Clothes drying in a tight well-insulated house
My wife Anne and I are in the design/planning process of a zone 4a 3 BR 2 bath 1900 sq ft one story slab on grade well-insulated (i. e. R40 walls) pretty tight (i. e. 1.0ACH50 or better) house, intending to be all-electric with a goal of using < 11,000 kWh/year for everything but automobile.
In that context, we are advised to plan on using a ventless clothes dryer, in order not to pour great quantities of conditioned air out and replace it with whatever leaks in, and not to have the extra vent penetration 24/7.
Initial shopping for this appliance, we don’t find much on the market; there are compact units that would be little use for larger items. Even these are pricey. A full-size Whirlpool model that lists for $2000 has garnered lots of negative reviews describing lint buildup in inaccessible places, which impairs the drying function.
So we asked a nearby net-zero homeowner how he has dealt with this issue. He owns the precursor of the above Whirlpool, it’s been trouble-free for 2+ years, but that may be because he mostly dries on a clothes horse. $2K seems a lot to spend on a dryer you mostly don’t use.
Could the following be done? Has anybody invented it? Or are the details just too daunting?
Connect a conventional electric dryer’s vent to the exhaust side of your HRV. When drying, switch the HRV exhaust side over to the dryer vent from the usual exhaust ducts. There would be the detail of arranging this so that the HRV would run balanced.
I think somewhere in GBA Martin has an item on the general theme “Simple is beautiful,” which the above scheme arguably violates.
Other solutions to this challenge, such as an affordable, trouble-free ventless dryer?
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Replies
Chuck,
Clothes dryer exhaust is full of lint, so you don't want that exhaust anywhere near the core of an HRV (for fear of clogging the core).
Have you read this article? "Alternatives to Clothes Dryers."
For a 2 bedroom small house over a garage we are doing now, we are putting the washer and dryer in unconditioned space in garage, with a small heater to prevent freeze up. This "garage" area is easily converted to living space so, we haved noted that future living space WILL CAUSE the same delima you have now.
In a recent build we built an extra bump out room AFTER exterior foam was completed. Has an exterior door in it AND an exterior door into house. that room has an inlet fan attached to dryer. ie turn dryer on the fan runs. Panasonic fans are pretty efficient.
Electric penalties YES!! solar fixed that on last one.
My own house, i have dealt with reg dryer penalty after bad experiences with ventless. 3 children is lots of clothes! Im hoping affordability and function come into range!
You could try a drying room. If you think about it, a heat pump dryer is just a dehumidifier with a fan and a rotating drum. You could put a fan and a standalone dehumidifier in a closet and hang your clothes there. It will take more space and take longer to dry without the drum but it will be cheaper to build.
People always say a dehumidifer is an energy hog but it's not true. In winter, a dehumidifer will heat your house with a COP well above 1. In summer, venting may look like the better option but the make-up air will be probably as humid as the one exhausted from your dryer and your AC will have to work harder to cool the room.
We've had a Whirlpool heat pump dryer for four years and it's been fine and trouble free. Your hrv idea sounds dubious. When considering costs, remember that the condensate from a heat pump dryer dumps into the same pipe as the washer, so you don't pay for cutting a hole in the wall, vent pipe, or any other installation.
Thanks to all who have responded.
One of the good things about GBA is that if you post "Clothes drying in a tight well-insulated house," right away a list of suggested GBA articles, including "Alternatives to Clothes Dryers," pops up. So I read that one and some others right away.
It's clear that lots of people have been very satisfied with their ventless dryer, and lots of others have been very dissatisfied. Good chance some day I'll be in one or the other of those groups.
I find circumstantial evidence that those who are happy with Whirlpool heat pump dryers tend to have older machines, maybe the predecessor of the model that is for sale now. Opposite to the way evolution is supposed to work!
Our plan includes a shared mechanical and laundry space. We have sized all rooms to be just big enough, taking that to be a fundamental green building principle. The drying closet sounds like a wonderful idea, but not sure we can squeeze it in without changing a lot of other things. If we decide to have a heat pump water heater (the mechanical/laundry room size is marginal for that too), so much for a drying space enhanced by waste heat from the water heater!
In the winter we hand-dry or clothes in the basement; why?
Because I weighed several loads of clothes coming out of our h-axis washer, determined that the average load contains about 4 pounds of water, and then setting the HRV in our basement on high (200 cfm; this HRV only services the basement because it is our radon mitigation system), calculated that the HRV easily handles that moisture load.
My wife thinks I am nuts but married 30 years this June so seems to work ok...
Peter