Metal Building Spray Foam Insulation

A bare metal building in North Texas has two problems: it soaks up summer heat, and it sweats. When warm, humid air touches steel that has cooled overnight or under an air conditioner, water condenses on the panels and drips on whatever is underneath. Closed cell spray foam fixes both. It bonds to the steel, keeps air off the metal, and adds real R-value in a couple of inches.

Why closed cell on steel

Closed cell foam is dense and rigid, about R-6.5 per inch, and at about 1.5″ thick it acts as a vapor retarder. Sprayed directly on the panels, it does what other insulation can’t:

• Stops condensation at the source. No air gap between the insulation and the steel means no surface for moisture to collect on.
• Seals every lap and fastener. Panel laps, screw holes and the gaps at the eave and base trim all get closed in one coat.
• Adds rigidity. The foam bonds panels to girts and purlins and quiets the oil-canning and rattle in wind and rain.
• Holds up. It doesn’t absorb water, sag or give pests a nest the way loose fiberglass does.

What about the vinyl-faced blanket insulation?

Many metal buildings go up with faced fiberglass blankets pulled under the roof and wall panels. When that facing tears, or after years of humidity, moisture gets into the fiberglass and it sags. If you have it, we will look at its condition on the measure. Sometimes it has to come out before we spray, and your quote will say so.

What we spray, and how thick

Most of our metal building quotes look like this:

• Walls: 1.5″ to 2″ of closed cell on the inside of the panels, between the girts.
• Roof: 2″ to 3″ on the underside of the roof panels, over the purlins.
• Doors and openings: we spray around roll-up doors and frame openings and mask the doors themselves.

If you plan to air condition the building, the roof gets the thicker number. If you just want to stop the dripping and take the edge off summer heat, 1.5″ to 2″ everywhere is a common budget choice.

Before we spray

The building needs to be dried in: roof and wall panels on, doors installed or framed. We cover the slab, windows, doors and anything stored inside. For buildings full of equipment, we work out a plan with you so we can move around the space. Foam that stays exposed in a working building may need an ignition barrier coating, depending on how the building is used. Your quote spells it out.

Spray area and price

Metal buildings are priced by the square foot of steel we spray, at a given thickness. A 40×60 building with 14′ walls and a 1/12 roof has about 2,850 square feet of walls and 2,400 square feet of roof, before doors and windows come out. Run your exact size in the spray foam calculator, or see how barndominiums and shops compare.

Metal building questions

Will spray foam stop my metal building from sweating?

Yes. Condensation forms when humid air reaches steel that is colder than the air’s dew point. Closed cell foam sprayed directly on the panels keeps that air off the steel, so there is nothing for moisture to form on. It is the most reliable fix we know for dripping roofs.

Can you spray over the old fiberglass blanket insulation?

No. Foam has to bond to clean, dry steel to work. If the old blanket insulation is in good shape, some owners leave it in the roof and we spray the walls only. If it is wet, sagging or torn, it should come out first so the foam can go on the panels.

Is open cell foam OK in a metal building?

Not on bare steel. Open cell lets moisture move through it, so humid air can still reach the cold metal and condense behind the foam. Closed cell is the right choice anywhere foam touches metal panels.

Do I need to empty the building?

Not completely. We cover equipment, vehicles and stored items with plastic, and we can work in sections if you need to keep using part of the building. Anything that can be moved out easily is worth moving.