I think it will work fine as long as the air from the attic circulates back down to the shop. Just put either a regular floor vent in the ceiling or one that has louvers that open when under vaccuum/pressure. I have a DC on the first floor of my garage and the shop is on the second. There's a door at the top of the stairs going in to the shop. I haven't yet, but am planning to put a louvered vent in the bottom of the door. That way, when all doors are closed and the DC is on, the air that gets sucked out of the shop will get replaced by air blowing out of the DC by coming up the stairs and through the vent on the door. The minor problem is heat/air conditioning. Oh well. I can't have everything. Luckily, I live in a mild area that doesn't require a whole lot of either. If you don't have a way for air to circulate when the DC is on, it won't be as efficient, and you may burn the DC motor up depending on how tight everything is. If you allow the DC to expel air out the roof, then you will lose ALL your heat/ac. Plus, you will need to let air IN somehow and somewhere else. At least with my set up, I keep most of it. Even though I lose some to the first floor, at least it stays in the garage and doesn't get lost outside.
"Veggie burgers aren't bad if you put enough meat on them"
Last edited by TS3660; 10-19-2010 at 10:28 AM.