Are you sending conditioned air outside? I set my system up 20 yrs ago when I started woodworking and am evolving into pool cues. My dust collector is located in a small insulated room in an unheated area of my building. I have a 20 in. x 20 in. opening back into the shop covered with a funace filter. Theory at the time was to avoid sending $ out the wall. Option A = installing hepa type filter on both sides of opening. Option B = eliminate opening. Anyone doing this?