Humidex or other basement ventilation system?

The Metal PeddlerAugust 3, 2006

I need to improve the air quality in our basement & am trying to research various options. I want to be able to exhaust out the stale air and bring in clean fresh air without greatly affected our winter heating bills.

I have been looking at Humidex systems but cannot find any independent reviews of them & am loathe to spend hundreds if it doesn't do much more than a regular fan.

Does anyone have any experience or other suggestions? The basement is about 900 sq feet with 6 tiny windows and an outside door.

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The Metal Peddler

I managed to find some Humidex discussions on BobVila forums, but they were very mixed reviews. Given they are so expensive, I might stick with window fans instead. Now..... there are so many window fans on the market, how the heck do you choose one? Exhaust type only, reversible or twin type?

    Bookmark   August 3, 2006 at 12:40PM
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I too considered Humidex, EZ Breathe, and Musty Basement Solution. I studied their web sites, read everything I could find on line, and had a MBS rep come to the house. Please allow me to share what I've learned...

They work by venting cool basement air and drawing warmer air from upstairs. The relative humidity of the warmer air is lower than the cool basement air and hence dryer. Their system consists of an exhaust fan in the basement and a wall or floor register to allow air flow from upstairs to downstairs. It seems to me any exhaust fan in the basement along with a register or open stairwell will serve the same purpose.

All their websites make the erroneous claim that moist air is heavier than dry air. This, of course, isn't true and is a common misconception. Ask any meteorologist why a barometer falls as the amount of water in the atmosphere increases.

All their websites infer that the system works by drawing dryer air from upstairs and replaces the moist air that has "settled" in the basement. In fact, the warm air pulled downstairs will lower the relative humidity (because of the rise in temp, not because the moist air settles to the basement floor).

One major problem with the system is that as air get pulled downstairs, it must come from someplace and that someplace is most likely unconditioned outside air pulled in through cracks and leaks in the house. If the outside air is muggy, the system won't help.

    Bookmark   August 3, 2006 at 4:24PM
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The Metal Peddler

Thanks, That's pretty much confirmed what I thought. We ended up just getting a $20 window fan & running the dehumidifiers constantly for now. Not ideal but I'd rather pay a little more in bills to have cleaner air! I'm still looking for a more permanent or suitable alternative though

    Bookmark   August 11, 2006 at 11:59AM
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In practice, condensation will occur first over the lower part of the window because the glass surface temperatures are not uniform, being lower at the bottom than at the top. Condensation at the base of the window and also at the sides tends to be more severe with metal or aluminium sashes and with some special units such as factory sealed double-glazing where the method of assembly results in increased heat transfer at the edges. Drapes or other window coverings can contribute to the problem by restricting the flow of warm room air over the glass surface.
The homeowner need not measure the humidity directly; he/she can simply use the windows as a guide to the proper humidity level within the house. As soon as the objectionable condensation occurs on the inside surface of the window, steps should be taken to reduce the relative humidity by controlling the moisture sources and by increasing ventilation. Condensation is just a barometer of the in-door air quality of our homes.
It is a common belief that for health reasons there should be a lot of moisture in the air during the winter months. There is no evidence that either the health or the comfort of people will be adversely affected if humidity is kept at a level that will prevent excessive condensation. There is, however, an increasing range of research that clearly points to the fact that high moisture levels are not only bad for our health but also the well being of our homes and household environment. Comfort and nasal dryness will be noticeably affected if the percent of relative humidity drops excessively low. This is not normally the case in New Zealand.

One way that heat is transferred through air is by convection. Convection of heat energy in the atmosphere involves the movement of air. Air is a poor conductor of energy, so convection is a major process of energy movement in the Earths atmosphere. In the atmosphere, convection occurs when a shallow layer of air in contact with a hot surface warms by conduction, acquires buoyancy (warmer air is less dense than colder air), and rises, taking with it the energy that it stores. As the Earth is heated by the Sun, bubbles of hot air called thermals rise upward from the warm surface.

In meteorology, convection refers primarily to atmospheric motions in the vertical direction. The term "advection" is sometimes used to refer to air motion in the horizontal direction. An air parcel will rise naturally if the air within the parcel is warmer than the surrounding air (like a hot air balloon). Therefore, if cool air is present aloft with warm air at lower levels, thermals can rise to great heights before losing their buoyancy.

Such convection processes in a large part dominate the world's weather, including the production of rain and snow, thunderstorms, hurricanes and frontal systems. When air convects it cools. If cooling is sufficient, the temperature of the rising air will fall below its dew point, releasing excess water vapour as clouds and ultimately precipitation.

    Bookmark   June 27, 2007 at 8:58AM
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"I need to improve the air quality in our basement"

If this means you're smelling mould and mildew, the better option would be to eliminate the source of moisture that's feeding it.

Opening windows in the summer just brings in more humid air that needs to be dehumidified.

    Bookmark   July 8, 2007 at 11:10AM
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I built an air ventilator from parts (high mtbf 20yr continuous flow vortex fan prewired, 120v dehumidistat, and router variable speed controller) found on ebay all for under $200. At the home depot I obtain a aluminum dry vent kit and built a wood platform for the ventilator fan to sit and accommodate speed/dehumidistat control units.
The fan situated close to the floor along with the controls near a window located farthest away from the furnace. Set the dehumidistat and fan speed and that is it. Takes up

    Bookmark   January 22, 2009 at 1:09PM
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In a home I sold a couple years ago, I had an EZ-breathe system. I did not notice any significant change in utility bills.

I am now looking to buy a new similar unit that I can install myself to save on installation cost's.

In response to previous comments about basement humidity, think about this. If you have a dry, leak free basement, then why does it smell musty? ....CONDENSATION.... You will have condensation against the cool concrete floor and low on the walls. Replacing this air with any fresh air source (weather heated, cooled or from outside) will eliminate the stagnant musty air. If you ventilate the air from the top of the basement and not at the floor, the air at the bottom will remain undisturbed and as the condensation evaporates, the air will fill up with this humidified air. It is logical if you just think about it.

If anyone knows where I can get an aftermarket, DIY install unit, please e-mail me. Thanks.

    Bookmark   July 16, 2009 at 2:14PM
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An earlier post says that the air from upstairs is lower relative humidity. Highly likely to be a true statement- but incomplete. Bringing that air to the (probably) cooler basement will increase the relative humidity of that air due to the temperature change alone. My suggestion is to keep the basement closed up and use a dehumidifier.

    Bookmark   July 20, 2009 at 3:21PM
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Comparing EZ-breathe and waveventilation, which one is better or basement ventilation?

    Bookmark   July 30, 2009 at 12:01AM
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Replacing this air with any fresh air source (weather heated, cooled or from outside) will eliminate the stagnant musty air.

It's not "stagnant" air that creates a musty smell. It's damp air that feeds mould that smells. And bringing in "fresh air" to a basement in the summer only makes the problem worse.

As Lstiburek says in "Finishing Basements", the first linked document below,

"Once the basement is finished, try to keep the relative
humidity to a comfortable level. This generally
means keeping the basement windows closed and
running a dehumidifier or an air conditioner during
the humid, summer months. If a musty odor is
detected, the tendency is to open the windows to
"air-out" the basement. This should only be done
if the outside air is drier than the basement air."

I have yet to see how all these expensive air-exchange systems are any improvement over a simple stand-alone dehumidifier.

    Bookmark   July 31, 2009 at 6:15PM
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I have a mildewy finished basement with wall to ceiling enclosed bookcases which sits upon about 235 square feet of floor. I pulled a rug 30 years ago that was glued to the cement and covered it with a good quality rug that had a pad and have now pulled that as well. The mold on the back of the rug contributed to my inability to utilize the basement. During the summer I run a humidifier and open the three small windows down there. And there is a half bath as well. Anyway, I cannot stand the mildew anymore and have done the following: wiped down the walls and painted with Behr mold resistant paint...sanded (as best we could) the cement. I will be putting in a Tjernlund double modular 180 cfm fan with humidastat between the ceiling joists, putting a thin layer of cement over the existing cement-then applying Armor seal tred plex epoxy resin paint/flooring. I cannot afford to dig a trench around my house (we are built on clay) but will install gutters on all sides that I can. Does all of this sound rational? Is there more that i could do? I would like to install a humidex or ezbreathe fan but they are very expensive. I am not certain if the hype about moisture needing to be drawn from the floor up and out of the house makes sense. The Tjernlund is at the top of the room and is vented out. Suggestions?????

    Bookmark   April 2, 2010 at 5:53PM
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During the summer I run a humidifier and open the three small windows down there.

First, you need a dehumidifier, not a humidifier. A humidifier puts water into the air--sometimes useful in dry winter months. A dehumidifier takes water out of the air, essential during warm months in most climates.

Secondly, you must keep the windows closed during humid months. Otherwise, the dehumidifier is useless. Whatever water it is taking out of the air is more than being replaced by the "fresh" air that your open windows are letting back in.

Thirdly, a carpet with an underpad is about the worst finishing you can put directly on a concrete basement floor. (Roll vinyl and vinyl tiles come a close second.) This is because of the typical moisture drive into the basement during summer months. Your carpet pad is trapping that moisture between itself and the floor. If you insist on carpet, either put in a proper subfloor system or only glue down a low pile synthetic carpet with a moisture resistant backing.

Running an exhaust fan from the basement while keeping windows open does nothing but circulate more damp air into your basement. The only exhaust fan you should have in the basement is above any stove or in a bathroom, or if you wash and regularly hang clothes to dry in the basement, in that area.

    Bookmark   April 2, 2010 at 6:42PM
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I'm sorry I typed the wrong word...I have been running a powerful dehumidifier for years in the basement. I have removed all rugs and would never put another in that basement. My concern is will the epoxy resin paint for the cement help to control the moisture and would the dual fan 180cfm's which can be switched to intake and outtake with a moisture control humidistat be as good as the Humidex or the ezbreathe fan? I don't know enough about epoxy paint and would love some advice.

    Bookmark   April 2, 2010 at 10:45PM
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Learned quite a bit from this discussion.
Well worth searching previous posts!

Living in New England and with this humid stretch we're going through, the smell has come back...

My source is condensation from the water treatment system I've put in, which of course is at the well inlet to the house.
Drip, drip, drip all day long..

I have set up a in-line fan through 4" dryer vent line (run outside), so have the exhaust I need.
Yet was concerned about my in-take air.
Just makes no sense to be drawing outside humid air..
Thank you for confirming!
Moving air alone is not the solution.
It must be drier than the air being replaced.

I'm about to add a floor grate to draw the conditioned air into the basement until the air dries out a bit 'round here.
Then back to opening the basement windows.

Please let me know if I mis-understood anything here.
Hate to cut a hole in floor for nothing....
Been there, done that and wifey still reminds me..

    Bookmark   July 19, 2010 at 4:22PM
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I went on a trip from the prairies to the Maritimes this year. I have asthma. No problem on the dry prairies normally, but not good news in the moist Maritimes. By the end of our 3 week trip I was having trouble breathing.

My sister has a Humidex system in her basement. Whenever I had difficulty breathing I went to that area of her house and immediately perked up. Breathing was a LOT easier there. I'm sold on these things! For $1200, I'd do it just for the health benefits for me...if I lived in the Maritimes. Which I don't. But definitely worth thinking about as we are looking at retiring in the East.

    Bookmark   July 18, 2011 at 12:32AM
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i live in the maritimes and we purchased a humidex this yr in got rid of the musty smell,i have allergies and it seems since we put it in i have had a presistant cough that i can't get rid of ,i have been looking on the web to see if anyone else has had problems and we did not pay 1200. it only cost alittle over 500.and it is not a pony 1 for crawl spaces it is a bigger 1.

    Bookmark   December 17, 2011 at 4:39PM
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The most famous statement attributed to the great P.T. Barnum is repeatedly proved anew!

You can't dry out or "freshen up" the damp air in your basement by bringing in new damp air from the outside or recirculating air from upper stories. And any air you expel with fans is replaced by damp air drawn in by air pressure and capillary action through all the cracks and crevices in the foundation walls and indeed the wall itself. Concrete blocks and poured concrete are hygroscopic--they absorb water and allow water to move through them. Return air systems with air conditioning can help. As can living in a desert. As can completely damp proofing and existing old basement.

But the simplest, cheapest proven ameliorative for a damp basement is a mechanical dehumidifier.

For true building science from experts with nothing to sell you, see the linked pieces by Dr. Lstiburek and others.

    Bookmark   December 18, 2011 at 1:02PM
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We live near the coast and put a Humidex system in our subterranean garage area. Within days the crawl space was dry, the air was not musty and most surprisingly, our son's asthma cleared up. That was 5 1/2 yrs ago and he has not had an asthma attack since. I don't know how it works, but it has been a tremendous help to us.

    Bookmark   January 1, 2012 at 6:19PM
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"We live near the coast and put a Humidex system in our subterranean garage area. Within days the crawl space was dry, the air was not musty and most surprisingly, our son's asthma cleared up. That was 5 1/2 yrs ago and he has not had an asthma attack since. I don't know how it works, but it has been a tremendous help to us."

Opening a window and running a fan likely would have done the same thing.

How much to box fans cost nowadays?

    Bookmark   January 1, 2012 at 8:11PM
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We spent 1,200 dollars on the humidex and this isa total loss for us. I did nothing. It couldn't even dehumidify our mudroom much less the first floor that I was promised it would be able to keep dry. It's kind of like a Suzy bake oven. Buyer beware.

    Bookmark   July 16, 2013 at 11:47AM
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I would stay away from the Humidex product. Overpriced and does not work. Switched to a dehumidifier. Support/Warranty is useless.

    Bookmark   July 27, 2014 at 4:17PM
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The best and cheapest appliance to remove basement humidity and mold is the Breeze. It works on the same principle as other systems (Wave Ventilation, EZ Breathe, and Humidex), just costs more than a thousand dollars less: only $299. And, it carries a 5 year warranty. Why would anyone pay over $1,500 for the same thing or recreate the wheel by trying to make one yourself when you can buy a professionally made one at that price? I have it in my basement and it works like a dream using the same principle employed in the expensive units. It costs about $12 a year to run continuously. Check it out: or at Amazon or Ebay.

    Bookmark   September 3, 2014 at 8:40AM
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