plant roots need oxygen. they do not use CO2. although some mature forest trees do uptake CO2, cannabis does not. if you are growing soil i dont see how you could possibly vent into the rootzone. you must mean hydro, in which case: the water temperature for hydor must be in the mid 60's. i dont see how venting hot air from the growroom into your root container is going to help.
not sure i see a viable experiment here.