Hello, I am considering a whole-house dehumidifier and was wondering if there are any health concerns regarding pressurizing a home.
heat-tech
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I am on the tail end of a large renovation project. The house has spray foam top bottom and sides. If I don’t need an hrv/erv all the better, I am mainly interested in adequate fresh air and lowering the RH. I am in Massachusetts. Thanks for any help/comments
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Gary,
Most homes in Massachusetts don't need a whole-house dehumidifier. But if you house is insulated with spray foam, you certainly need a mechanical ventilation system -- probably an HRV.
For more information, see Designing a Good Ventilation System.
Gary,
Some whole house dehumidifiers (such as the Ultra-Aire dehumidifiers manufactured by my company) will provide positive pressurization ventilation of your house negating the need for an HRV or an ERV. The whole house dehumidifier will actively dehumidify your house unlike an HRV or ERV. We have not seen any negative health effects caused by positive pressurization ventilation. For all mechanical ventilation systems, you should make sure that your outdoor fresh air source is in a suitable location that is not affected by contamination sources outside the conditioned enclosure of your house.
http://www.ultra-aire.com/
ahhh the good old contrasting opinion, Tim, are there any studies I can read up on regarding the erv/hrv vs fresh air/dehumidify? I have ran across some good feedback on your system, but I would be grateful to understand more.
Martin, thanks for your write up, i printed it and will read it tonight when i get home.
I forgot to mention I am in HVAC, I own a blower door/duct blaster, have digital manometers, so an and so forth, I know the basics but i normally work in old houses retrofitting clunky hvac and boilers. I don't do new construction anymore, not enough $ in it for me. So, my home remodel has me asking questions about fresh air. Thanks for all the help.
Gary,
Tim is promoting a system than his company sells. His solution will be more expensive, both in terms of installation costs and operating costs, than almost all of the ventilation options mentioned in my article.
Martin, I have a 3 ton geothermal heat pump, I only need about 2 tons of ac on a hot day based on my manual J, so dehumidification has some appeal to me. It's 3 tons so i can get more heat out of it (that's why it's oversized)
Maybe i need both? At this point money is no object, i stopped worrying about that months ago when my project ballooned into a major event.
Gary, reading this thread, IMO call Tim and give his system a go. Let us know if you feel the love as you move forward...
Interesting thread as I have no issue with interior humidity but it knocks my socks off while laboring in it, though the creaky knees love it.
Gary,
In Massachusetts, a properly operating AC system should take care of your dehumidification needs almost all of the time. Do you have evidence of a problem?
Martin, I am not living there yet, we are almost done with construction. I am purposely over-sized on AC, I don't know what you know about hvac, I am going big to get more juice out of my heat pump in winter (less costs on my gas bill), which leaves me with a larger than needed ac. This is not abnormal prcatice when it comes to HP. There are many days in new england where the humidity it high but the ambient isn't, requiring latent energy removal. Plus, if the air is dryer the ac will run less keeping the ac at set point. Let me read your article so i don't repeat something we both already know.
Martin, very nice article, I am not familiar with some of the basic methods you wrote about though. If I push fresh air in with the dehumidifier method won't the potential excessive pressure just find its way out of the home via bathroom fans and kitchen exhaust? And/or, can't i simply push air into the house in short cycles to eliminate the possibility of 'excessive' positive pressure? Thanks, gary
Gary,
If you read my article on ventilation systems, then you know that you can choose a supply-only ventilation system (or, for that matter, an exhaust-only ventilation system) if you want. If properly designed, there is no reason to worry about how the air escapes from your home. Ventilation air flows are very low -- on the order of 40 to 80 cfm. A ventilation system will not significantly pressurize or depressurize your house.