I built a CLC model over the winter on an enclosed but unheated porch, probably not different than your garage. I think heating epoxy to 140 F is a bit excessive for a cure for a home builder. You would have tears in your eyes if you tried to sit your bare ass on that temperature. The hotter epoxy gets the more it tends to run before setting up. I built a tent from a blue tarp and put a couple of 150 watt lamps under when the weather was cold. It is better to keep a uniform temperature so the epoxy all cures at the same rate. I kept the lamps a couple feet away from the epoxy. I don't think strength is an issue, but having some cured and some tacky is the same as being uncured if you get ready to resume work. Chemical reactions double in rate for each 20 F increase in temperature, so a little heat is a help. Good luck Jeff