The question we get asked most often about an arch is how thick the foam should be, and the honest answer is that it depends on what the building is being asked to do. Quonset spray foam insulation in Leduc is worth deciding by working backwards from the use, because thickness is the main lever on the cost of one of these jobs and guessing at it is how people either overspend or fail to fix the problem.
Stopping condensation and holding a temperature are different targets
There is a thickness at which the interior surface stays above the dew point of the air touching it, and that is what stops the dripping. Beyond that, every additional inch is buying reduced heat loss rather than solving the condensation, and it only pays back if the building is actually heated. A cold storage arch that just needs to stop raining on the equipment does not need what a heated shop needs, and specifying it as though it did is the most common overspend on these buildings.
What genuinely changes the number
How the building is used and how warm it is kept. How humid the inside air is, because a building full of stored crop, a wash area or animals sits at a much higher dew point than one holding dry machinery. And how cold it actually gets where the building stands. Those three set the target; the product's value per inch does the arithmetic. It is a calculation rather than a rule of thumb, and anyone quoting the same thickness for every arch is not doing it.
Coverage matters more than depth past a point
A shell sprayed thoroughly at a modest thickness outperforms one sprayed thickly with the awkward areas skipped. The places that get missed are always the same: behind purlins, at the end-wall junction, around penetrations, and down at the base of the curve. Those gaps are where the cold surface survives and where the water then concentrates, so completeness is worth more than an extra inch on the easy parts.
Air sealing is the part that is not on the invoice
Foam applied to the shell is the insulation and the air barrier at once, and on an arch full of laps and fasteners the sealing does a large share of the work. That is why the improvement on one of these buildings is bigger than an R-value comparison alone suggests, and why a liner hung off the arch, which insulates without sealing, does not produce the same result.
Why the shape rules out the alternatives
There are no stud bays and no flat planes. Batt has nothing to sit in and rigid board cannot follow the curve without leaving voids that condense out of sight. Foam bonds to the shell and takes its shape, on clean dry steel, with active rust dealt with first rather than covered.
Quonset Spray Foam Insulation Leduc: Common Questions
How thick does the foam need to be? Enough to keep the inside surface above the dew point for how the building is used. On a Leduc building that follows how it is heated far more than how big it is. Past that you are buying heat savings, which only pay back if it is actually heated.
Is thicker always better? No. Full coverage at a sensible thickness beats a thick coat with the awkward areas missed, because the missed areas are where the cold surface survives.
Why is the improvement bigger than the R-value suggests? Because the foam is also the air seal, and on an arch full of laps and fasteners the sealing is doing a lot of the work.
Estimate the thickness with the R-value calculator, then get a free Leduc quote. More on Quonset Spray Foam Insulation Alberta province-wide.