from Leland in Boulder, CO:
#747
I heat my home primarily with a wood stove. To reduce our heating demands, I've considered a heat-recovery unit on the dryer exhaust to preheat air coming into the dryer (I'm sure this would require some crafty engineering to seal the dryer intake). Do these kinds of devices work and would it be worth the effort? We use the clothesline outside when we can. One reason I thought of that is that as I go around sealing doors and windows, etc. I reduce the makeup air flow for the wood stove. It sometimes back drafts when we turn on the dryer if the fire isn't hot enough in the stove to maintain the draft. This would at least isolate the pressure drop from the dryer exhaust.
It may be more trouble than it's worth.
I hate to crush ingenuity but heat recovery on a dryer may be more trouble than it's worth. Effective heat recovery relies on several factors including a balanced air flow between the incoming (intake) air and the outgoing (exhaust) air, a good medium for transferring heat from the air stream, and sufficient contact area between the air stream and the medium to transfer heat. With a dryer it will be difficult to get the volume of the air streams to be equal (you would need a fan on the intake air stream to match the volume of the dryer exhaust fan because the resistance of the added duct work may reduce the overall airflow of the dryer, which will decrease the effectiveness of the dryer) and the exhaust air will likely plug or reduce the effectiveness of the transfer medium with lint. There are safety factors to consider as well. The unit may present an increased potential for a fire if the lint starts building up.
Indoor vent kits cannot be used with a gas dryer and could cause other problems in the home due to moisture, chemicals, and lint in the dryer.
An easier solution to back drafting is a through-the-wall vent that you open when using the dryer. Look for one that can be adjusted or closed, has an insect screen, and if possible, a filter. There is no recovery of the heat but heat loss from the infiltrating air will be minimized with proper use.
Published Monday, March 15, 2010