Hi,If we have a high efficiency furnace that is getting fresh air from the oustide, would there be any use for an air to air heat exchanger?Thanks in advance.
There may be certain times when one is necessary, especially if one puts an indoor hot tub to heavy use, but in general, no. Indoor air quality seems to be receiving as lot of attention these days, but it's mostly marketing hype. If you have a 4 round duct that connects from the outdoors to your return air ductwork that should be sufficient to introduce some fresh air into your home. This fresh air duct should not be confused with the PVC pipe(s) that are connected to the furnace itself. Some high efficiency furnaces have a PVC pipe carrying smoke to the outdoors. They may also have a PVC pipe that brings combustion air into the furnace burners. These PVC pipes are 2 or 3 and have nothing to do with bringing fresh air into the living spaces.
Right - after we got all our houses sealed-up with tight windows and insulation, some houses don't breathe enough. An air exchanger (that introduces outside air without bring in cold or letting out heat) can be added to your system or can be a stand-alone unit. But they aren't cheap. We just had a simple duct added to introduce outside air into the cold-air return ducts.......with a damper we can open and close. By design (and verified when tech tested it) it introduces up to 5% fresh air when the furnace blower is on. Depends on your climate: we decided it isn't a consideration for us in hot weather.........and not a significant factor in winter as long as temps are over 20 degrees F - below that we close it. Cost less than $100 to have the duct installed.
No it is a waste of money. They are for homes that have very very tight seales on doors and windows where outside air is not getting in anywhere
