We need to insulate this direct vent gas fireplace properly before we seal it up. Im stressed beyond belief as an associate said if it is done wrong ,the mold you had will be back in a month without proper air sealing. I called a spray foam company to see how much it would cost to spray foam the top of the doghouse and the insides and i was told they cant charge anything less than $ 1000.00 i was shocked for only 40 sq.ft I live in Toronto and the winters are cold so i have to make sure this is properly done. Besides spray home which i clearly cant afford for a small area, are there any suggestions to seal this for the e.g the brick area, the plywood, thankyou.