Humidity 101
August 23, 2024 9:59 AM Subscribe
What is the best way to make sure the humidity is acceptable/healthy/not going to grow mold at my place? And how to maintain everything related to that. Because I don't know and cannot tell.
Here are the relevant details (sorry for this boring long list - trying to answer potential questions):
782 sf townhouse, one- story, between two other units (4 units total for the building).
High ceiling in the main room. There is a ceiling fan but it's right at the front door and not in the main space with the higher ceiling - it is running constantly at a low speed.
I moved in last fall, got a hygrometer and then a warm mist humidifier for the bedroom, to try to keep the place at 45-55 humidity instead of sub 30 (late Fall and Winter), and it seemed to do the trick. The bedroom is always the most comfortable in the house (which is great, I spend most of my time there) but the rest of the place is a bit colder in the winter and warmer in the summer - I'd say by several degrees as a guess.
As temps increased mid-late Spring, the hygrometer began reading 70 or higher, which seems crazy? I determined I don't have a dehumidifier with the furnace and got some of those Damp-Rid bags. One in the bathroom and one in the laundry room (which also has the floor access to the lower crawl space and furnace.) The bathroom does have a fan, and the mirror fogs very little or not at all when it is on for a shower. I don't close the bathroom door. The bathroom vents into a small upper crawlspace and out through the roof. The home inspection noted very minor dark spots up there - he did not think it seemed like a problem but did suggest a mold inspection because he is required to (and which I have not done).
The Damp-rid bag hanging on the back of the bathroom door has filled up and been replaced twice so far (approx 3 months), so I'm on the third one and I prefer not to use those and fill up landfills but I'm just trying to get a handle on things.
Over the summer I had to replace the air conditioner (it was 23 yrs old). The installer said the AC would suck all the water out of the air, and it seemed to help early on, but then the hygrometer was (and continues to be, many days) up to 70 again. I have kept the thermostat at approx 70-72, and also have a small fan in the bedroom running because the dogs like it.
Someone at the office had a dehumidifier they did not need, so I took it home and got that running. I set it to turn itself off at 45 humidity. It also shows 70 at times, but usually closer to 50 and it does go off once in a while - but the chamber has never had water in it. It's in the laundry room where the second Damp-rid bag is hanging (and also a Damp Rid tub), so maybe the water is sucked into the room and goes in those first?
Some days the hygrometer (in the bedroom) says 70 and then a couple hours later it's down to 45 and I have no idea why. Outside weather/temp I guess?
I should probably open the windows and sliding glass door and air out the place? but so far I just keep all the windows and doors closed. If I really need to open windows and stuff, I will. If so, how often? (The two windows in the bedroom I have covered with heavy drapes and furniture and never intended to open them - partly because they open directly onto the walking path in front of the unit.)
Finally, the insulation in the lower crawlspace is basically crap. The pink kind is mostly fallen off the walls, and there is no moisture barrier on the floor (the home maintenance guy suggested I get something like that - basically a plastic sheet to go over the gravel) but I've also been told it won't make much difference.
It's my first place, me and my dogs, and I am a complete noob at all the things so if you are hesitating to say something obvious, don't.
Here are the relevant details (sorry for this boring long list - trying to answer potential questions):
782 sf townhouse, one- story, between two other units (4 units total for the building).
High ceiling in the main room. There is a ceiling fan but it's right at the front door and not in the main space with the higher ceiling - it is running constantly at a low speed.
I moved in last fall, got a hygrometer and then a warm mist humidifier for the bedroom, to try to keep the place at 45-55 humidity instead of sub 30 (late Fall and Winter), and it seemed to do the trick. The bedroom is always the most comfortable in the house (which is great, I spend most of my time there) but the rest of the place is a bit colder in the winter and warmer in the summer - I'd say by several degrees as a guess.
As temps increased mid-late Spring, the hygrometer began reading 70 or higher, which seems crazy? I determined I don't have a dehumidifier with the furnace and got some of those Damp-Rid bags. One in the bathroom and one in the laundry room (which also has the floor access to the lower crawl space and furnace.) The bathroom does have a fan, and the mirror fogs very little or not at all when it is on for a shower. I don't close the bathroom door. The bathroom vents into a small upper crawlspace and out through the roof. The home inspection noted very minor dark spots up there - he did not think it seemed like a problem but did suggest a mold inspection because he is required to (and which I have not done).
The Damp-rid bag hanging on the back of the bathroom door has filled up and been replaced twice so far (approx 3 months), so I'm on the third one and I prefer not to use those and fill up landfills but I'm just trying to get a handle on things.
Over the summer I had to replace the air conditioner (it was 23 yrs old). The installer said the AC would suck all the water out of the air, and it seemed to help early on, but then the hygrometer was (and continues to be, many days) up to 70 again. I have kept the thermostat at approx 70-72, and also have a small fan in the bedroom running because the dogs like it.
Someone at the office had a dehumidifier they did not need, so I took it home and got that running. I set it to turn itself off at 45 humidity. It also shows 70 at times, but usually closer to 50 and it does go off once in a while - but the chamber has never had water in it. It's in the laundry room where the second Damp-rid bag is hanging (and also a Damp Rid tub), so maybe the water is sucked into the room and goes in those first?
Some days the hygrometer (in the bedroom) says 70 and then a couple hours later it's down to 45 and I have no idea why. Outside weather/temp I guess?
I should probably open the windows and sliding glass door and air out the place? but so far I just keep all the windows and doors closed. If I really need to open windows and stuff, I will. If so, how often? (The two windows in the bedroom I have covered with heavy drapes and furniture and never intended to open them - partly because they open directly onto the walking path in front of the unit.)
Finally, the insulation in the lower crawlspace is basically crap. The pink kind is mostly fallen off the walls, and there is no moisture barrier on the floor (the home maintenance guy suggested I get something like that - basically a plastic sheet to go over the gravel) but I've also been told it won't make much difference.
It's my first place, me and my dogs, and I am a complete noob at all the things so if you are hesitating to say something obvious, don't.
Energy Vanguard blogger and building science dude Dr. Allison Bailes has lots of posts on indoor humidity, including the argument for paying attention to dew point temperature instead of relative humidity and the need (or lack thereof) for bathroom fans. I don't have specific advice for you, though, but this is an excellent resource for info.
posted by spamandkimchi at 1:47 PM on August 23 [1 favorite]
posted by spamandkimchi at 1:47 PM on August 23 [1 favorite]
Make sure you're changing HVAC filters, cleaning the bathroom exhaust fan, and performing maintenance on the dehumidifier on schedule. (Put in the model number at the manufacturer's site, for a .pdf of the instruction manual for your former-office machine.)
posted by Iris Gambol at 4:15 PM on August 23 [1 favorite]
posted by Iris Gambol at 4:15 PM on August 23 [1 favorite]
^I'm a real fumble-fingers today. You're a person with dogs, plural; your filter-changing/fan-cleaning etc. schedule might need to be more frequent than one followed in an unfortunately dog-less household.
posted by Iris Gambol at 4:20 PM on August 23 [1 favorite]
posted by Iris Gambol at 4:20 PM on August 23 [1 favorite]
When you say that the dehumidifier "goes off once in a while," do you mean that it runs continuously and only stops running occasionally, or that it is mostly idle and only turns on once in a while? Either way, if there's no water in the chamber, it's not pulling any water out of the air.
If it runs continuously but doesn't collect any water, then it's not working properly. IME the most likely situation is that the coolant has all leaked out and it's a goner; send it to hazardous waste disposal and get a new one.
If it is mostly idle and hardly runs at all, and doesn't collect any water, but you've got it set to 45% humidity, then you're just fine (for summer): your ambient humidity is generally lower than 45%, so it doesn't need to do anything. If, however, you're pretty confident that the ambient humidity is more than that, then the sensor on the humidifier is probably busted and it's a goner; send it to hazardous waste disposal and get a new one.
I'm sorry that "throw out your humidifier and try again" is a recurring theme here, but (again IME with a damp basement in the US midwest) most big-box-store humidifiers aren't built to last and aren't feasibly repairable.
posted by spamloaf at 6:13 PM on August 23 [4 favorites]
If it runs continuously but doesn't collect any water, then it's not working properly. IME the most likely situation is that the coolant has all leaked out and it's a goner; send it to hazardous waste disposal and get a new one.
If it is mostly idle and hardly runs at all, and doesn't collect any water, but you've got it set to 45% humidity, then you're just fine (for summer): your ambient humidity is generally lower than 45%, so it doesn't need to do anything. If, however, you're pretty confident that the ambient humidity is more than that, then the sensor on the humidifier is probably busted and it's a goner; send it to hazardous waste disposal and get a new one.
I'm sorry that "throw out your humidifier and try again" is a recurring theme here, but (again IME with a damp basement in the US midwest) most big-box-store humidifiers aren't built to last and aren't feasibly repairable.
posted by spamloaf at 6:13 PM on August 23 [4 favorites]
I’m very sorry: please replace all instances of the word “humidifier” in my comment above with “dehumidifier.” D’oh.
posted by spamloaf at 4:43 AM on August 24 [1 favorite]
posted by spamloaf at 4:43 AM on August 24 [1 favorite]
Just a tip to avoid mold, don't place your furniture so it's right up next to the wall, make sure that air can circulate behind your furniture.
posted by Sar at 4:07 PM on August 24 [1 favorite]
posted by Sar at 4:07 PM on August 24 [1 favorite]
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Bear in mind that humidity is relative and warmer air can hold more moisture. So if you take 50% RH air at 25C and cool it down to 20C, you now have 65% RH air.
All that said, ventilation is important for moisture management, and also for indoor air quality. If you don't have any kind of ventilation installed, you may want to consider a blower door test to determine how much air leakage you have and if you might benefit from a heat recovery ventilator.
posted by ssg at 11:36 AM on August 23 [4 favorites]