Closed-cell and open-cell spray foam for Des Moines houses, basements, crawl spaces and steel buildings. Scoped for a climate with about 6,180 heating degree days a year, not a generic brochure.
Tell us what the Des Moines property is doing and we'll take a look.
Fiberglass and cellulose slow heat by trapping air in fibers. They do nothing about air moving through them, and in a Des Moines winter that is where much of the loss happens: warm indoor air pushed up through the attic floor by stack effect, cold air pulled in at the rim joist and sill to replace it. Spray polyurethane foam expands into the cavity and cures against the framing, so it insulates and air seals in one pass.
That combination is why foam earns its cost in specific places. At the rim joist, where the band joist sits on the sill plate and every floor joist bay is a leak, two inches of closed-cell foam closes the whole band. On a crawl space wall it insulates and blocks ground moisture at once. On the underside of a steel roof it stops the winter condensation that drips on everything below. In a cathedral ceiling it lets a shallow rafter bay reach a real R-value.
In an open, accessible attic it is often not the best value for the bulk of the insulation. There, we air seal the attic floor with foam and then blow in loose-fill to depth. The scope will say which approach fits each part of your house.
Closed-cell foam is dense and rigid, roughly R-6 to R-7 per inch depending on the product, and at around two inches most closed-cell products function as a vapor retarder. It adds stiffness to what it is sprayed on and is the right choice below grade, at the rim, on steel and anywhere moisture is a concern.
Open-cell foam is softer and lighter, roughly R-3.5 to R-4 per inch, and vapor-open. It expands a lot, so it fills irregular cavities well, and it is a good fit for interior walls, sound control and some attic rooflines where the assembly is designed to dry inward. It is usually less expensive per inch but needs more thickness for the same R-value. We have a full page comparing the two.
Rim joists and sill plates in basements of every age, including the stone and brick foundations common in older neighborhoods on the east and south sides. Crawl space walls and the rim above them. Attic floor penetrations (top plates, chases, can lights, bath fans, the hatch) as the air-sealing step before blown insulation. Cathedral and vaulted ceilings, bonus rooms over garages, knee walls in story-and-a-half houses. Basement walls being finished. And the roof and walls of pole barns, machine sheds and shop buildings.
Des Moines's housing stock skews old: the Census Bureau's 2024 American Community Survey shows a median year built of 1963, with roughly a quarter of homes built before 1940. Those houses were framed with balloon framing and open wall tops in many cases, and the attic floor is a sieve. Foam is well suited to closing those big irregular openings that no batt will fit.
Iowa's statewide energy code is the 2012 IECC with amendments, effective June 1, 2014. For new homes in our climate zone it calls for R-49 ceilings, R-20 walls, R-19 or R-15 continuous on basement and crawl space walls, and a blower door result of 4 ACH50 or better. It does not apply to remodeling an existing house, but those are the targets we aim toward when a retrofit budget allows.
Spray foam is a combustible plastic. Where it is left exposed inside a living space or an attached garage, the residential code requires a thermal barrier such as half-inch gypsum; in attics and crawl spaces accessed only for service, an ignition barrier or an approved coating is required. Certain foam products are allowed to remain exposed at the rim joist within stated thickness limits. Our scopes call out the barrier requirement for each area so it is priced and installed, not discovered later.
Tightening a house also changes how it breathes. If you have an atmospherically vented gas furnace or water heater, the scope will note that combustion safety should be checked after the air sealing, and if the house ends up very tight, that mechanical ventilation may be warranted. That is not a sales point; it is how a tight building is supposed to be finished.
Questions
Cured polyurethane foam is inert and is used in millions of buildings. The concern is during application and the cure window, when the two components are reacting. That is why the crew wears supplied-air respirators, the area is ventilated, and occupants stay out until the manufacturer's re-occupancy time has passed. We follow the product's published guidance and put it in the scope.
No. To air seal the attic floor, the existing insulation has to be pulled back from the areas being sealed, and if it is contaminated, wet or badly settled it usually comes out entirely. Once the floor is sealed, insulation goes back on top. If the existing material is clean and dry, it often stays and gets topped up.
Closed-cell foam is a vapor retarder, which is what you want on a below-grade wall: it keeps ground moisture out of the framing behind a finished basement wall. Above grade, the assembly has to be designed so it can dry to one side. That is a design question we answer in the scope, not a reason to avoid foam.
Yes, including full wall cavities, rooflines and rim joists for new homes and additions across the metro, and we can coordinate with your builder on the blower door test the Iowa code requires. Most of our residential work, though, is retrofit on existing houses.
Tell us what the house is doing and we will come look at where the heat is going.
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