Spray Foam Insulation in Oklahoma City: Closed-Cell, Open-Cell & Hybrid Systems

How These Systems Differ

Spray polyurethane foam starts as two liquids mixed at the gun and expands into insulation that bonds to whatever it touches. That adhesion is the real difference from batts and loose-fill: foam seals the cracks, plate joints and odd shapes fibrous insulation leaves open, so it stops air as well as slowing heat. In climate zone 3, where cooling is the dominant load and humid summer air finds every gap, stopping that air is often worth as much as the R-value. Foam is also a combustible plastic, so in most places people use it needs a thermal barrier over it.

The two foams differ in almost every practical way. Two-pound closed-cell is dense and rigid, commonly about R-6 to R-7 per inch, resists water and at about an inch or two is commonly a Class II vapor retarder, so it belongs on crawl space walls, rim joists, the underside of bonus-room subfloors, concrete and steel. Half-pound open-cell is soft and light, commonly about R-3.5 to R-3.8 per inch and vapor-open. Its big Oklahoma job is the underside of the roof deck, bringing attic ductwork inside a conditioned attic, along with vaulted ceilings and interior walls for sound.

The rest of the category is about using foam with judgment. Flash-and-batt and flash-and-blow put a closed-cell coat where the air leaks are and fill the remaining depth with cheaper batts or blown fill. Under-slab insulation, mostly rigid board with foam around congested plumbing, keeps a radiant floor from heating the clay below it, and it is a niche here. Intumescent coatings such as DC315 give exposed foam in shops, barns and crawl spaces a listed alternative to drywall when they are matched to that foam. Most projects need one or two of these, not all five.