I am installing a switch & light, and need to run electical wire from the light switch, up the wall, then through the roof to the light fixture. My question is, at the top of the wall the electrical wire will come close to a heating vent (within 2 inches, for about 3" of wire). Is this ok? Should I put some insulation between the two? They won't be touching, I just want to make sure it is ok though.