Venting a dryer into open crawl, with snow pack
evergreencertified
| Posted in General Questions on
Hi all-
We’re renovating a 1960s ski house located on a ski mountain in WA state. The building has a partially open crawl (on the downhill side) and I’m wondering if anyone sees an issue with venting our dryer into that space. The snow pack in winter is significant. There should be a melted gap between the snow and the house but my worry is that there might not be a lot of airflow through the open crawl in the winter. Lots of warm humid air in a cold environment makes me nervous but maybe I’m being paranoid …?
thanks!
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I think you would have fewer worries and actual issues if you switched to a heat-pump drier. This article is not directly related to your question, but I think it will help you to decide on a course of action.
https://www.greenbuildingadvisor.com/blogs/dept/qa-spotlight/how-vent-dryer
Thanks Steve, read that this morning and I am definitely considering the heat pump option. We'll have a gaggle of adults and kids up there skiing in the winter though, so being able to quickly dry things is important and I hear the heat pumps take longer.
Sean,
No, you don't want to terminate your clothes dryer vent in a crawl space, even if the crawl space is "partially open." Extend the duct to an exterior wall.
I agree with Martin, run it to an exterior wall. If that's otherwise difficult, it can run through the crawlspace to the exterior.
Most heat pump dryers have a range of modes that let you prioritize fast drying vs. energy efficiency. The specifics of how fast the fast mode is vary by model, but some get close to the speed of a conventional dryer. On the other hand, if his is an occasional use house, it might not be used enough in total over a year to justify the investment.
I know what an unvented space is and I may go that way one day but I do not have the time currently to do that as it is a bigger job. My crawlspace is attached to a storage area in my garage. I would have to somehow block that off, as well as block the vents, insulate the walls, like I said a much bigger job that I may do one day but am behind on projects right now. My intention is to just replace the damaged duct and the duct where there is a moisture problem. Plus, I have read conflicting information on radon in a vented vs unvented space. (Not trying to start a debate).
If you run the vent through the crawlspace then you need to insulate it. Water will condense inside the vent. The wet pipe will then collect lint and hold more moisture. I have literately squeezed water out of a hand full of lint pulled from a dryer vent. Use only rigid metal 4 in duct. Also use only metal 90 degree elbows. The elbows will adjust to other angles to help line it up. Standard 4 in metal air vent is what we use. We get the premade insulation the fits over the pipe. Do not screw the pipe together as it is against code and the screws will collect lint and cause a clog. Use metal foil tape made for HVAC ducts...dont use the so called grey duct tape.
If possible run the vent the same direction as the floor joists. This way you can tuck the vent up between the joists and its is easier to go out the band joist.
And pitch the duct so it can drain any moisture to the exterior.
You dont want any water collecting in the vent. When the pipe is runs through an unheated crawl space in snow country there is a good chance the pipe will be cold enough to condense. There is a lot of fine lint that passes the filter and condensation will grab that lint. So you want to avoid the initial buildup.
What you want it the pipe to stay warm enough that all moisture passes through the vent as vapor.
In terms of what you can get away with on renovations, the local climate really matters. A vented crawl space isn't always a great idea either, from total energy use point of view (though for most of WA it's OK from a moisture point of view, as long as you aren't venting a dryer,kitchen or bath exhaust into that space.)
What is the elevation (or nearest ski area), to get a handle on the actual climate?
Is it on the western or eastern side of the pass, or somewhere in the middle?
Thanks everyone, good points on condensation inside the duct. I plan to just figure out a way to run it within the envelope to an exterior wall. Wires and pipes be damned! Any heat lost through the pipe will be bonus space heat anyway.
thanks!
Anywhere above the snow line in the Cascades turning the crawlspace into conditioned utility-chase space by sealing off the outdoor vents, installing a ground vapor barrier and insulating the foundation & exterior walls is almost certainly going to be worthwhile from a heating energy use point of view, no matter how well insulated and air sealed you think the floor is. The conditioned crawlspace should give you plenty of room for running dryer duct.
Pay attention to code maximum duct lengths, including the "equivalent lenght" of all the ells. Hard--piped (not flex) and as straight as possible is key to getting better flow (== more efficient drying) and less lint build-up (==fire hazard) inside the ducts.