 so you need to have a makeup air situation there now if you've got an older house that is pretty pretty passive as far as letting air in and out that's not well insulated that's a whole different story it's going to pull it out of the crawl space it's going to pull it out of wherever those leaks are in the home but makeup areas you get that house tightened up is going to be very important so you can put that new air back in and then you're not grabbing dirty air if you do this it's going to get filtered it's going to run through your system so it's going to be clean air coming in