TL;DR
Rigid foam board is sheet insulation in three main chemistries—expanded polystyrene at about R-4 per inch, extruded polystyrene near R-5, and foil-faced polyisocyanurate at R-6 or better—sold in 4x8 sheets from half an inch to several inches thick. Boards insulate where batts cannot: continuous exterior sheathing that breaks stud thermal bridging, foundation walls, slab edges, and crawl spaces.
What it means
Rigid foam board is sheet insulation in three main chemistries—expanded polystyrene at about R-4 per inch, extruded polystyrene near R-5, and foil-faced polyisocyanurate at R-6 or better—sold in 4x8 sheets from half an inch to several inches thick. Boards insulate where batts cannot: continuous exterior sheathing that breaks stud thermal bridging, foundation walls, slab edges, and crawl spaces. Building codes require an ignition or thermal barrier such as drywall over foam left exposed indoors.
Where it sits in the glossary
Rigid foam board is part of the Trade jargon group inside the ProFix Directory glossary. Browse every term in this category from the glossary index.
Why Ohio homeowners should know it
This is a term Ohio homeowners encounter when reading contractor quotes, hiring paperwork, or inspection reports. Understanding it well enough to ask one good follow-up question is usually all the protection a homeowner needs.
ProFix Directory keeps definitions short on the index page and saves the longer context — Ohio-specific rules, where the term comes from, and which ProFix tools touch it — for these per-term pages so the term is easy to cite and easy to share.
ProFix tools that touch this term
See also
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