foam inside the window frame

[banjodeano]

A thought has come to me folks, when i replace my upvc window frames, the window frames are hollow, would it be beneficial in trying to insulate the frames by squirting foam into the inside of them? or is that just a stupid idea?
thoughts anyone?

 

[Fred61]

Not entirely stupid but yes a waste of time. The box sections are designed to help with the heat loss as part of there rating they are also all sealed so the air can’t move therefore creating a heat stopping section. If you fill them you will effectively break that seel. Your other risk is you over fill them and the foam can distort the section. Fred