A new customer is scratching their head as they watch their clothes growing mold in the closets. Their dehumidifier is running in he basement. To me is seems to be a problem in the walls where moisture is collecting due to lack of moisture barrier? Not sure what could be a reasonable plan of attack? Maybe I should check their heating system out. Thanks for the feedback.
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
Listeners write in about haunted pipes and building-science tomes, and they ask questions about roof venting and roof leaks.
Featured Video
Highlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
sounds like there is little insulation in the walls so water vapour is condensing where the dew point occurs in the hanging clothing. The solution might be to have less clothing in the closet - more air space. Or maybe more insulation.
Would a small heat duct in each closet help?
I'm sure it would help reduce
I'm sure it would help reduce condensation and, with less water available, there would be less mould. You would still have a problem, even though you would have dealt with the symptom.
Ron
Would a small heat duct in each closet help?
In a nutshell, yes.
But I think you'll find the most "cure" from the least amount of change, by cutting some off the bottom, and the top of each closet door.
Cutting off the bottom, allows air flow.
Cutting off both bottom and top, promotes it.
If you really feel the urge to do something more, get some "muffin fans" like they put in computers. Only 120v.
Install one of those in each door, at the top, (Or in the wall above the door.), and cut some off the bottom of the door.
That will force air flow.
I had this problem in humid SouthWest Georgia. My tenant's leather shoes were coated with mold. I researched it a little, wound up cutting about 3/4 inch off the bottom of the closet door, just to improve ventilation. This took care of it ! !
Greg
Hey Greg,I will check that out, I did not think of checkin how much room is between the doors and the floor so air can move around. Thanks
What is the climate?
Does this happen all year long?
What is the house construction? How old? What kind of insulation?
What is the indoor humidity levels?
What tempature is the bedrooms kept at?
The house is here in CT, have a lot of moisture. I believe the insulation is poor but the closets seems to be worse then the living spaces. I could tell them to put in a deal to check the humidity level. I have seen those little digital ones, that should help. Thanks
I've seen it in closets like
I've seen it in closets like that out here in the arid west. New house even ... and the lady was like a better homes and gardens housekeeper. The answer was 'simply' a tight house and little ventilation. The mold was because the closets are where little air circulation is and the higher RH collects there where there is an extra cold wall (also due to lack of air circulation). Why is the dehumidifier in the basement? Anyway, I suspect that high RH is the problem (still). What is the heating system type? Check for sources of humidity, too (e.g. house plants, aquarium, teenage daughters from heck taking LONG showers). Do they not run their bath fans much? How about cooking? (often a high source of moisture). Don't make knee jerk reactions until you study this beast a bit. It's easy to pull the first problem off the shelf and declare it THE problem. I've learned that moisture can be a bit of a head scratcher sometimes, so it pays to sit back, think, study, and cogitate (i.e. think in a really focused manner). Keep the laws of moisture well in hand at all times. Problem may be multiple as may be solutions.
Let me guess: This closet is on an outside wall, right?
With the closet door closed, no heat gets into the closet, and the temperature drops 10-20 degrees below that in the rest of the house, enough to promote condensation and mold.
A "quick fix" is to run an incandescent light 24/7 to keep the closet warmer. Slightly less quick is to somehow route some air from the furnace into the closet.
Unless the closet is in the basement, against a foundation wall, adding a vapor barrier won't improve things, since the "moisture drive", in CT, will be from inside to outside.
Are you in the construction biz?
I'm thinking most construction folks would realize how insufficient the information you have given is for any sort of diagnosis.
Start by answering all of Bill's questions; If you are trying to be a pro, immerse yourself in the building science web site. If the home has been around awhile, and the mold problem is new, my money is on they're having set a central humidifier way too high, and maybe running high indoor temps.
(Worst I've seen was some folks from a desert equatorial area running temps in the mid 70's and humdifier cranked to high.)
Maybe the humidifier is fighting the dehumidifier he mentioned. ;)
Maybe the humidifier is fighting the dehumidifier he mentioned is running.
Running high indoor temps? That will lower the RH, not raise it. He will have LESS of a tendency of having the condensation with higher temps. Maybe time to bathe yourself in a bit of additional building science? ;)
>>Running high indoor temps? That will lower the RH, not raise it. He will have LESS of a tendency of having the condensation with higher temps.
Ah, but the higher temps don't mean the exterior walls aren't cold enough to cause condensation.
And, actually, the warmer the air, the more moisture it will hold, and the more condensation you'll get on cold surfaces, like windows and, often, the inside of closets on an exterior wall.
Trust me, I have seen a house where they had the humidifier cranked to high and ran the temp in the upper 70's and in really cold weather, there was condensation on most of the exterior walls.
>>Maybe time to bathe yourself in a bit of additional building science? ;)
To know how the science works, it helps to (i) live in it (ii) study and think about what you experience, and (iii) try to make sure you think of all the factors involved.
{G}
But raising the indoor temp doesn't change the moisture in the air just because it is able to hold more moisture, it doesn't actually do it.
A higher indoor air temp will usually (almost always) translate to a higher surface temp as well. While the things you say can be true, it doesn't really apply to what we are discussing.
In this case he's not running the humidifier too much, he may not be running his dehumidifier enough (I'm not suggesting running it more, either to attempt to mitigate the issue, since that, IMO, is GENERALLY the wrong solution to this problem (even though it could work).
You are right ... a high space temp and running a humidifier all out with cold temps outside is a seriously bad combination. But this discussion isn't about someone making such a poor combination of decisions (setting aside that there may have been a very good reason for that person to do what would otherwise be considered a very stupid thing).
Moisture can be a funny science. The basics are easy/simple to learn/understand, but the actual results can be mired in complex interactions of factors. As you say ... To know how the science works, it helps to (i) live in it (ii) study and think about what you experience, and (iii) try to make sure you think of all the factors involved. Couldn't agree more.
QUOTE
In this case he's not
QUOTE
In this case he's not running the humidifier too much, he may not be running his dehumidifier enough (I'm not suggesting running it more, either to attempt to mitigate the issue, since that, IMO, is GENERALLY the wrong solution to this problem (even though it could work).
You are right ... a high space temp and running a humidifier all out with cold temps outside is a seriously bad combination. But this discussion isn't about someone making such a poor combination of decisions
END QUOTE
I can find nothing in the thread which suggests or states whether the customer is using a humidifier.
He stated a problem giving minimal information - among other responses of possible causes, I mentioned the possibility of running high temps and high humidity.
I still maintain that it is a possible explanatioin given the limited information provided,
And I get the impression you are assuming information in "rebutting" my suggestion (which you now seem to actually accept.)
The OP did say "Their
The OP did say “Their dehumidifier is running in the basement.” I have to assume that he wasn’t also running an uncontrolled humidifier at the same time. So, you are absolutely right, there is “nothing in the thread which suggests or states whether the customer is using a humidifier.” It’s just the opposite.
I was primarily having a general discussion of the science that had some relation to the OP’s situation while realizing there was a lack of sufficient detail to really determine anything specific or be able to suggest any solution. More food for thought than anything (hopefully relevant food).
I don’t disagree with your statements of science. I got the feeling that you digressed from the specific situation that was being discussed.
>> The OP did say "Their
>> The OP did say “Their dehumidifier is running in the basement.” I have to assume that he wasn’t also running an uncontrolled humidifier at the same time.
You have more faith in human nature than I do, I guess.... {G}
In my experience doing home inspections and often talking to people about humidifiers on furnaces, I've found that many don't have a clue as to hows and whys.
It is very common for me to find them set fairly high during summer, and very few have ever understood what the sheet metal "gate valve" (real name????) is for.
In fact, it is not uncommon to see humidifiers set "right" during the winter with the gate shut
Points well taken. But assuming for no particular reason that the OP doesn't know the difference between a humidifier and a dehumidifier is a bit of a leap I think. Unless the poster has given us a hint at his lack of 'human nature', I think we have to give him the benefit of the doubt and assume that he has expressed his situation reasonably accurately. I don't think we should arbitrarily second guess what he says and assume he is describing a condition just opposite of what he says.
Not a pro here, but I would like to suggest rather than a light, get one of those warming bars than they put in pianos to keep them from getting to moist and changing tune. Very low energy use and it would keep the closet warmer and thus less likely to have condensation
Yeah, that would be safer than a light bulb. But of course a watt is a watt in terms of heat.
Another thing that could contribute to lowering the surface temperature of the wall in the closet is that often stuff gets pushed up against the wall. This could be just a rack of clothing or bags of unused stuff. Either way, stuff in general up against the wall adds insulation to the assembly without providing a vapor barrier to keep the room humidity off the now colder surface.
OTOH, for a problem closet a simple solution (though a minor code violation and kinda ugly) would be to glue foam board to the back wall. Two inches of foam would generally make a significant difference.
Many wouldn't consider that a
Many wouldn't consider that a 'minor' code violation. Albeit not an immediate safety hazard, if there was to be a fire, would it only be a minor fire? :o)
Depends on what else is stacked against the back wall.
If one were concerned about the fire issue the foam could be covered with drywall easily. Just caulk the seams and maybe slap on some paint if you're really being picky.
Good point and not to unusual to see storage items stacked against the wall which will quickly exacerbate the problem.