OSB mold?

[volaredon]

my garage was built in 06 and we used all OSB underlayment for the walls and the roof and no issues
in 2009 I re roofed my home and had to do alot of wood replacement.
I again used 3/4" OSB. But, on the house on the underside ("attic side") it appears to be molding... ********* spots but none on the remaining original tongue and groove planking
and on the house I went with a steel roof vs shingle on the garage (when it needs redone the garage will also be roofed with steel)
I dont get it.... bad batch of OSB when I did the house?
The only thing I know to do with it now (another tearoff is out of the question) is to go up there this Spring before it gets too hot outside and paint the whole underside of that OSB with Kilz....
it does seem worst on the west hip, further down I see no evidence of it
On the west side of the house ("L" shaped ranch, west side has short leg of the "L" )I went down to bare rafters as I had to replace several of them to correct an idiot move from when the house was built, I replaced all the underlayment on that end; and this is where the apparent mold is worst over the attached (unheated) garage

any idea on why this may be? I also replaced the soffit the Po had just laid new soffit over old plywood soffit without adding vents;
I put the steel soffit up after pulling the plywood out and I put vented soffit every other piece instead of every 3rd as was recommended; I added a ridge vent and replaced my power vent as well with another.
I am thinking I gotta add another power vent on that short leg of the "L"

any thoughts from the peanut gallery?

 

[tomroblee]

I can't explain your problem, but having both a ridge vent and power vent may be part of your problem. The roof vents (whether power or not) need to pull air from the soffit vents. The power vent may be pulling air IN the ridge vent and leaving the rest of the air in the attic relatively stagnant.

Some further information might help the experts. Where are you located? How old is your house? Is there a vapor barrior under the insulation in your attic? Is there adequate room for the air from the soffit vents to get into the attic or is the flow or air blocked by attic insulation?

Is the "free air" area of your soffit vents adequate? A lot of the perferated metal and vinyl soffit materials only have about one square inch of free air flow per square foot of soffit material. If you have fairly narrow soffits, this doesn't provide much air flow.

 

[volaredon]

I can't explain your problem, but having both a ridge vent and power vent may be part of your problem. The roof vents (whether power or not) need to pull air from the soffit vents. The power vent may be pulling air IN the ridge vent and leaving the rest of the air in the attic relatively stagnant.

Some further information might help the experts. Where are you located? How old is your house? Is there a vapor barrior under the insulation in your attic? Is there adequate room for the air from the soffit vents to get into the attic or is the flow or air blocked by attic insulation?

Is the "free air" area of your soffit vents adequate? A lot of the perferated metal and vinyl soffit materials only have about one square inch of free air flow per square foot of soffit material. If you have fairly narrow soffits, this doesn't provide much air flow.

my house was built in 1965. I am an hour south of chicago,
and as compared to the previous soffit put directly over plywood by a PO, there has gotta be much more airflow than before. (they didnt add any vent caps or grilles or even cut out any og teh old plywood soffit before slapping the aluminum over the top)
Last winter my power vent died (damn china ****) and I replaced it in the spring; it was about the same time I discovered the dead power vent that I 1st discovered the black spots, and the rest of the roof around the area of the power vent and towards the other end of the house doesn't have this problem thats why I was thinking I may need to add a 2nd one.

 

[volaredon]

also I have a small ventless nat gas wall mount heater that I am gonna be hooking up this week just enough to take the chill off out there so the back half of the house itself isn't so cold; my family room is right behind this attached garage
I re sheated the walls that adjoin the house with OSB as well as the ceiling out there and insulated it heavily plus put an OSB subfloor above the garage for storage space.
Last winter for the 1st time ever, on the 2-1/2 sides that do not adjoin the house, I had frost on the ceiling out there (also OSB) about 2 ceiling joists wide along the walls (but not on the walls and not on the subfloor just above this ceiling either in the attic)

 

[buddyboy]

The power vent may be pulling air IN the ridge vent and leaving the rest of the air in the attic relatively stagnant.

it's great that you added the soffit vents where none existed before but like tomroblee suggested air probably isn't moving through those vents enough to make a difference.

you can always test it by firing up those power vents, then go outside and use a smoke gun or piece of Kleenex to see if it gets sucked up to the outside soffit vents.

then block off the power vents and repeat test only relying on the ridge vent to exhaust.

then finally IF you can block off the ridge vent, and use only the soffits as input air and pwr vents as exhaust air, repeat test.

go with what you think is best.

but it is best practice to NOT use ridge vents with pwer vents because what tomroblee suggests happens 99% of the time

 

[volaredon]

I can probably stuff some insulation into the ridge vent or something like that...
it seems that since only the short leg of the "L" is the only part doing this, furthest from the power vent.... but also as was said this part of the house was also previously uninsulated on top of being unheated..... i wonder if this may have something to do with it.... now how bout my idea to paint this area that can be reached from the attic with KILZ????? Not for appearance sake (I dont spend any more time in attic than needed) but to seal/kill this if it is what I think it may be?

Also as was said it seemed to initially show up while my power vent was not working....

but I aint an expert either so that's why I was asking

 

[BWS]

Hard to say?

The first thing I'd do after determining which way prevailing winds blow,and their effect on venting...and how the Sun is affecting the roof(understanding the different seasons,and how the roof is dissapating this heat/cold.

As posted above,I would be doing a check with smoke,looking for some kind of ideas on venting effectiveness.Prolly take a temp gun up and shoot some numbers as well.Google-foo,HVAC "balancing"....not a direct answer,but should give a little background on certain air movements.Good luck.

 

[hockey88fan]

The ventless nat gas heater you're planing to hook up may add to the problem.

 

[TheShrine]

.... now how bout my idea to paint this area that can be reached from the attic with KILZ????? Not for appearance sake (I dont spend any more time in attic than needed) but to seal/kill this if it is what I think it may be?

First of all you fix the reason you have the problem. There have been some excellent suggestions here. Air flow/exchange is a big issue in attics. OSB is not your problem. "Stachy or Black Mold" will grow on almost anything if the conditions are right. Be glad you don't have Sheetrock up there! It's "stachy" food! As far as the KILZ goes...no, it will not help. It will not kill mold and the last thing you want to do is cover/hide it. It has been my experience that there is usually a lot more mold than you can see. The ideal conditions for mold is dark damp locations ie. inside walls and attics. A homeowner will usually address a "damp" condition that is seen. It is those areas that we don't know about that result in excessive mold. Very small areas can be cleaned w/ bleach or like chemicals but those are topical. Again, those are topical cleaners. Stachy/ Black Mold does not like to be "seen" and grows WILDLY in areas you can not see until........get ready for this....remediation. Basically, that means removing all of the structure that has mold on it and topically treating all of the surrounding area.

The degree of your problem will dictate your approach but merely covering it will disappoint you. Your post indicated that this might have started after an '06 structural change.....that's 6+ years of opportunity of growth and you're just "seeing" it now. If you decide to look into this I'd suggest you inspect your A/C vent system. If mold is in fact in your attic ( for 5+ years) it is probably in your A/C vent system.

With that to consider, I hope yours is topical and can be cleaned w/ a good bleach scrubbing.

 

[JakeKohl]

Attic venting is not terribly complicated but there is a lot of mis-information out there and simple installation issues can lead to big problems. For starters, if you have a ridge vent, you must have adequate (a LOT) of sofit vents. You need air flowing from the bottom of the attic to the upper level to take advantage of the natural air current provided by a ridge vent. If you have a ridge vent with gable vents and inadequate sofit vents, the air just flows from the gable through the ridge and doesn't move any sizable amount of attic air and you get moisture buildup and mold growth - this configuration is actually worse than just having gable vents alone because it short circuits the flow you would normally get between gable vents.

I've tested the ridge vent with my new garage vs. the powered vents I have on my house. My powered vents move more air and keep the attic temps lower than the ridge vent does and because of that, I'm sticking with the powered vents with gable and limited sofit vents on the house (new roof coming soon). There is a reason why you'll have a hard time finding a ridge vent on a house in Florida - they simply don't work well in some climates and they don't manage heat build up very well. If the wind blows in one direction more than another, it can also totally cancel out much of the ridge vent's effectiveness. If you just want to keep the air moving and moisture controlled, go ridge vent with TONS of sofit vents (vent the entire sofit) so even the sofit vents can vent from one side to the other if the wind is perpendicular to the ridge vent. If you want to control the temperature in the attic and control moisture buildup, use powered ventilation.

OH, and PS - make SURE your bathroom vents are plumbed through roof fixtures so they expel air to the outside through the roof sheathing to the outside. If you vent them through the sofit, the new ridge vent may actually be pulling moist expelled air back into the attic.

 

[volaredon]

First of all you fix the reason you have the problem. There have been some excellent suggestions here. Air flow/exchange is a big issue in attics. OSB is not your problem. "Stachy or Black Mold" will grow on almost anything if the conditions are right. Be glad you don't have Sheetrock up there! It's "stachy" food! As far as the KILZ goes...no, it will not help. It will not kill mold and the last thing you want to do is cover/hide it. It has been my experience that there is usually a lot more mold than you can see. The ideal conditions for mold is dark damp locations ie. inside walls and attics. A homeowner will usually address a "damp" condition that is seen. It is those areas that we don't know about that result in excessive mold. Very small areas can be cleaned w/ bleach or like chemicals but those are topical. Again, those are topical cleaners. Stachy/ Black Mold does not like to be "seen" and grows WILDLY in areas you can not see until........get ready for this....remediation. Basically, that means removing all of the structure that has mold on it and topically treating all of the surrounding area.

The degree of your problem will dictate your approach but merely covering it will disappoint you. Your post indicated that this might have started after an '06 structural change.....that's 6+ years of opportunity of growth and you're just "seeing" it now. If you decide to look into this I'd suggest you inspect your A/C vent system. If mold is in fact in your attic ( for 5+ years) it is probably in your A/C vent system.

With that to consider, I hope yours is topical and can be cleaned w/ a good bleach scrubbing.

not quite. the detached garage was built in 06 no mold there.
the house roof was done in fall 09. problem 1st noted (suspected) in Spring '12 at same time as burnt out power vent was discovered. NO suspected mold was seen up there before the dead power vent. I have a counterflow furnace so I have a return duct in the attic but my "feed" vents are in the crawlspace where I have noticed NO mold at all. (YES I have been down there and YES I have been watching for it there)
like I (thought I) said it is pretty much confined to the west hip so far

 

[volaredon]

Attic venting is not terribly complicated but there is a lot of mis-information out there and simple installation issues can lead to big problems. For starters, if you have a ridge vent, you must have adequate (a LOT) of sofit vents. You need air flowing from the bottom of the attic to the upper level to take advantage of the natural air current provided by a ridge vent. If you have a ridge vent with gable vents and inadequate sofit vents, the air just flows from the gable through the ridge and doesn't move any sizable amount of attic air and you get moisture buildup and mold growth - this configuration is actually worse than just having gable vents alone because it short circuits the flow you would normally get between gable vents.

I've tested the ridge vent with my new garage vs. the powered vents I have on my house. My powered vents move more air and keep the attic temps lower than the ridge vent does and because of that, I'm sticking with the powered vents with gable and limited sofit vents on the house (new roof coming soon). There is a reason why you'll have a hard time finding a ridge vent on a house in Florida - they simply don't work well in some climates and they don't manage heat build up very well. If the wind blows in one direction more than another, it can also totally cancel out much of the ridge vent's effectiveness. If you just want to keep the air moving and moisture controlled, go ridge vent with TONS of sofit vents (vent the entire sofit) so even the sofit vents can vent from one side to the other if the wind is perpendicular to the ridge vent. If you want to control the temperature in the attic and control moisture buildup, use powered ventilation.

OH, and PS - make SURE your bathroom vents are plumbed through roof fixtures so they expel air to the outside through the roof sheathing to the outside. If you vent them through the sofit, the new ridge vent may actually be pulling moist expelled air back into the attic.

I dont have a Gable roof but rather a hip roof; I am not sure if that changes anything you say here... my bath vent is run up to within a foot of the power vent no mold noted anywhere near the powervent or other end of house.

 

[joshmodelskidoo]

Did you put tar paper or something between the wood and steel to prevent condensation build up? Heat loss to a cold attic causing condinsation maybe? Sounds to me like you well vented.

 

[volaredon]

The ventless nat gas heater you're planing to hook up may add to the problem.

huh really? I thought warming it up out there to keep things "dried out" might help instead of hurt;

scrub with bleach between about 12 rafters all the way from the sill to the king rafter on my back... hoo boy. It hasn't "layered" if that means anything, it isnt a thick buildup at all.

 

[volaredon]

Did you put tar paper or something between the wood and steel to prevent condensation build up? Heat loss to a cold attic causing condinsation maybe? Sounds to me like you well vented.

Yes I did tar paper this was a total tearoff at the time, and I did get caught in rain with no tar paper or roofing and had to go up there in the rain and tarp my whole house while trying very hard to keep from sliding off ala biggie size Slip n Slide.... and then nail wood lath cleats plus hang gallon bottles full of water from all the tarp's tiedown grommets for acouple days til the rain stopped; I was largely on my own for this project and like I said i replaced a lot of wood; rafters and sheathing both... help was hard to come by... I started on a Tuesday knowing a big storm was coming Sunday (boy did it ever) and that Sunday was spent tarping... for wood replacement, papering, metal roof installation plus soffit and fascia (all fascia wood was replaced 100%, soffit was torn out totally as was original plywood soffit covered up by whoever applied the alum soffit sometime before i bought the house in 1998....
after that rain storm I did get myself some help finally; but my roof, soffit and fascia wound up taking like 6 weeks start to finish. It dont help that I was 2 years removed from a chain saw accident that had me on Disability; I very nearly lost my right foot above the ankle so I wasnt moving as fast as I had been able to do so previous to that, especially being up on a roof. Basically anything to get the job done reasonably (couldnt have afforded to hire it out even if I wanted to, which I didn't) without getting hurt again (it took forever to pay them hospital bills didnt want a repeat) so i was going SLOW

the (apparent) mold is only above the unheated garage that I insulated and re sheated in fall of 2010; following that with OSB subfloor above that garage over the newly insulated ceiling>>> the rest of the house attic is (and was before I bought the house) heavily insulated, with no subflooring on top of the insulation in the rest of the house (and no mold) there is also no mold on the subfloor OSB, below that part of the attic where I am seeing it (or what I think may be mold)

but as I thought I had said somewhere in here, last winter I saw frost on the garage ceiling, along all 2-1/2 walls of the attached garage that DON'T adjoin the house about 2 ceiling joists wide.... never seen that before.
Prior to my sheating the attached garage and insulating the garage was drywalled and had a few holes in the ceiling from "fall thru's" (No no one fell to the concrete garage floor, but a foot or 2 went thru that ceiling a time or 2
and it seemed people somewhere along the line liked storing stuff between the joists drywall isnt meant to carry any weight. .... re sheathing that garage and insulating I am sure affected the airflow up there....
I put in a closet out there for our extra clothes in '11, in that garage the whole length of the North wall (the only wall that completely adjoins the house);
I painted the closet ceiling with latex paint, (closet walls painted too, inside and out/ no paint damage to any of that though; we used regular interior wall paint but not the cheap stuff either) and had a square the size of width of the closet on the ceiling, at the west end that turned liquid and dripped, from moisture on the ceiling as described otherwise in this post/// the west wall is totally an outside wall.
that frost/moisture I mention, was only on the garage ceiling along the west, south and portion of the east wall that did not adjoin the house; I noted none of this in the family room behind the garage or on the garage walls;
the family room is heated, ceiling insulated heavily, and drywall instead of OSB meaning it would have surely fallen if it got any dampness....

I ONLY ever noted the dampness/frost on the attached garage ceiling LAST winter and at that, only when outside temps were in the mid teens or below... I am guessing coinciding with when the power vent died (but I didn't yet realize it was dead) My thoughts are that the dead power vent contributed to this, and that this was also when the suspected mold was first noticed.yes I ahve been up there many times in between and would have noticed it then if it was there since it's right where my pulldown attic stair and arric light, are at.

That tells me that the ridge vent isn't up to the task by itself. The current power vent is on the back (north) roof face, about the middle of the roof lengthwise, and is larger than the one I removed initially when I did the roof.
I only replaced the old one because of evidence of 4 layers of shingles under the old power vent mounting, not knowing its age and figuring a new one would be preventive maintenance at that point.

never ever seen this out there in the winters before last, and not so far this year though we have had a few nights that cold so far
We are expecting a run of nights that cold the beginning of next week.

I am up for most any solution short of the "Remediation" seen above because that means tearing that whole west hip down to bare rafters again.... I am not up for that idea.
If I gotta get up there in Spring before it gets too hot and scrub, so be it; but I still want to apply some KILZ or a similar product afterwards If not that, is there any coating that will kill it, seal it and prevent its return?
They did have packets hanging on a peg mear KILZ when I bought it that claimed to be mildewcide that said to dump and mix into paint I bought a couple packets of it. I have not applied any paint or other product up there as of yet.

this is all I can think of at the moment I hope it is all helpful info, towards helping come up with a solution and not "muddying the water"

 

[cabranch47]

Did you fasten the metal roof directly to the sheathing or did you strip it first and fasten the metal to the strips. I always thought that you had to strip it first to provide ventilation under the metal roofing to prevent condensation on the underside thus causing rot and mildew, ect. Just a thought. Good luck.

 

[tomroblee]

I still don't see any clear answers, but can offer a few comments.

You say that you are installing an unvented gas heater. One of the problems with unvented gas heaters is that they dump a lot of moisture into the air. Gas is a hydrocarbon (hydrogen and carbon atoms). When gas burns, the byproducts are carbon dioxide, carbon monoxide, and water.

You mention that you noticed that your powervent failed in cold weather. In most situations that I have seen a powervent is connected to a thermostat. It isn't intended to run in cold weather.

You indicate that you noticed frost in the garage (walls and ceiling) after you did your work in the garage. I would suspect that part of the reason that you noticed the frost was that you sealed up the garage to a significant degree---thereby trapping moisture inside. When the walls and ceiling cooled to below the dew point the water would condense on the cold surface. When the temperature dropped low enough, the condensed moisture would freeze into frost. Were there any changes in you house or lifestyle that introduced more mositure or water into your garage about this same time?

I'm somewhat puzzled about you discussions of the dead powervent. It sounds like you are saying that a previous owner had installed a powervent in the attic to exaust air----but there was no source of intake air into the attic other than possibly through the holes in the garage ceiling.

It sounds like you have (or did have) a moisture problem in your garage. The fact that the mold in the attic is directly above the attic access panel in garage suggest that the overly moist air in the garage was escaping into the attic through the access hole and condensing on the underside of the roof directly above.

You mention KILZ paint quite often. I don't think that the paint is meant to kill mold ormildew. It is meant to "kill" a stain (keep the stain from bleeding through new paint. It sure sounds like you have a moisture problem of some sorts. I think that you need to worry about killing the moisture problem. Once it is gone, the mold or mildew won't be an issue.

 

[volaredon]

there was a powervent in the house ever since I moved in I am guessing its been there since the house was built in 1965 I replaced it when I re roofed the house in 2009 because the old one had evidence of 4 colors of shingles in/around it; I thought I was being proactive in replacing it while I was in there. Preventive maintenance. the replacement I bought had a made in China motor (THAT pissed me off since the box was marked made in USA. that power vent lasted about 2 years. It had a thermostat and humidistat in its control box. the old original one I had also occasionally ran in winter too but not as often as this one; I replaced the 2009 power vent in spring of 2012 with an identical one so i could replace just the motor and not the whole housing etc because that would require me pulling up my metal roof panels if I had to replace anything beyond the motor. I have the humidistat and teh thermostat dials set to the power vent manufacturers suggestions (marked on box) I am guessing it is the humidistat making it run this time a year not the thermostat function. It was suggested when I did the roof job that I put the ridge vent in (sales people I bought the materials from and the local building inspector too) There was no frost on the walls out there just the ceilings abutting the outside walls but not adjacent to the walls that adjoin the house.

being that the family room was always colder than the rest of the house, that shares its north wall as being the garage's south wall, I insulated the garage including all the outside walls to try to keep that back family room warmer
this wall shared with teh family room is the area of the old garage that I built the closet along. there is 1 louvered door on the south wall of the closet and an opening for another louvered door on the east side, I have it but just have not gotten around to installing it.
Before I built my detached garage this was my workshop and I had several different types of heaters out there that I ran only when I was working out there. When I warmed the garage the back of the house was noticeably warmer. so the thought was to try to keep what heat I did have from escaping and that may help the family room stay warmer. Did I seal it too well? my thoughts were to plumb this ventless heater in to keep the chill off that garage (its the smallest one you can get IIRC) I have a gas line available very close to where I want to mount this heater in the crawlspace very little work needed to make the connection there. Back when I worked in that garage (it is glorified storage now) Iat one time or another I had a salamander (torpedo) out there or one of a few different varieties of propane heaters out there at one time or another; the "library stool" shaped propane heater, the "construction site" propane heater among them.... since I have my big garage now, I do very little work out in the attached garage any more so rarely heat it... but as huge a difference as any amount of heat in that garage made in the comfort in the house I figured it would be good to add this small ventless deal, just to run during the coldest of the cold for sake of not hearing my wife or son complain about that part of the house being cold. the attached garage is about 520 sf, rest of house that is heated is about 1300 sf; we had talked of turning this attached garage into our family room and then the existing family room then becoming the master bedroom but those plans are quite a ways off if they do happen.

Yes I mentioned Kilz a few times as I thought that product sealed and killed mold and mildew. yes I know I gotta solve the issue 1st before that will help I never intended that as a cure all.... but I thought that once I got that done, this would prevent spreading and kill off what is presently there. It ain't that bad yet (I know any mold is bad) but there are 2 homes in my neighborhood down around the corner from me, with elderly women living in, that I have done yard work and odd jobs for; both of these are side by side, drywalled attached (probably unheated like my attached garage) and both of their garages are like a huge scince experiment with terrible mold. I want to stem the tide and get mine remedied before it gets any worse; I do not care about "prettying up" the attic just want to seal things to kill whats there and keep it from spreading.

 

[volaredon]

Did you fasten the metal roof directly to the sheathing or did you strip it first and fasten the metal to the strips. I always thought that you had to strip it first to provide ventilation under the metal roofing to prevent condensation on the underside thus causing rot and mildew, ect. Just a thought. Good luck.

it is directly on the tarpaper which is directly on the sheating, of that was the problem, then the mold would not be confined to one hip of the roof/ it would be the a problem with entire roof. About 2/3 of my sheathing is still the original tongue and groove "1-bys", I used OSB for any thing that needed wood replacement. and there is NO hint of mold on that, including the east flank of the roof over this same garage.
Actually they suggested a 1/4" "fanfold" insulation between the sheathing and the metal in the literature I got from the lumberyard, but was told elsewhere in the same paperwork that it was perfectly OK to pit the metal directly on like I did
that fanfold stuff is basically 1/4" foam board; I would think that would aggravate a mold issue?

 

[volaredon]

XIt sounds like you have (or did have) a moisture problem in your garage. The fact that the mold in the attic is directly above the attic access panel in garage suggest that the overly moist air in the garage was escaping into the attic through the access hole and condensing on the underside of the roof directly above.
.

I hope youre right in the part of your comments that say (or did have)

 

[hockey88fan]

huh really? I thought warming it up out there to keep things "dried out" might help instead of hurt;

scrub with bleach between about 12 rafters all the way from the sill to the king rafter on my back... hoo boy. It hasn't "layered" if that means anything, it isnt a thick buildup at all.

Ventless gas fireplaces lead to an increase in the room's humidity. Burning gas or propane creates water vapor that can build up in a room and possibly lead to mold and mildew growth. You'd want to go with a vented model if possible.

 

[volaredon]

so if I run it long enough to warm the area and dry the air won't that take care of the moisture from the ventless? I am not looking to run it 24/7 but when its <20* outside at least.... like I had said, we don't work out there much (but we do "some") but as heat is drawn to cold areas making the back part of my house cold
one thing to add is that nothing has changed since last year but we have had some cold (<15*F) overnite lows so far this year and no frost like last year on the ceiling.... cant figure out what may be different this season? Monday the HIGH is supposed to be 18-20 all day, so I will see what happens if the ceiling again frosts up.... I have all the fittings and hardware but haven't had the time to hook up that heater.
When I moved in here 15 years ago, snowdrifts would form inside that garage at the man door and between the 2 overhead doors. I did fix that the 1st Spring I lived here.... new trim around the garage door frames and a new man door and frame to solve that issue.
but what ever has caused the frost on the ceiling and the apparent mold in the attic, is a new problem that has manifested since the start of last winter we have had alittle bit of cold last year and so far this year but still we are in the midst of our 2nd mild winter in a row. we have had some bad winters since I have been here without these problems....

 

[tomroblee]

Burning a 30,000 btu propane heater is going to create two to three pints of water per hour of burn time. It's a similar situation for a kerosene heater.

Running a heater will heat the air, but it will "dry" the air only to the extent that warm air can hold more moisture than cold air. Think of how an air conditioner drips water. When you cool the air, it can hold less water. When you heat air, it can hold more water.

 

[volaredon]

my detached garage floor likes to sweat. when I run heat out there everything stays dry, to date I have primarily used the kerosene torpedo out there; but I cant afford to feed it kerosene so I just heat it when I work out there... since heating that garage seems to alleviate the sweating I thought the same for the attached garage only the moisture I have described above is never on the concrete in the atatched garage (above which is where this suspected mold is) just this one past winter and just on the ceiling as described earlier.