Steel sweats in an Iowa winter. Closed-cell foam on the roof and walls stops the drip, cuts the noise and makes a shop or shed worth heating.
Tell us what the Des Moines property is doing and we'll take a look.
A bare steel roof is a condensing surface. On a clear night the metal radiates heat to the sky and drops below the temperature of the air inside the building; whatever moisture is in that air condenses on the underside of the panels and drips onto vehicles, equipment, hay and stored goods. With roughly 128 nights a year at or below freezing at Des Moines International Airport per NOAA's 1991-2020 normals, and swings from a 30 F afternoon to a 14 F night in January, the cycle repeats all winter.
The old fix is a vapor barrier under fiberglass blanket, and the old failure is that the blanket sags, tears around fasteners and eventually holds moisture against the steel. Closed-cell spray foam bonds directly to the panels, eliminates the air gap where condensation forms, and insulates at the same time. It is the standard approach for post-frame and steel buildings in cold climates for that reason.
Post-frame (pole) buildings used as shops, garages, storage and hobby space on acreages across Polk, Dallas, Warren and Madison counties. Machine sheds and livestock buildings where condensation and rust are the issue. Pre-engineered steel buildings used as commercial shops, warehouses and small industrial space in the metro's edge cities. Detached garages and outbuildings that an owner wants to heat for the winter.
The usual scope is closed-cell foam on the underside of the roof panels and purlins and on the wall panels between the posts or girts. Thickness depends on the use: a building that will be heated to shirtsleeve temperature is scoped differently from one that just needs to stay above freezing and dry. We will ask how you use the building and how you heat it, and size the foam to that.
The steel must be clean and dry, and the temperature of the panels matters; foam applied to a frosted or oily surface will not bond. Winter jobs are scheduled around that. The foam must be continuous over the purlins and at the eave and ridge; gaps there put condensing surfaces right back into the assembly. Where the building has a ridge vent or an open eave, the scope will say whether it stays open or gets closed, because a foamed roof is normally an unvented assembly.
Spray foam is combustible, and a heated shop with a wood stove or a welding bench is exactly where that matters. Exposed foam in a building that people occupy generally requires a thermal barrier or an approved intumescent coating; some agricultural buildings are treated differently under the code. The scope will state how the fire protection requirement is met for your building and use. If you are planning a permit, we can coordinate with the county or city building department.
Doors, overhead door headers and the base of the wall panels at the grade board are the common leak paths after the foam is in. The scope covers them.
The drip stops, which is why most owners call. The building also gets quieter in rain and hail, steadier in temperature through the day, and much cheaper to heat if you heat it, because the heater is no longer fighting an uninsulated steel skin with hundreds of fastener penetrations. Tools and equipment stop rusting from condensation. Stored feed and hay stay drier.
If the building is going to be heated and closed up, plan for some ventilation. A tight steel box with a propane heater and no air exchange builds up humidity and combustion byproducts. We will note that in the scope along with the fire protection requirement.
Questions
It depends on how you use and heat the building. A storage building that just needs to stop condensation needs less than a shop heated all winter. We will scope a thickness to your use and write it down; the crew checks depth with a gauge during the job.
The blanket has to come out first. Foam needs to bond to the steel, and the blanket is usually wet, torn and holding moisture anyway. Removal is part of the scope when that is what we find.
Yes. Closed-cell foam bonded to steel handles the temperature swings of an unheated building. The main thing to protect it from is fire and UV exposure, which the coating or thermal barrier requirement addresses.
Yes. Condensation control is the usual goal and closed-cell foam handles the humidity in those buildings well. Ventilation for the animals stays as designed; we insulate the roof and walls around it.
Tell us what the house is doing and we will come look at where the heat is going.
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