Wave ventilation system
Beware These 3 Expensive Ventilation System Ripoffs
How much does an exhaust fan cost? Search online and you can find lots of them that move 200 cubic feet per minute (cfm) for $100 to $150. But, if you put one in a semi-attractive (emphasis on the "semi") package, create some fancy marketing materials, and target people who don't know much building science, you can charge $1200 to $1700 for that same fan. At least that seems to be the business plan for these three companies.
I found out about them only recently, but a quick search online shows that people have been discussing whether or not they work at least as far back as 2008. The systems I'm talking about are made by WAVE, EZ Breathe, and Humidex, and, for most people in the US, they won't work as promised.
What they say
Reading through the crap on their websites would be funny if everyone knew enough building science to see through it. Here are a few of the things they say:
Using less energy than a 40-watt light bulb, WAVE Ventilation units expel harmful gases, toxins and pollutants, replenishing your home with fresh, clean, moisture-free air. [WAVE]
They don't tell you that the air you replenish your home with will probably contain even more moisture than the air you're exhausting.
Why use costly energy (in the form of electricity) to condense this water vapor into liquid form like traditional dehumidification products do? Simply remove this moisture from your home for pennies a day! [EZ Breathe]
They all seem to be targeting the dehumidifier market, but they say nothing about climate or the dew point of the outdoor air they're bringing in. They also conveniently ignore the cost of conditioning the outdoor air their systems bring in.
Generally moist, stale, polluted air tends to become trapped in the lowest part of your home. If it isn’t dealt with, it can quickly move to the upper levels of your home. [Humidex]
Ah, yeah. It gets trapped, but watch out! That trapped air can escape quickly.
In the summer, when there is no air conditioning in the upper levels, the warmer air flows downstairs raising the temperature, which lowers the relative humidity and raises the dew point resulting in less condensation. [WAVE]
Raising the dew point of indoor air does NOT result in less condensation. In fact, condensation is more likely.
What they're supposed to do
These systems are nothing more than glorified exhaust-only ventilation systems. The main target for these companies is someone with a humid, musty smelling basement or a damp crawl space. They promise that by exhausting air from the basement or crawl space, dry, conditioned air from the living space above will be brought down into the basement or crawl space. The result is a dry basement or crawl space. Or so they'd have you believe.
If you've been following this blog for a while, you probably know the pitfalls of an exhaust-only strategy. One of the main problems is that you don't know where the makeup air is coming from. For every cubic foot of air that gets exhausted through one of these fans, another cubic foot of air has to come into the house somewhere.
Interestingly, only one of the companies (EZ Breathe) shows you where that air comes in. and that's because they want to sell you another piece to go with that expensive fan. It's good that they acknowledge the need for outdoor air to be brought in from a known place. Their balanced system even tempers the outdoor air by mixing it with indoor air before delivering it to the house. To claim, however, that "the E·Z Breathe Advanced Balanced Ventilation System delivers all the benefits of ERV and HRV systems at about a third of the cost" is probably not true.
The other two companies show you diagrams with arrows, like the one above from WAVE, but notice they don't show you the arrows of outdoor air coming into the house. If you believe that diagram, it looks like they're ventilating the house with indoor air.
Their basic idea is that the air in the house will be more humid than the outdoor air enough of the time that exhausting indoor air and bringing in outdoor air results in a net drying effect of the air. What do you say, New Orleans? Care to try that?
Why they won't work
That's the basic problem with these systems. Exhaust-only strategies are bad for humid climates because the outdoor air isn't drier than the indoor air most of the time. Along the Gulf Coast, there's almost never a time when you could benefit from one of these. Even farther north, they'll have limited effectiveness for much of the year anywhere east of the 100th meridian, the longitude that (roughly) separates the wet from the dry climates of North America.
I explained this problem last year when I wrote about why crawl space vents don't dry out crawl spaces in humid climates. The psychrometric chart below (click for large version) shows what happens on a summer day when you bring outdoor air inside and cool it down. If you're keeping the house at 75° F, it's even worse. The relative humidity of that air goes up to more than 80%.
During cold weather, when the outdoor air is dry, these systems will bring in cold, unconditioned air in any climate. That $2 to $4 per month they promise it will cost you to operate the system doesn't account for the extra cost of conditioning all the outdoor air you're bringing in. Yes, you'll dry out the indoor air in cold weather, but the more cold air you bring in, the more expensive these systems are. You may also experience comfort problems from drafts and heating systems that can't keep up, especially in a winter as cold as the one we just had.
What should you do for a humid basement or crawl space?
As with any problem, the first thing to do is go after the causes, not the symptoms. For crawl spaces, especially in humid climates, encapsulation is the best answer. Even in dry climates, it's a good idea to keep soil gases like radon out of your home.
If you've got a
humid basement, look for sources of moisture that you can eliminate before doing anything with the air. First on the list is to look for exterior water problems. In many cases, bad gutters or incorrect slope in the yard are the culprits. If your home has a crawl space connected to the basement, it's probably adding a lot of water vapor. Also look for air leakage sites between your basement and the outdoors. Get a blower door test to find out how bad it really is and target your air sealing efforts.
Once you've eliminated all the sources of moisture you can do cost effectively, then it's time to start considering what to do with the air. Maybe adding air conditioning to the basement is all you need to do. Most basements don't have much cooling load, though, so the AC may not run long enough to dehumidify completely.
At that point, a dehumidifier will be a better solution than one of the ventilation systems made by Humidex, WAVE, or EZ Breathe. If you want to do it without adding a lot of heat and without adding a lot to your electricity bill, get one of the high efficiency, high capacity models, like the ones made by Thermastor. (Disclosure: Thermastor is an advertiser here, but I would make the same recommendation even if they weren't. I've been recommending their products for a long time and installed them when I was a contractor.)
The three companies I named above, Humidex, WAVE, or EZ Breathe, are relying on people who don't understand how air and moisture work. Here's a quick rundown of the problems:
- The products are expensive ($1200 to $1700).
- The operating costs will be higher than advertised because the cost of conditioning the outdoor air the systems bring in isn't included.
- They don't work in all climates or during all times of year.
- They could cause backdrafting of combustion appliances because of the negative pressure they induce on the home, possibly resulting in carbon monoxide in your home.
- They could bring more radon into your home.
- If you run them at their highest rates (>200 cubic feet per minute), you'll almost certainly exceed ASHRAE 62.2 ventilation rates (unless you have a 5000 square foot, 7 bedroom house or larger).
If you make the mistake of getting one of these systems, you'll almost certainly be throwing your money away. And that might be your best outcome.
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NOTE: Comments are moderated. Your comment will not appear below until approved.
As usual, your well-thought out critique, questioning. check that. very specifically pointing out, the shortcomings of these "systems" provides a valuable service to less well-informed contractors and homeowners who are considering them, and as the hit count on this article increases, I'm sure it will climb in search engine rankings.
While I always admire your candor and forthrightness in publishing information of this type, I don't need to remind you of the looming cloud of legal action from aggrieved manufacturers.
No matter how right you are, you may still find yourself in the unpleasant position of haveing to defend yourself in a court of law. I fervently hope it does not come to that, and while I know such concerns have never stopped you before, I wish you well and, again, congratulate you for clearly and intelligently blowing the whistle on these "systems".
Posted @ Tuesday, June 10, 2014 10:24 AM by Steve Waclo
Truth remains an absolute defense against libel.
This seems yet another example of an over-priced over-hyped misleadingly-marketed greenwashed product.
It's like playing Whack-a-Mole - one can never have a big enough hammer, nor swing it fast enough against these things.
Posted @ Tuesday, June 10, 2014 12:22 PM by Nate Adams
More snake oil. Thanks for the exposé. The only way to stop this nonsense is through education, and you're the only guy out there doing something about it.
In the section on what to do about a humid crawl or basement, it's worth mentioning source control -- things like clean gutters with leaders away from foundation and diverting runoff. Without that, nothing else really matters.
Posted @ Tuesday, June 10, 2014 1:08 PM by David Butler
Steve W.. I certainly appreciate your concern, and I didn't hit the publish button without careful consideration of what I might be getting myself into. I was able to survive the threats of a much larger company than these so I think I'll be OK. Plus, people need to know how to evaluate this kind of stuff.
Curt K.. But it's still fun to play the game!
Nate A.. You're welcome.
David B.. I'm not the only one. Martin Holladay does a great job of it in his Musings of an Energy Nerd column at Green Building Advisor. Excellent point about source control. That one escaped me as I wrote, but I'll put it in there now.
Posted @ Tuesday, June 10, 2014 1:19 PM by Allison Bailes
I'm no doubt among the minority of your readers not intimately conversant in minutiae of the Lanham Act (as mentioned by General Counsel in letters you linked to from your last kerfuffle) so, for the benefit of the two other folks, here are some details:
"15 U.S.C. § 1125(a)(1)(A) is often used when false or misleading statements are alleged to have hurt a consumer or business. The claimant must prove that a false or misleading statement was made in commerce and that the statement creates a likelihood of harm to the plaintiff."
And if things break bad, I can refer you to attorney I know well (don't ask) over at the Three Stooge's counsel of choice, "Dewey, Cheatem and Howe".
Posted @ Tuesday, June 10, 2014 3:54 PM by Steve Waclo