Do frost lines where studs are on a wall show a failure of spray foam insulation?

Gerald Crozier Published: July 22, 2019, 10:24 p.m.Last updated: July 29, 2019, 11:08 a.m.

I have a customer with frost problems whose home shows every stud from the outside on a winter day. Would you say their spray foam insulation has failed?

Responses (1)

Mike Reynolds
Mike Reynolds July 29, 2019, 10:26 a.m. Reply


Hi Gerald,

It's hard to ever weigh in on a problem with complete confidence without seeing a project or knowing the full wall assembly, but if anything, that may actually show a 'success' of the spray foam rather than a failure. The wood studs will transfer far more heat than the Spray Polyurethane Foam (SPUF), so what you are seeing could actually be an indication of how important it is to include seamless insulation in a wall assembly.

The best method of wood frame construction would always include continuous insulation on the exterior of walls, without that you may see indications of thermal bridging through studs in the form of frost lines. The temperature on the exterior of the wall where the studs are would be higher than the temperature adjacent to the stud bays since they are filled with spray foam (SPUF), and so it may melt the frost.

Feel free to send us more details or pics of the wall. I am also a bit curious as to how it showed the studs from the outside if there siding installed with an air space, is the wall still under construction and it was frost forming on the exterior sheathing?