Spray Foam Insulation in Des Moines, IA

Spray foam insulation is mixed at the gun, sprayed as a liquid and expands to fill the space before it cures, so one pass both insulates and stops air. That combination is why it suits the cold, leaky spots in a central Iowa house, where a January night averages about 13.8F at the Des Moines airport according to Wikipedia's climate table. We spray two kinds of foam, and choosing between them is the first decision on every job.

Closed cell vs open cell

Closed-cell foam cures hard. HomeGuide rates it at R-5 to R-7 per inch, and at typical thickness it works as a vapor retarder and does not take on water. It also adds stiffness to the wall or deck it is sprayed on. Open-cell foam is soft and expands far more, at about R-3.5 to R-3.7 per inch. It seals air well and deadens sound, but vapor passes through it, so in Climate Zone 5 it needs a vapor retarder or an assembly that can dry.

Around Des Moines that pushes closed-cell toward rim joists, basement walls, roof decks over vaulted ceilings and the steel in shops and pole buildings. Open-cell earns its place in interior walls, between floors, and in attic rooflines where the moisture plan is sound.

Thickness against the code table

Iowa's version of the 2012 IECC lists R-20, or R-13 plus R-5 continuous, for wood-frame walls in Zone 5 and R-49 for ceilings. Closed-cell reaches high values in a few inches, which matters in a 2x4 wall or a shallow rafter bay where batts cannot fit. Under a roof deck with no attic, getting a high R-value while still leaving a vent channel is hard, and closed-cell solves that. We size the thickness to the target and put both numbers on the quote.

Where foam does the most good

The rim joist is our most common foam job: the band of framing on top of the foundation, which in most metro basements is bare wood or has a loose piece of fiberglass pushed against it. Two to three inches of closed-cell seals and insulates it in one step. Other good spots are kneewalls and the floors behind them in story-and-a-half houses, floors over garages and cantilevers, walls in additions while the studs are open, and cathedral ceilings.

When we say no to foam

Foam does not fix a leak. If a roof, window or plumbing leak is wetting the framing, it gets repaired first, or the foam will hide the rot. Foam should not go over knob-and-tube wiring, or over vermiculite that may contain asbestos, until those are dealt with. And on an open attic floor, sealing the gaps and blowing loose fill on top usually reaches R-49 for less. We tell you which parts of the house are worth foaming and which are not.

Curing and re-entry

Before we spray, we cover floors and belongings, mask windows and outlets, and set up ventilation. HomeGuide advises staying out for 24 hours or more while foam cures. The surface and the material need to be inside the maker's temperature range, so for unheated attics and buildings in winter we bring heat or pick a better day. Once cured, foam does not settle or sag. Get a free estimate