An arched steel building is a curved sheet of metal with no insulation, no cavity and no flat surface anywhere on it. Around Bow Island there are a great many of them still in daily use, and in this particular climate the shape produces a problem that is specific to the sunniest part of the province.
Half the arch is a solar collector and half of it is not
On an arch running east to west, the south-facing portion of the curve presents a surface close to square-on to the sun through the middle of the day while the north-facing portion sees almost none of it. That is not a small difference. Through a long cloudless afternoon here the two halves of the same building are at substantially different temperatures, and the sheet is continuous between them. The result is a building with a one-sided interior climate, a sheet under constant differential expansion, and a cold half that is collecting whatever moisture the warm half's air is carrying.
Which is why the dripping is one-sided
Owners describe water coming off the inside of the arch on one side and not the other, and the usual conclusion is a leak. It is not a leak. It is the cold half of the shell acting as the condensing surface for the whole building's air, and there is nothing between that air and the steel. In this region the night-time radiant cooling under clear skies makes it worse, because the sheet drops below the outdoor air temperature after sunset and the condensation continues long after the sun is off the building.
What actually stops it
A bonded layer with no air space behind it. Closed-cell foam sprayed directly to the inside of the arch at two inches or more is both the insulation and the vapour control, and it eliminates the condensing surface rather than managing it. That is the only approach that works on this shape, and it is also why nothing else gets used: there is no cavity to fill, no framing to fasten to, no flat run on which to lay board, and anything hung inside the arch leaves a gap where the air and the water will go.
The substrate is the job
Foam bonds, so everything depends on what is behind it. An arch that has been in service for forty years has a film of dust, sometimes oil, and often loose surface rust on the inside. Foam will not key to any of that, and foam that does not key will come away in sheets. Preparation is a real and visible part of the quote on one of these buildings, and on a badly deteriorated arch the honest answer is that it is not a candidate.
The end walls are the oldest part of the building
The arch itself is usually sound. The end walls are where every change has happened: framed in timber, cut about to take a bigger door, patched where a machine clipped them, and often not the same material as the arch. They are also where most of the air moves. Dealing with the end walls is a framing and sealing exercise as much as an insulation one, and on most of these buildings it is where a disproportionate share of the result comes from.
Terminating at the bottom and dealing with the floor
The foam has to stop somewhere, and the bottom of an arch is where water collects. If there is a concrete curb or a knee wall the foam terminates on it cleanly. If the arch meets bare ground or a gravel floor, there is a moisture source nothing sprayed on the arch will address, and that needs resolving first. A knee wall under the arch changes the building considerably and is worth discussing before anything is specified.
One company, start to finish
Quonset spray foam insulation Bow Island gets handled by us from the walk-through onward. We quote and manage it, and our own installers apply the foam.
Quonset Spray Foam Insulation Bow Island: Common Questions
Why does only one side of the arch drip? Because the sun warms one half of the curve and not the other, so the cold half becomes the condensing surface for the whole building's air. It is not a leak.
Why is foam the only option on an arch? There is no cavity, no framing and no flat surface. Anything that leaves an air gap behind it leaves the condensation problem in place.
Does the inside need cleaning first? Yes. Foam bonds to what it meets, and it will not adhere to dust, oil or loose rust. On an older arch that preparation is a genuine part of the work.
How much does Quonset spray foam insulation cost in Bow Island? The arch area and the thickness set the foam. Preparation, the end walls and any base or curb work are the items that separate two buildings of the same span.
How do I choose a Quonset spray foam contractor in Bow Island? Ask what they will do about the end walls and how they will prepare the arch. A quote that covers only the curved area has left out most of the air leakage.
Size the arch with the R-value calculator, then get a free Bow Island quote. More on Quonset Spray Foam Insulation Alberta province-wide.