In Plain English
Quick Answer
Stiff foam boards used for insulation where space is limited or continuous insulation is required.
Definition
Definition
Rigid insulation consists of stiff foam boards made from expanded polystyrene (EPS), extruded polystyrene (XPS), or polyisocyanurate (polyiso), used for thermal insulation of walls, roofs, and foundations. R-values range from R-3.8 per inch for EPS to R-7.5 per inch for polyiso. Rigid insulation is used where space is limited and in continuous insulation applications to eliminate thermal bridging.
Context
Why It Matters in Bidding
Rigid insulation is increasingly specified as continuous insulation to meet energy codes, and its R-value per inch and board type drive both material cost and assembly thickness in the bid. Estimators must read the wall and roof sections carefully because polyiso, XPS, and EPS differ in price and performance, and continuous-insulation details add fastening, furring, and labor often missed in a quick takeoff.
Example
Example
Pricing an exterior wall assembly, the estimator takes off 4,800 square feet of 2-inch polyiso continuous insulation, then adds long fasteners, Z-furring, and the added labor the continuous-insulation detail requires beyond cavity batt.
See Also
Related Terms
FAQ
Questions Contractors Ask
How is rigid insulation quantified in a takeoff?
Estimators measure the wall or roof area in square feet, account for board thickness needed to hit the specified R-value, and add waste for cuts. Continuous-insulation assemblies also require special fasteners, furring, and detailing labor, so the takeoff captures more than just the board area to reflect true installed cost.
What is the difference between EPS, XPS, and polyiso for estimating?
They differ in R-value per inch and price: EPS is lowest cost and R-value, XPS is mid-range with good moisture resistance, and polyiso offers the highest R-value per inch but costs more. Estimators price the specified type because substituting changes both material cost and the thickness needed to meet code.
Why does continuous insulation increase bid cost?
Continuous insulation wraps the structure to eliminate thermal bridging, which requires longer fasteners, furring or cladding attachment systems, and careful detailing at openings. These add material and labor beyond the board itself, so an estimator who prices only the foam area understates the assembly and risks an underbid.
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