didn't read any of the reply's so my bad if this had been answered, if you want to air seal it you can go about this 2 ways, go to a local hardware store and by a large role of plastic and some tuck tape- not duck tape, tuck tape is red and 15-20 $ a role, you basically cover the entire room with this plastic and then you tuck tape as the seal.- carpenters that build houses use this technique. or a much less expensive but can be messy if you don't keep a steady hand is buy some silicone spray seal, its 15-20$ a can. you only need 1 can, this stuff comes out as foam and needs several hours to dry but it will air seal it 100%