Hi, I think you would have to use the rope type seal as this fire proof sealant product cures to a hard fire cement type seal, I do not think it would give any flexibility with the different expansion experienced between glass and steel, in my opinion, a good seal could not be maintained. In my window fitting experience I found that silicone (building type) has a "melting point" after which it shrinks then bursts into flame, probably not the effect you are looking for. Regards.