Jim Rooney On The Level

Q. We had an addition put on our home in that extended our kitchen and added a sun room to the back of our house. Under the addition is a crawl space (I know your feelings about crawl spaces) that is only under the kitchen eating area. There is an open space under the enclosed porch. Would it be possible and practical to move our dryer vent from exiting the house to move the heated air under this crawl space to warm the floor and possibly reduce our heating bill? The space involved is about 12 feet by 15 feet and three feet deep. There is a flexible duct that extends through the crawl space to the rear wall to a floor register. There is no access to this space, only two vents on either end, one facing west the other east. The addition is on the south side of the house. Would this solve a problem or only create more than any possible benefits?

A. Now that our energy costs are going through the roof, I certainly understand why everyone wants to squeeze every tiny bit of value out of whatever they do when it comes to energy conservation. Some things make intuitive sense and heating up air hot enough to dry wet clothes in an enclosed tumbling drum-- a dryer-- then venting the heated air out of the house seems to many to be somewhat wasteful. Why not keep some of that heat? Pick up a load of laundry fresh from the washer and weigh it or just heft it to feel the weight. Dry it, then weigh it again. The difference in weight is the weight of the water the dryer removed. Remember a pint of water weighs a pound.

Home centers sell these little plastic boxes into which you put water to collect lint then hook the dryer hose to it. The theory is the hot-- now lint-free-- air will fill the laundry room with dryer heat and you get the proverbial two birds with one stone: dry clothes and free room heat. But the dryer air is very moist and there’s where the trouble can start.

There is a section in the building code that requires dryers to be vented to the exterior. Some may consider that chilly, vented, void space under your new room exterior space since it’s not heated or cooled and via the foundation vents is aerodynamically connected with the outside air. I’m not one of them. Exhaust vents designed to be vented to the exterior should do exactly that.

If you pump wash water heated to the point of vapor by the dryer into a cold space, much of it will condense back to liquid and cause all sorts of problems and some of which may not be immediately apparent. Not to mention depositing lint that gets past the dryer’s filter. I’ve seen crawl spaces where dryer vents have been directed and along with mold and mildew I see large quantities of lint. A nasty fire hazard. Even basements where the dryer vent has been leaking or not positively vented to the exterior the lint will build up on the wooden joists truly scares me. One spark and it’s blazing. You read about dryer fires regularly and the root cause is almost always lint.

Your crawl space should be insulated up under and between the floor joists. Peek in through one of those foundation vents to see. Your builder should have left an access to this area-- at least two concrete blocks tall and two blocks wide so someone, if they had to, could slither in there to do whatever may have to be done. Given the sequence of construction-- run the block foundation up then frame the addition-- insulation comes before finishes-- I wonder how the insulators got into that crawl space to insulate it. I’d double check that. You may have to provide access.

I don’t recommend running your dryer vent into that crawl space-- ever. If you want to use one of those little plastic interior vent boxes, promise you’ll only use it from November through March when the inside house air is bone dry and direct the moist dryer exhaust to the exterior the rest of the time. And don’t tell anybody I told you it was OK to do even that.

Keep the mail coming. If you've got a question, tip, or comment let me know. Write "On The Level," c/o The Capital, P.O. Box 3407, Annapolis, MD 21403 or e-mail me at jimrooney@jimrooneyonthelevel.com or inspektor@aol.com.