A very large number of Calgary houses built between the mid seventies and the late eighties have a vaulted living room, and almost all of them share the same problem. Ceiling spray foam insulation in Calgary is usually a depth problem before it is anything else.
The rafter is the whole constraint
Those ceilings were commonly framed in two-by-eights or two-by-tens, and a fair amount of that cavity was meant to stay empty for ventilation. That leaves five or six usable inches to hit a number that today would be closer to R-50 in a flat attic. Batt cannot do it in that depth. No product can, if it is measured per inch. The only way the assembly gets close is with a material that carries a much higher R-value per inch and does not need a vent channel taking a third of the cavity.
Unvented is a design decision, not a shortcut
Closing off the venting and insulating tight to the underside of the deck is a legitimate assembly and it is what most of these ceilings end up as. It is also a decision that has to be made deliberately and completely. Half-venting a cathedral ceiling - some baffles left in, foam partway up, a soffit still open at one end - produces an assembly that is neither one thing nor the other, and that is where the failures come from. Committing to unvented and detailing it properly is safer than a compromise.
Skylights, beams and the places it goes wrong
Vaulted ceilings in this era are rarely a plain slope. There is usually a ridge beam, often a skylight shaft, sometimes a knee wall where the vault meets a flat section. Every one of those is a break in the insulation plane and a break in the air barrier, and they are where the staining and the cold spots appear. Foam is used on these ceilings largely because it can follow a shaft and go around a beam as one continuous layer rather than being cut to fit.
The infill flat roof
The other common Calgary version of this job is the inner-city infill or the flat-roofed addition, where there is no attic at all and no slope to vent. Those decks cannot be ventilated in any meaningful way, so the assembly has to work without ventilation from the start.
Ceiling Spray Foam Insulation Calgary: Common Questions
Why can a vaulted ceiling not just take more batt? Because there is nowhere to put it. The rafter depth is fixed, and a vented assembly gives up part of that depth to the vent channel, so the number is limited by geometry rather than by product choice.
Is closing off the ventilation safe? It is a recognised assembly when it is done completely. The risk comes from doing it halfway, where some venting is left and some is sealed, which is neither assembly working properly.
What about the skylight shaft? It is usually the worst-performing part of the ceiling. The shaft walls are a break in both the insulation and the air barrier, and treating them as part of the same continuous layer is what stops the cold spot around them.
Work out what fits the cavity with the R-value calculator, then get a free Calgary quote. More on Ceiling Spray Foam Insulation Alberta.
After the foam: the interior finish
Spray foam does not get left exposed in a living space -- it has to be covered, and drywall is what does it. We work alongside boarding and taping in Calgary, an independent drywall contractor, so the two stages are not left to collide on site.