Whole-House Dehumidification
As the title states, I have question about dehumidification. My brother recently moved into the house that my grandfather self-built in 1992. It is a 1,700 sqft basic ranch on a crawlspace in SW Ohio. I would say that the house was tighter than normal in its time (2×6 walls, with 1/2″ foam sheathing) but I doubt it is tight by today’s standards. Maybe it is tighter than I think though, because they are battling high humidity in the house. I spent a lot of time in this house growing up and I don’t remember this being an issue. I am guessing it is mostly due to lifestyle, folks that grew up during the depression lived differently, to say the least. Their temporary solution has them running a standard dehumidifier in the family room for a good portion of the day, but it is noisy and takes up valuable floor space. Are there any whole house solutions that are able to be reasonably retrofitted.
I am assuming the humidity problem is coming from people, showers, cooking, etc and not external sources since it wasn’t issue in the past. Do you think My assumptions are correct? Any and all advice is appreciated.
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Replies
Jacob,
There are many options for whole home dehumidifiers, but first I suggest you determine the cause(s) of the moisture problem. What are the symptoms you are seeing which make you suspect a moisture problem in the house? You mention showers and cooking - does the house have extraction fans in the bath and kitchen which direct the exhausted air outside the house and are these fans used when the cooktop or shower is used? The house incorporates a crawlspace - have you checked the condition of the crawlspace? Is it moist or wet? Typically the crawlspace communicates well with the first floor of the house above it. Does the house have a ducted HVAC system? Are the return and supply ducts properly connected and in good condition? Closed/open doors can change the way a house is ventilated when the ducted HVAC system operates - does your brother keep rooms closed/open in a different way than your grandad did? Answering these questions will help you determine what has changed and identify possible causes to be addressed.
Similar issue with a similar era and build of house. We are up north (British Columbia) in a pretty wet/humid interior valley. Have two single head heat pumps - one for a basement suite and one for our upstairs. Basement humidity is fine, usually around 40% humidity. We struggle to get the upstairs under 50% humidity during the winter. It's just my wife, my 5 year old and I living upstairs. We run bathroom fans when we shower, the range hood when we cook. I don't have answers yet, but am following to get some ideas. One thought - I wonder how much built-in dishwashers contribute to the problem?
I have not found typical residential dishwashers cause moisture problems unless they are leaking water. They do not run often and are enclosed so nearly all of the water goes down the drain and gets pumped out.
Do you experience moisture problems on moderate days with little or no heating or cooling system operation? If this is the case a dehumidifier may be a proper solution. In some climates the dew point of outdoor air is high enough to cause moisture problems inside the house even though the temperature outdoors does not cause the house to need much heating or cooling.
Internal gains (people and appliances) are not high enough to cause moistures problems.A typical person will produce around 0.25 pound of water per hour. That's not a lot. Your moisture problem is probably the result of too much air infiltration if it's humid outside as well. You need to seal your house. There are probably couple of big holes somewhere in your ceiling. Any pot lights in your ceiling?
I don't live there and they (my brother and his wife) aren't really the building science type. I would go as far as to say they do not even know they have a problem, but when I visited, I told them there humidity level was way too high. Condensation on the windows into overall felt humid in the house. Crawl space is generally dry by crawl space standards. Poly on the floor though crawl space and polystyrene insulation glued to 4 ft foundation walls. It's probably time I talked them into ceiling up the crawl space and making it conditioned space. If they did that that would make for plenty of room to install a whole house to humidifier. They already have one that runs in the crawl space. I will have to do some investigating on the HVAC system to make sure there are no major leaks or problems in that area. They don't have this problem of the summer time, I'm assuming the air conditioning system takes care of the humidity then.
Condensation on the windows in winter may be caused by inadequate ventilation (for the occupancy) and/or poor thermal performance of the windows. Cold climate houses typically get too dry in the winter as the outdoor air has a very low moisture content. If the moisture problems appear in the spring/fall when there is not much heating or cooling system operation, a dehumidifier can help.
Sealing up the crawlspace and placing a sealed impermeable barrier over the soil in the crawlspace will improve the comfort of the house. Here is a company (I work for them) that produces high efficiency residential dehumidifiers if you want to see some options.
https://www.santa-fe-products.com/
You can get your brother a thermohygrometer which displays temperature and humidity in the room where it is located to visually demonstrate the moisture level in the house. If you want to log the conditions in the house over time you can get a datalogger which will record the temperature and humidity at specific intervals. I use dataloggers from this company (but I am not affiliated with them - just a customer)
https://www.onsetcomp.com/products/data-loggers-sensors/relative-humidity/
I'm not necessarily saying it is good reasoning, but my thought that it was coming from their "living" was because I live in the same area but in a newer but much more leaky house. And I have to run a whole house humidifier to keep my rh above 30%. I guess it could be coming from the crawl space as well. There's always something to figure out...
I see a lot of suggestions for checking for moisture issues. And that's a good place to start. But I'd also be interested in common/suggested options for whole home de-humidification (assuming moisture is taken care of). Anyone have any tips to answer the OP?
https://www.santa-fe-products.com/
Provides ducted and unducted residential dehumidifiers. Disclaimer - I work for this company. Feel free to poke around our website or call us if you have questions.
Thermastor (Santa Fe) makes high-efficiency dehumidifiers meant to be installed with ductwork, either with or without integration with the central HVAC system. AprilAire also makes some dedicated whole-house systems.
The reason most of the focus here has been on moisture sources is that it is best to locate and deal with moisture at its source rather that letting it come inside and then trying to remove it. Dehumidifiers make noise and use energy. Sometimes they are necessary once you've dealt with all the direct sources. But using them is sort of like catching your blood in a bucket after an injury rather than buckling down and getting stitches. The stitches hurt, but in the long run they are a far better option.
Peter is correct - often dealing with water (liquid or vapor) ingress by improving the building is a 'buy once cry once' situation. A dehumidifier can help deal with this problem water but you have to pay for every pint it removes over and over. A dehumidifier may still be required to deal with moisture from occupants/activities/ventilation, but you may be able to use a smaller capacity dehumidifier (which creates less heat) and have more options as to how you apply the dehumidifier to your house if you fix the major problems first.