About 61 percent of Medicine Hat homes were built before 1991 - the oldest housing stock of Alberta's tier-one cities. In older houses the attic is usually where the largest, cheapest gain is sitting, and that is the assembly where open-cell spray foam makes the most straightforward financial case in this city. Open cell spray foam insulation in Medicine Hat is the cheaper route to attic depth where headroom allows it.
Depth is free in an attic, so buy the cheaper R
Reaching R-38 takes roughly eleven inches of open-cell or roughly six inches of closed-cell. In a vented attic with headroom, nothing is gained by paying for the denser material to occupy less space that nobody was using. Open-cell runs R-3.5 to R-3.8 per inch at about 0.5 lb per cubic foot; closed-cell runs R-6 to R-7 at about 2 lb. Where the only constraint is money rather than depth, the arithmetic is not close.
But air-sealing is what actually changes the bill
The mistake is treating attic insulation as a depth contest. The ceiling plane below it is full of penetrations - pot lights, bathroom fans, top plates, plumbing stacks - and heat leaves through those as air, not through the insulation as conduction. A sound attic job seals the plane first and insulates second. In a wide-daily-swing climate like this one, where the assembly is pushed one way by day and the other by night, an unsealed ceiling gets found quickly.
Interior walls, the other half of the job
Open-cell's soft, open structure absorbs sound, which makes it the material for partitions, demising walls, home offices and the wall against an attached garage. Established areas like Crescent Heights, Norwood, Ross Glen and Terrace tend to have solid but noisy interiors, and this is a cheap improvement that owners notice daily.
The line it does not cross
Open-cell is vapour-permeable and absorbs moisture. It is interior-only: never below grade, never in a crawl space, never on a rim joist, never bonded to steel. The industrial buildings in Brier Park and the Southeast Industrial area are closed-cell work for exactly that reason - the job there is removing a cold condensing surface, and a permeable foam cannot do it.
Foam facing occupied space needs a thermal barrier - 12.7 mm drywall or an approved intumescent coating - and an ignition barrier is permitted where access is for service only. Open-cell sits under its own CAN/ULC standard rather than S705.1.
Getting it wrong is expensive to undo
Spray foam adheres to the structure, which is exactly why it works and exactly why removing it is costly - industry figures for a full removal run well into five figures, and it is disruptive work. That asymmetry is the real argument for spending time on the specification rather than the price. The wrong foam in the wrong assembly is not a cheaper version of the right one; it is a cost you pay twice. On older housing especially, where assemblies are frequently not what the drawings said they were, an installer who opens something up and re-specs on the spot is worth more than one who quotes from the driveway.
Open-Cell Spray Foam Insulation Medicine Hat: Common Questions
Is it the cheaper route to attic R-38? Yes, where there is headroom - about eleven inches of it reaches the same target as six inches of the dense product.
Should I just add depth then? Seal the ceiling plane first. Heat leaves through pot lights, top plates and bath fans as moving air, and depth over an unsealed plane sits above the actual problem.
Where is it the wrong answer? Below grade, crawl spaces, rim joists and anything bonded to steel - including the industrial buildings in Brier Park and the southeast.
Work out both options with the spray foam calculator, then get a free Medicine Hat quote. More on open-cell foam province-wide.