Outdoor air intake for dryer?

[bill allemann]

I was thinking of making a laundry room & door fairly airtight so an electric dryer would draw outside air and therefore save seemingly lots of energy. The basic ducting is not too complicated, but to avoid outside air chilling the room during the heating season, something needs to block cold air intrusion during idle time. A backdraft valve wouldn't work because it would be "pointed" the wrong way. Maybe if the outside air intake was low as feasible, and uninsulated ducting went up a cold wall above the ceiling, then did a U-turn and back down (insulated) a few feet to a laundry room ceiling register. I was thinking the inverted U would form a gravity type airlock of sorts. The suction of the dryer running would overcome the airlock, of course. This room isn't built yet, so access and space isn't a problem to install this type of stuff. Anybody done anything like this, or have any other ideas? Thanks Bill

[Joseph Meehan]

I believe there are some you can install either way.

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[m Ransley]

A fresh air intake will leave the dryer room alot hotter If its in a basement venting can be helpfull . But I can see times when your idea would be good, depending on outside weather. My using of laundry produces humidity which you may trap. and encourage mold in your washer A tight room will have drawbacks, in the summer especialy. In winter that extra humidity is needed.

[Joe Bobst]

If you do an energy balance on this notion you will see that it doesn't work unless you use electric heat in your home. If you are heating with oil/gas/whatever, then the energy used to raise a cf of air from outside ambient to inside temperature costs less than the equivalent electric heat from the dryer. One can raise a lot of other interesting if's,and;s, and but's, however the complications and cost of all the hardware leave the issue in doubt. If you think this is the way to save energy, put the dryer on your front porch like they do in Arkansas. Or in an unheated area of the house, like a garage.. Cheers.

Joe

[Joseph Meehan]

I would tend to believe that there will be some trade off, but not as much as you are thinking. The real issue is moisture not heat. We want to dry the laundry not warm it. So taking in cold, outside air and heating it, will produce some very dry air that can absorb even more moisture than the inside air, after it has been warmed to the same temperature. In almost all cases during the winter the inside air will have more moisture (likely lower humidity) than outside air, which if warmed to the same temperature as the inside air would have much lower humidity.

During the summer I would think Bill's idea would be even more cost effective.