Quonset Spray Foam Insulation Alberta

Why conventional insulation fails on an arch

Batt insulation needs a cavity with parallel sides. An arch has neither. Installers who try it end up strapping the inside of the ribs to create a false cavity, which costs more in framing than the insulation itself and still leaves a continuous thermal bridge at every rib.

Rigid board fails for the same reason. A flat sheet against a curve touches at one point and gaps everywhere else, and those gaps are where the air moves and the moisture collects.

The condensation problem is the real problem

Most Quonset owners come to us about heat. What they actually have is a moisture problem that heat is making worse.

Bare steel in an Alberta winter sits at or below the dew point of the air inside. Warm, humid interior air - from a running engine, a livestock pen, a wash bay, or simply the sun heating stored grain - meets that cold skin and condenses. The result is the rain-indoors effect: water running down the inside of the arch, dripping onto equipment, pooling on the floor, and rusting the shell from the inside out.

Closed-cell spray foam ends it in one pass, because it is both the insulation and the vapour retarder. There is no interior surface left at the dew point for water to form on.

What closed-cell does in a Quonset

• It conforms. Sprayed directly to the inside of the arch, it follows every corrugation and rib with no framing, no fasteners and no gaps.
• It stops the sweat. At the thicknesses used on steel buildings, closed-cell controls vapour drive as well as heat loss.
• It stiffens the shell. Cured closed-cell bonds to the steel and adds real racking resistance to a thin-gauge arch.
• It seals the hard parts. End walls, door headers and the ground-level seam are where a Quonset leaks most, and they are exactly where foam outperforms every alternative.

Thickness and R-value

Most Alberta Quonsets land between two and three inches of closed-cell for unheated storage, and three to four inches where the building is heated and worked in through winter. At roughly R-6 per inch, that is R-12 to R-24 - and because the layer is continuous with no thermal bridging at the ribs, the effective performance is closer to the nominal number than any framed assembly achieves.

The right number depends on what the building does, not on its size. Use the calculator for a board-foot estimate, and see spray foam insulation cost for how Quonset pricing is built up.

Quonset Spray Foam Insulation Alberta: Common Questions

Can you spray foam a Quonset that already has insulation in it? Only after the old material comes out. Foam will not bond to sagging, damp fibreglass or to loose vapour barrier, and spraying over a failed blanket traps the moisture already in it. Strip-out is real labour and it is the line most often missing from a cheap quote on an older building.

Will foam make a Quonset warm enough to work in year-round? Yes, and this is the most common reason Alberta owners do it. Three to four inches of closed-cell plus a modest heater will hold a working temperature in a building that previously could not be heated at any cost.

Does it need a vapour barrier over top? Closed-cell at the thicknesses used here is its own vapour retarder. Adding poly over it can trap moisture between two impermeable layers, which is worse than either alone. We confirm the assembly for your build.

Can it be sprayed over a dirt or gravel floor? The arch can be foamed regardless of floor type, but a bare ground floor keeps pushing moisture into the building. Where the Quonset is heated, sealing the floor is usually the next conversation.

Get it quoted properly

No Quonset gets a price without someone seeing what is in it now. We quote from a site visit, and the answer changes more with what is currently on the arch than with the square footage.

Get a free quote. See the agricultural hub, metal buildings and machine sheds.