I have not tested this yet but I like it just the same. Went and spent $25 for a piece of 1/4" plexi glass and had it cut to the size of the screen. Added the metal springs on the edge to keep it tight, weather stripping and a couple of knobs to old onto to put it in and take it out.
Cut hole to line up with my inside wood and pipe cover and added some weather strip on the back of the wood around the the hole. Now when I put the inside panel in place, there is no cold air coming in around it (bringing fumes as well) Once installed I have to go outside

and install a section of vent pipe to carry fumes out away from the house to help prevent them finding their way back in. One last adjustment I may do is change the inside filter form the pleated type to the open mesh fiberglass type to allow for better air flow.. fan may get painted but who cares!
Oh I glued another piece of thin plexiglass over the piece I cut out and the window holds that in tight when it is closed..
Can you say OVER ENGINEERED!
