I am getting two quotes for sealing the metal air ducts in our basement. The goal is to reduce air leakage and save $ on a/c.
#1 says he uses foil tape (which has the sealant on it) because it is faster to install and doesn't crack like mastic "paint" would- his example was the return air handler metal does flex a bit. He also said he will use the tape to seal around supply and returns on main living area.
#2 says he uses mastic because it seals better; he will use spray foam to spray from the basement around the supply and return areas. He is also giving quote to air seal the plate/sills around basement perimeter against air filtration.
Any input re using the two materials? What about method of sealing air supply and returns- at main level with tape or from below with foam? The only place I can see where the movement of metal might cause a crack would be just at the air handler unit. Maybe it really doesn't matter-just personal contractor preference? I have 1 quote and am waiting for 2nd one.
One more question. I have a hot water heater in basement and the #2 contractor noticed the vent going into the pipe was undersized for the water heater size. It is 3" but should be 4" he said. The vent isn't drafting all that well if the bathroom fan on the main floor is on, all doors shut, and he said this should help.
Thanks for the input. I'll probably be deciding in the next week or two which one to use, and get on with it.