I live in an older home and am running into an issue I’ve never had before. Basically any time the heater is not in use, humidity levels in the house soar. Humidity in the house regularly reaches 65-75% in the summer even with the AC set to 72 on a 100 degree day, so I don’t imagine the AC is turning off very much.
Any idea what could be causing this? The home was built ~1950 and is on a crawl space. It was completely remodeled about 4 years ago, including new heat & air. I rent and moved in about three years ago.
My landlord has been great - when I told her about it last spring, she immediately sent a handyman and an AC repairman. The handyman said there was almost no insulation in the attic and that was causing the issue. The repairman dismissed that idea and instead said the AC unit was too big for the house and needed to be replaced. I, not wanting my rent to be raised (I’m month-to-month and she’s never raised it), told her that if there was a cheaper option I would be happy to try that instead. So she purchased a dehumidifier and it does a decent job keeping the humidity below 50%. But I hesitate to run it at night or when I’m not home, so it’s pretty uncomfortable for about an hour after I return.
While it’s currently not an issue, based on past years I’ll start having issues again around March, so I’m hoping to get some ideas for potential solutions to pitch to my landlord before then. Would spraying more insulation in the attic actually help? Is something about the crawl space causing this? Or is replacing the AC truly the only solution?
Lack of insulation AND ventilation in both the attic and the crawlspace would be the on the top of my list of suspects. An oversized AC unit can cool the house quickly but without running long enough to effectively remove humidity from the air. This can lead to a cool but damp environment. You could try running the fan mode on the unit longer, or adjust the fan speed to give the unit more time to flow air over the coils. But I still think attic/crawlspace insulation and venting issues is probably the bigger issue.
I can’t help with permanent solutions to the problem, but I’m used to living with very high humidity and know it is PITA if you do much cooking. (Sugar gets lumpy, Bacon Salt becomes a brick, salt clumps, etc.)
It sounds like the immediate problem is under control so you probably aren’t experiencing those issues, and/or you don’t cook much. But if you are experiencing any kitchen frustrations, let me know and I can suggest work-arounds.
Is it possible to locate your dehumidifier somewhere so it can discharge into a drain, as opposed to filling up a reservoir that you have to dump out? Unless there’s some other reason you don’t like running it at night or when away from home.
On the dehumidifier front, I finally stopped using those rollabout dehumidifiers you get at big box stores and I invested in a proper high quality dehumidifier with built-in pump and drain.
I leave it running in my basement all year long, with an appropriate setpoint, and it keeps kicking on and off as it dutifully sucks a few gallons of water out of the air every day.
Now my basement is no longer damp and musty even in the muggiest part of summer.
You also mention an attic and a crawlspace. The house might have been originally intended to use an attic fan in the warm weather to perform most of the cooling and keeping the place dry. The crawlspace needs air circulation or humidity can build up in there. It should be well vented with screening and lattice over openings. An attic fan will draw air through there and up through the house which will keep it generally cooler and dryer. However, since you have an A/C the proper venting in the crawlspace and between floors may no longer exist. Separate fans may be needed in the attic and crawlspace to keep them ventilated.
Altogether, it sounds like there is an oversize A/C to account for loss from lack of insulation and unvented space at the bottom and top of the house, and the secondary result is high humidity as @Dorjan describes. I think the owner of the house would want to take care of this to preserve the house. If an attic fan by itself with occasional use of A/C doesn’t work out then I would recommend separate attic and crawlspace fans, along with proper insulation and sealing of the living space so the A/C can work properly.
The OP doesn’t tell us where they live, or how humid the outside world is.
If the interior humidity came on suddenly, I’d be looking for a plumbing leak in or under the house, or a downspout or groundwater problem leading to the house sitting over perpetually damp or wet ground.
If the house has been this way since the OP moved in, it’s probably a permanent feature of the issues already raised b the other posters. Or at least has been permanent since that HVAC unit was installed.
Thanks Carol - so far I’ve mostly found work arounds but I might PM you in the future!
Unfortunately not - I do not have any floor drains and the model my landlord purchased does not have a pump so it could drain into a sink.
And I don’t like to leave it running when I’m not here due to a bad experienced with dehumidifiers the first year I moved in. That first summer I purchased one just to see if it would help and I had three break in as many months (one quite loudly at night) and then gave up on them.
I do not know but will try to check when I can. Should it be easily visible or could it be covered up?
I live in Oklahoma. So it can be humid, but it is frequently much more humid in the house than it is outside.
The handyman did check for a leak under the house and did not find one. I’ll look around the house after the next rain to see if there’s any drainage issues.
And thanks everyone for your suggestions! I think I’m leaning towards asking her to add more insulation and put in a vapor barrier if there is not one.
I don’t actually know. The one fairly recently installed in my basement is extremely visible – it’s a bright white sheet – but I don’t know whether they all are; or whether yours might be covered over with something.
If you can see bare ground underneath and bare beams above, however, I’d guess that there probably isn’t one – unless it’s between the floor surface and its underlayment layer.
Somebody who knows more about this than I do might step in here.
I would certainly inspect the crawl space for a plastic vapor barrier covering at least 90-95% of the ground. I had a high humidity issue in my home causing some minor mold in closet areas and installing a vapor barrier resolved this. When looking at the crawl space, try to determine if any black or white mold is visible on the floor joists as this is a definite sign of high humidity.
No doubt you’re aware that dehumidifiers address the symptoms of the issue but not the cause. Others mentioned an oversized a/c will not remove humidity which would explain summer humidity but if humidity is also high in the winter, the cause may lie elsewhere and many times its source can be from the ground up.
Don’t worry about it, I read the quoted part in your post and saw the exact thing you saw, with the same puzzlement.
“three break ins in as many months (one quite loudly at night)” instead of “three break in as many months (one quite loudly at night)”
The parenthetical part fits the incorrect reading quite nicely.
And I have already been sipping my coffee for some time this morning.
So sorry about the break in confusion, but thanks for the good laugh today
Thank you for this information. I’ll try to look in the crawlspace this weekend when it’s light outside. Do you know if the vapor barrier should be visible or could it be covered by something?
And humidity in the house is only low when the heater has been running. As soon as there are nice days where neither heat or AC is needed, there’s a noticeable increase in humidity pretty quickly.
I have seen only one vapor barrier covered. A neighbor had water seeping into his crawlspace and decided to install 6 - 8" of sand on top. This did nothing to either reduce humidity or solve the water issue and only offered a coverup of the symptoms. Not a wise choice in my opinion.
I had water seeping into my crawlspace after heavy rain and decided to fully encapsulate the crawlspace. It was expensive for my 1400 sq ft home at about $9,000 but this was far cheaper than the potential of dealing with mold and rot. I have a dehumidifier down there and monitor and control it through an app. I have never regretted that decision. Encapsulation may not be necessary for you but if you lack a vapor barrier, that would be my first approach.
What kind of heating system is used, and what is the condition of the chimney? Older, less efficient boilers and furnaces would keep the chimney warm enough to dry out any rain driven in from the top or through poorly pointed exposed masonry sides. Newer systems don’t waste as much heat, and a chimney can become a giant brick sponge running all the way down through your home…
