Air exchange question - whole house fan or dehumidifier system?

theresasJune 4, 2011


I hope some of you will have some advice for me. We have humidity and smell issues with our basement (moisture activates litter pan smell, gag) and I'd like to be able to draw out warm air at night and replace it with cool evening air, thus avoiding AC at night.

Originally I thought the only option was a whole house ventilator, installed in the ceiling, vented into the attic. I wondered about keeping the main floor's windows closed and opening basement windows and the door. We do have a rather large, open stairwell going to the basement. Then I ran across dehumidifier systems, not just our little stand-alone plug in NOISY sucker. One of them ( seems to be a dehumidifier and whole house air exchanger all in one, but the air is sucked out from the basement, bringing the main level's air down there, then out.

So will it make my basement really warm, or just slightly warmer? It's a refuge from the heat in the summer, for as long as our noses can take it. I'd also like to be able to stop dumping tons of baking soda all over to soak up nasty smells. I think it would help considerably with the shockingly cold air we have down there in winter, rendering the basement useless to us.

I think adding a permanent dehumidifier will be good year-round, no more damp air in summer, no more ice on windows in winter. But is putting the combo unit with an air exchanger down there a bad idea versus putting it in the ceiling on our ground floor?

We have only the ground floor and the basement, no second story, if that helps.

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Whatever you get, you definitely don't want to vent that moisture into your attic.

I've heard of this system. Haven't investigated it. You might find it interesting:


    Bookmark   June 4, 2011 at 5:09PM
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The device sold via that web site you posted looks like it is just a little fan. It will suck air into your cellar from the least resistant pathway. You only want to suck outdoor air into your basement if the dew point it is above the temperature in your cellar. If the air being drawn in is too humid, you can make the problem much worse. It will be like water condensing on a cold beverage container.

Dehumidifiers will warm the air. More efficient ones do it less than cheap ones. I would search further than the ezbreathe.

What kind of heat do you have in your house? Is the main floor insulated?

    Bookmark   June 5, 2011 at 5:24PM
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We have central gas heat and central electric air and the main floor is insulated, ceiling and walls. We do not have insulation between the floor joists in the basement. I've seen some people do that and I believe it is a less than stellar idea.

I talked with the EZbreathe guy and yes, it does sound like a fan that will just suck up air out of the main floor, take it down to the basement to help dry it out or just circulate air, I really don't know what he was getting at, then expel it through a 6" hole that would be covered with a dryer vent. Low energy cost, $2-4/month, so yeah, just an efficient fan.

I don't want the warm air from upstairs pulled into the basement in the summer. I like it cold in the summer. As it is, we run a fan at the bottom of the stairwell blowing cool air up to our living room (rather large, very open stairwell).

I would like to keep the basement warmer in the winter. The vents need to be rebalanced or something. We don't get a good flow of air on the main floor unless I partially shut the 3 downstairs vents. It wasn't always like that--something seems to be up with our blower motor I'm guessing.

Venting into the attic does seem a little backwards now that you mention that, V.

Maybe a fan in one basement window blowing air in and one in the another window sucking air out will help a bit? We do that in the summer with the upper floors, one of those 2-fan window fans on one side of the house and another across from it. I've thought more than once about putting a screen door up in the walkout for some serious ventilation.

Right now money is a huge concern, so anything I can do that won't be $2300 (EZbreathe) that will be effective and safe is going to win the prize with our house.

    Bookmark   June 6, 2011 at 9:38AM
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Your basement smell is a symptom of too much moisture in your basement. When air with a high dew point gets into your basement, some of the water vapor in the air will condense allowing molds, mildew, fungi, and other organic organisms to flourish. This causes the bad smells.

First, if you have liquid water entering your basement, stop it. You can not have a dry comfortable basement if rain water or ground water are getting in. I'll assume that you do not have liquid water getting into your basement.

If you live in an arid climate with low outdoor dew points, you can ventilate your basement/home with fresh, low dew point air from outside to solve your issue. In an arid climate the ventilating fan will solve your problem, but you can perform the same function using different equipment for less. The dew point of the outdoor air must be lower than the temperature of your basement walls and floor for this to work.

If you live in a climate with green grass outside your home, the outdoor dew points will be too high (at least part of the year) to ventilate and dry your basement and you may exacerbate your problem using the ventilation fan contraption.

Assuming you live in a green grass climate, minimizing fresh air infiltration and a basement dehumidifier are the best solution to making your basement comfortable and healthy. Find any openings where air can enter your basement (check where wood and cement meet and around windows and doors)and close them with foam insulation or caulk. Check out energy star dehumidifier ratings to find models that are cost effective to operate. If your basement has a drain, some dehumidifiers will drain themselves eliminating the bucket dumping chore. The Santa-Fe compact is a great dehumidifier that is energy star listed and less than half the cost of the ventillator.

Here is a link that might be useful: Santa-Fe Compact dehumidifier

    Bookmark   June 6, 2011 at 4:14PM
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I second the post from dry dog. I had to install a Sante Fe unit into our new home to get rid the the very smell you mentioned.

The problem is that with a tight house and a basement that is 3/4 below grade, the moisture coming through the foundation walls and concrete floors has no place to go. We noticed the problem on days when the humidity was very high outside but the temps were too low for the Ac to come on. I bought a humidistat and measured the basement humidity was abobe 70% on some days which is not good. Started to notice wet spots on the concrete floor and the musty smell.

For a short term fix I just ran the AC way below the set point and presto - smell and spots went away. I then ordered the Sante Fe unit and that has been a great permanent solution. I bought mine from If you get one of these, you will need a drain because it sucks out a lot of water. I installed mine of top of 4" solid conderblocks to elevate it for drainage and the drain dumps into the sump pump basin.

The air output directlty in front of the Sante Fe output vent feels dry and warm but once the basement gets down to a decent humidity - say 50% - it actually feels cool and crisp.

You can hook up your DH in a variety of ways. I chose the standalone configuration which sucks air from one side of the basement and dumps it at the other end. I then use my HVAC fans to circulate air from the basement to the rest of the house and back. My HVAC unit is in the basement, and there are large air intake vents in the basement and upstairs that feed the main input duct so I get good air circulation between the floors.

I bought an IAQ thermostat (Honeywell Vision Pro) that allows me to program the HVAC system fan to turn on for up to 20 minutes every hour to circulate the air even if the HVAC is not running for AC or heat.

The Vision Pro also has it's own built in humidistat and can be programmed to use the AC as a dehumidifier if the humidity detected at the tstat is above a programmable amount. The combination of the two features - the whole house DH in the basement and the ability to automatically run the AC below the set point when humidity is too high upstairs - has been a terrific solution to our moisture problems.

One thing to note - my Sante Fe unit has an anolog knob for setting the humidity level (no digital output). To get the humidity just right in the basement, I used a battery operated humidistat and kept adjusting the knob until I found the spot where it would keep the basement at a 50% humidity level.

I also have a separate Energy Recovery Vent system in my house which I use to bring fresh air in and exhiust stale air from the house. I am very careful with this unit and only turn it on when the humidity outside is low because I don't want to suck in fresh moist air. That would only make the Sante Fe unit run more. I learned that through trial and error - mostly error.

If I were in your shoes, i would first fix the humidity issue with a whole house DH. Put one in the basement and then manually turn on the HVAC fan when you want to circulate air between floors. If you get tired on the manual switching of the fan ON, you can add a tstat that provides an automatic air circ feature.

After that, then decide if you want to add a seperate air ventilation system in. These are recommended for very tightly sealed houses. If the house is older, you may get enough air infiltration through the walls already.

You can fix your issue for a lot less than 2300 dollars. I think the Sante Fe runs around 1100 or so but deals can be found. BTW - don't go cheap on the DH unit becuase you really get what you pay for with these things. Do searches and read reviews. Check the specs and see how many pints of water per 24 hours the thing is rated to extract. Check the air flow rate (usually a CFM number) to see how much air it pushes. Beware of systems that don't have a drain (they use a pan instead) unless you plan on dumping the pan every day or more depending on your humidity problem.

Good luck.

    Bookmark   June 7, 2011 at 9:35AM
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Sniffdog means hygrometer instead of humidistat when it comes to measuring humidity. The humidistat controls equipment.

Those inexpensive electronic hygrometers generally work well, but they can be inaccurate and become inaccurate. I check mine with a sling psychrometer every now and again.

    Bookmark   June 7, 2011 at 5:01PM
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I have the thermostat ordered, ours is pretty "meh" and I love the idea of letting it control the humidity too (I got the right model for that feature).

Tonight I hope to run to the store and get two hygrometers and see what it's like upstairs and what it's like downstairs with the humidity levels. It probably doesn't help that I like to keep the windows open whenever possible. It's cool outside in Chicagoland, but I still think it's humid. It doesn't feel dry.

    Bookmark   June 23, 2011 at 11:11AM
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