigid foam board products used to insulate walls, roofs, and foundations. Open-cell spray foam provides R-3.5 to R-4 per inch; closed-cell spray foam provides R-6 to R-7 per inch. Foam insulation also provides air sealing and, in some configurations, vapor control.

Why It Matters in Bidding

Foam insulation often costs more per board foot than batt insulation but delivers air sealing and higher R-value per inch, so estimators must compare systems on installed performance rather than unit price alone. Because spray foam doubles as an air barrier and sometimes a vapor retarder, choosing it can eliminate separate scopes, shifting how the envelope budget is allocated across trades.

Example

Comparing assemblies for a tight building envelope, an estimator prices closed-cell spray foam in the roof deck, noting it provides both R-value and air sealing so a separate air-barrier line can be removed from the bid.

Related Terms

Rigid InsulationBatt InsulationSheathingStructural Insulated Panel

Frequently Asked Questions

Closed-cell foam delivers higher R-value per inch and acts as a vapor retarder but costs more, while open-cell is cheaper, more vapor-permeable, and needs greater thickness for equal R-value. Estimators choose based on the target R-value, available cavity depth, moisture strategy, and budget for the specific assembly.
Spray foam requires specialized equipment, trained applicators, and chemical materials, raising the installed unit cost above fiberglass batts. The premium can be partly offset because foam air-seals and may serve as a vapor barrier, potentially removing separate sealing scopes and reducing energy-related life-cycle costs the owner values.
Closed-cell spray foam at sufficient thickness can function as an air barrier, and sometimes a vapor retarder, allowing the estimator to consolidate scopes. This must be confirmed against the specifications and energy code, since some projects still require a dedicated tested air-barrier system regardless of the foam.

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