A steel building is the hardest common structure to insulate well, because the frame itself works against you.
This page is about the structure type rather than the use. Whether it is a shop, a storage building or a warehouse, if it is steel, the same physics apply.
Steel conducts, and the frame is continuous
Wood framing is a poor conductor. Steel is an excellent one, and in a metal building the structural members run continuously from the cold exterior to the warm interior.
Every purlin and girt is therefore a thermal bridge - a direct path for heat to leave and, more importantly, a strip of surface on the inside that is markedly colder than the panel around it.
That is why the classic failure in a metal building is not a general chill. It is stripes: lines of condensation, frost, rust or staining that follow the framing exactly. People often assume the building is leaking along those lines. It is not. Those are simply the coldest interior surfaces, and the moisture in the air is finding them.
Why blanket insulation struggles
The standard fibreglass blanket draped over the purlins and pinched under the sheeting gets compressed where it crosses the steel - precisely where the thermal bridge is worst. It is thinnest exactly where you need it thickest.
It also does nothing about air movement. Air passes around it through laps, at the eave, and at every penetration, carrying moisture straight to the cold steel behind.
Closed-cell foam applied directly to the underside behaves differently. It adheres, so there is no gap for air to travel in; it is continuous over the purlins rather than compressed against them; and at adequate depth it holds the dew point inside the foam instead of on the steel face.
That is the whole argument for foam in a steel building. It is a moisture-control argument first and a thermal one second.
The Calgary variable
Chinook cycling means the steel repeatedly crosses the dew point through winter instead of sitting steadily cold. Condensation forms, clears, forms again.
The practical signature is intermittent damp - wet patches that appear during a swing and are gone days later - rather than a constant drip. If that is what you are seeing, chase the assembly rather than the roof.
Repeated wet-dry cycling on unprotected steel and fasteners is also what drives corrosion over time. See preventing rust in a steel building.
What to settle before the quote
What the building is used for, and whether anything inside adds moisture to the air.
Whether it is heated continuously or intermittently. Intermittent heating is the harder case and changes the recommendation.
The covering requirement. Foam generally needs an appropriate thermal barrier over it, and that must be in the quote rather than discovered later. See thermal barrier vs ignition barrier.
What we do
We are a referral service. We do not install. We connect you with vetted installers - certification, insurance and WCB standing checked.
No price without a site visit. Get a quote.
See also metal buildings and stopping condensation in a metal building.