Curious on what everyone thinks about these fans that claim to remove cooler damp air from finished basements.
primitivelamps
| Posted in Energy Efficiency and Durability on
The two that I come across are Airtech and Humidex. The “science” behind them doesn’t seem to add up for me. Just wondering what others views are on these products.
Terry
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From the Airtech site: "At the same time, cleaner, fresher air is drawn down from the upper levels. This process creates an exchange of air for your entire home." Certainly an easy way to waste energy by making your heating and AC system work harder. But not in any way a substitute for a properly insulated and air/moisture sealed building enclosure and properly designed mechanical system.
Terry, call and chat with the companies. I could see the idea being useful for some homes and situations. I know for my home when I run my dehumudifier the electric bill takes a noticeable hit.
Also maybe the companies could point you to an installed unit to check out or ask about.
Hi AJ
I see these units installed by mold remediation company's in finished basements. A couple concerns I have are as follows : 1 They are depressurizing the basement. This could draw radon into the basement. Also if there are atmospheric vented appliances this could cause backdrafting. 2. If I understand these right they are assuming air is being drawn from conditioned spaces upstairs. This may or may not be true. 3. I have found evidence of mold in many finished basements with these installed.
Looks like a great fan for me since my home will be unheated in the winter and thus could not have a typical dehumidifier running..
I believe that the concept makes sense and we have been doing something similar for some time with a little Panasonic 70 CFM bath fan when we have sealed crawlspaces with tight (steel backed w/ good weather stripping) crawlspace doors. We measure the air flow post completion with a flow hood (with the crawl space door closed) as part of our confirmation of hitting our ASHRAE 62.2 fresh air goal. We find we do get pretty close to 70 CFM here whereas we get much less than rated flow out off the 110 cfm motion sensor/timer bath fans due to the ducting. Our assumption is that it is not possible to remove 70 cfm from a house without having the make up air come in from distributed locations (door thresholds, inactive dryer, range and bathroom exhaust dampers). We typically also provide a 6" cape sock damper behind the laundry dryer as a passive air intake but hood tests show that it only accounts for 50% of the make-up air from our exhaust fans.
Typically we will run the exhaust through hard steel duct up the back of the chimney chase to above the roof on the theory that if the fan (which is on a GFCI outlet) were to fail we would have stack effect as a back-up. By depressurizing the crawlspace 24/7 we can keep the radon, mold, and termite poisons from entering the home, so this is a component of our radon mitigation strategy as well.
What I don't like about the systems in the links is that they don't list the cfm ratings on the units and they are dehumidistat controlled rather than 24/7 at a rated air flow. I have used stand-alone dehumidistats to turn on a light to warn the home-owner of a humidity problem in the crawl and also to send power to a conventional dehumidifier. I prefer to have the client call me to report that there is a moisture problem in the sealed crawl rather than have a dehumidifier turn on automatically and burn up a lot of power trying to dry out a crawl without taking action on the source of the humidity. A dehumidistat feeding power to a light bulb doesn't need to be GFCI protected in the way an outlet feeding a dehumidifier does so it is more reliable in an area where lightening storms routinely trigger power surges that trip GFCIs
Hi Michael
Thanks for the reply. I don't have a problem with what you are describing. I am more concerned when installed in existing finished basements that have already showed a history of moisture issues. I see these installed as a solution when in my opinion they are not addressing the moisture problem. You didn't mention anything about atmospheric appliances and radon. Thoughts?
Yes I agree that this is not an appropriate solution to a moisture problem.
Like treating a broken leg with pain killers but not setting the bones and putting on a cast. Need to find out where the moisture is coming from and address that.
I would not have atmospherically vented combustion appliances in a high performance house other than a kitchen range or an "air tight" wood stove.