Squeezing spray cork with a gun for insulation?

[Garald]

I may or may not have told people here of how there used to be a tiny gap between a low side wall and the adjacent longitudinal beam in the attic. (My girlfriend and I discovered it indirectly - young wasps were getting in and failing to get out, thus turning our place effectively into a giant death fig.) The builders acknowledged there was a problem there and put some sealant, so that should be airtight now. However, you may remember how I went about with a thermal camera and saw that the top of that side wall was unusually cold.

 

So, I'm about to attack the problem with a tube of cork (which has the consistency of an extremely viscous liquid, a solid at first sight, thanks to some sort of vicious glue that - the packet warns me - can be abused as a drug) and a manual caulk gun.

 

 

I know this is too late for me to ask, but can you please tell me right away if this is an extremely stupid idea? It seemed natural, but now that I'm looking online for instructions, I'm only seeing people doing this for other purposes (e.g. joints in flooring).

Edited February 26 by Garald