Spray Foam - Lessons Learned

Once upon a time, on a project that shall not be mentioned, it was assumed that open-cell spray foam could be sprayed between the beam bottom flange and the tube steel to fill the cavity as shown in the detail below.  Not so.

First of all, while the foam is under pressure (1200 PSI), it is also heated to 125 degrees.  It melts previously applied foam.  Spraying it upwards melts it all and it just drips down.*

Second, the size of the spray nozzle is fairly large, making it difficult to spray through small openings.

Typical Spray Nozzle

*Closed cell foam is even hotter.  Spraying it into a closed space could cause spontaneous combustion.

THE SOLUTION

1. Fill the void between beam and sheathing with batt insulation down to the red outline, which is +/- the max throw into that cavity that can be realized.
2. Seal between beam flange and tube steel.
3. Spray the inside face of the beam and bottom of beam with up to 3” of foam (installer’s typical solution to this situation).

http://en.wikipedia.org/wiki/Spray_foams_(insulation)

http://en.wikipedia.org/wiki/Building_insulation_materials#Spray_foam