Should we get a dehumidifier or do something else?

October 26, 2011 12:57 PM

Is a dehumidifier the right solution for my problem? What else should we be considering?

We are on the verge of buying a dehumidifier, and I want to make sure that we're doing the right thing.

Our house was built in 1943. We live in Portland, Oregon. The house has three-year-old double-paned windows. The main floor of the house is fine -- a little dampness when we take a shower or do water-heavy things in the kitchen, but we've ameliorated that by running the bathroom fan to the outside and installing a high-powered kitchen fan that also goes outside. We used to have occasional mold/mildew (on books and a stuffed animal) in the bedroom next to the bathroom, but none has grown since we installed the fans, which we're vigilant about using.

The basement is a basement. It's got some water problems, which we're in the middle of fixing. These are from plumbing leaks and a poorly-sealed window.

The finished attic is a problem. Whenever someone takes a shower, moisture collects on the walls. Until today, when we turned the furnace up and opened a window briefly, the windows had been collecting condensation for about a week. Anything organic up against the walls has grown little bits of mold -- today, I found that the leather soles of my husband's formal shoes were gray and fuzzy. The attic is one room, the length of the house and about 3/4 its width, with one heater vent in the floor. Last year, my husband re-did all of the insulation in the portions of the attic that he could access (side walls, not the ceiling). Even so, the room is always colder than the rest of the house, and gets more damp during the humid winters.

It's the master bedroom -- literally all the other bedrooms are full, as in the last year, we've had a baby and gained two housemates. My husband and the baby and I all sleep upstairs. None of us have noticed increased respiratory problems, except that I get sneezy when I clean (I'm allergic to dust and mold).

We are planning to add more roof vents to the house -- we think it's probably underventilated -- and we're considering buying a dehumidifier. What else should we be considering?

Note: we're a single-income household with several other major ongoing house projects and a depletion in savings from having had a baby. We want to do what is right for our family, and we have very limited funds with which to do that. I'm looking for the solution that has the best combination of effective and economical.

posted by linettasky to home & garden (5 answers total)

Have you changed the filter in your forced-air furnace recently?
posted by mhoye at 1:39 PM on October 26, 2011

Have you used a hygrometer in the room to measure the humidity level? You can buy one pretty inexpensively on Amazon or probably at a hardware store. I assume you have a moisture problem, but at least you'll know how bad it is and how well your solutions are working.

We have a REALLY damp house. Humidity is usually between 70-80%, higher on humid days. A dehumidifier has worked well for us and really cut down on the mold growth. Our landlords installed in-wall AC-dehumidifier units that we use in the summer, and we use a free-standing dehumidifier in the winter. The freestanding units push out a lot of heat, which is nice in the winter, but way too hot in the summer (especially if you're using it in the attic!) So if you anticipate using the dehumidifier in the summer, you should think now about whether you'll be able to vent it out a window. Some models have vent hoses and some don't.

I'm not sure what's causing of your dampness, but a good dehumidifier will keep the dampness and mold way down. It's a pretty easy and cheap solution until you can do some bigger picture work, if you choose to.
posted by robinpME at 1:42 PM on October 26, 2011 [1 favorite]

In one older Seattle house I lived in, the bathroom ceiling fan vented into the attic, not outside, and I wondered at the time if lazy renovators were reluctant to do everything necessary to pierce the roof in such a rainy climate.

So check that out, and make sure that, if the bath is vented to the outside it isn't leaking air into the attic anyway, because only a small amount of moist air from the bath would ever reach the attic if the fan system is working properly.
posted by jamjam at 2:29 PM on October 26, 2011

Or, your house could be so tight the fan can't suck the air out of the bathroom, and the hot, moist air rises through the heater vent into the attic.

In that case, look into an air-to-air heat exchange vent to be used in conjunction with the fans in the bath and kitchen.
posted by jamjam at 2:39 PM on October 26, 2011

These are all good ideas. The furnace was replaced in June, and hasn't been run until just this week, but I'll keep the filter thing in mind. With regard to the bathroom fan, it definitely vents outside -- we made it do that. But the overall tightness of the house is something to take into consideration.

Thanks, robinpME -- I think we'll definitely get a dehumidifier. We've been talking about it for several years, so it can't hurt.
posted by linettasky at 3:30 PM on October 26, 2011