Almost every steel building we are called to around this town already has insulation in it, and that is the complication. When the kit was erected, a faced fibreglass blanket was rolled out over the purlins and girts and the cladding was screwed down through it. The owner believes the building is insulated. The building behaves as though it is not. Both of those are true, and what to do about the blanket is the first decision on the job.
What happens to a blanket under screwed-down cladding
The blanket is compressed to almost nothing at every purlin and girt line, because that is where the screws pull the cladding tight. So instead of a continuous layer you have a series of thick pillows separated by lines of nearly zero insulation, every few feet, over the whole building. Those lines are visible from inside as stripes of condensation or frost in cold weather, and from outside after a light snow as a pattern of melted lines on the roof.
The facing is a thin vapour-retarding film, and it is lapped rather than sealed. Over a decade of movement, dust, birds and the occasional ladder, those laps open and the film tears. Once it is torn, moist building air reaches the back of the cold steel and condenses there, behind the insulation, where nobody can see it and where the fasteners are.
Why foam cannot simply go over it
Foam has to bond to what it is sprayed onto. A loose, torn, dusty plastic facing is not a substrate: the foam will adhere to the film in places and not in others, and the blanket behind it becomes a trapped layer with moist air in it and a cold steel surface beyond. That is worse than leaving it alone.
So there are two honest routes. Take the blanket out and spray closed-cell directly to the inside face of the cladding and over the girts, which gives one continuous adhered layer with no cold lines and no trapped cavity. Or leave the blanket in place, frame an inboard liner, and spray the inside face of that framing, accepting that the steel itself stays cold and the assembly is more complicated. The first route is nearly always the right one and we will tell you if yours is the exception.
What the continuous layer actually fixes
Closed-cell at about R-6 to R-7 per inch bonded to the steel does three things at once. It removes the cold surface, so there is no plane for building moisture to condense on. It seals the laps in the cladding and the fastener penetrations, which are the air paths. And it stops the thermal bridging at the girt lines, because the layer is continuous across them rather than squashed at each one.
The corrosion argument is the one that matters most over the life of the building. Dry steel with foam bonded to it does not have condensate sitting against it, and the fasteners are the components that fail first when it does.
Before anything is sprayed
The inside face of the cladding has to be clean, dry and sound. That means the blanket out, the dust and bird debris off, any loose rust dealt with, and any existing leak at a lap or a fastener fixed, because foam over a live leak hides it rather than stopping it. On an existing building that preparation is a real line in the quote and a contractor who does not mention it has not planned to do it.
If the building is still on order
Say so. A building that has not been erected yet can be ordered without the blanket, which saves buying material that then gets thrown away, and the girt depth and liner details can be settled before the steel arrives rather than worked around afterwards.
We take care of the work
Nobody gets handed your metal building spray foam insulation Coaldale job. We quote the job, schedule it and stand behind it, and our crews are the ones who show up.
Metal Building Spray Foam Insulation Coaldale: Common Questions
Our building has insulation already. Why is it cold? Because the blanket is crushed flat at every purlin and girt, so the layer is interrupted every few feet, and the facing has almost certainly torn.
Can you spray over the existing blanket? Not and have it work. Foam needs to bond to the substrate, and a loose torn facing is not one. The blanket comes out or a liner goes in.
Why do the screws rust first? Because condensate forms on the cold steel behind a failed facing and sits against the fasteners. A bonded layer with no gap behind it removes the condensing surface.
How much does metal building spray foam insulation cost in Coaldale? It is priced per board foot over the sprayed area, so wall and roof area times thickness sets the material. Removing the existing blanket and preparing the steel is a separate line and on an older building it is a real one.
How do I choose a metal building spray foam contractor in Coaldale? Ask what they intend to do with the blanket that is already in there. If the answer is to spray over it, you have found the quote to set aside.
Size the assembly with the R-value calculator, then get a free Coaldale quote. More on Metal Building Spray Foam Insulation Alberta province-wide.