Looking for suggestions on my newly built pole barn mold problem. I build a 32x48x12 pole building 2018 Spring. 2ft vented soffit on eaves, and 1ft vented soffit on gable ends with a ridge vent. I finished the inside this winter..closed cell spray foam walls Finished with pine tounge and groove and OSB 3ft up (for future metal wainscot). The ceiling is vaulted and is insulated with R-38 kraft faced batts and finished with white liner steel. I’ve noticed since I finished the inside that the windows were condensating this winter when it was really cold here in Michigan. As spring rolled around windows weren’t condensating so I thought I was good..but as I looked on the bottom 3ft of my walls inside I have random patches of fuzzy mold. I pulled the OSB off the wall and it’s clean on the backside, only coming from the inside of the building. Do I need to invest in a good dehumidifier? I’ve attached a picture of the Mold on the OSB..it’s not on the pine tounge and groove. Just on the bottom 3ft of the barn. Please help!
!HELP! Pole Barn Mold
- Thread starter Lewit12
- Start date
Marctrees
Well-known member
I think maybe - It is from condensation on OSB due to the insul in the wall not being thick enough to keep the dew point of the OSB high enough to avoid condensation on it's surface.
That could have made your surface of the OSB a "Condensation plane"
I'll bet your walls have too thin of foam.
Tell again exactly how walls were done.
I am not saying I KNOW this is your problem, but if you do not have sufficient wall insulation you need to look into it.
As a separate issue... did you park cars in and out bringing in snow/ ice that contributed to high humidity in the building ?
Marc
That could have made your surface of the OSB a "Condensation plane"
I'll bet your walls have too thin of foam.
Tell again exactly how walls were done.
I am not saying I KNOW this is your problem, but if you do not have sufficient wall insulation you need to look into it.
As a separate issue... did you park cars in and out bringing in snow/ ice that contributed to high humidity in the building ?
Marc
ddawg16
Well-known member
What insulation do you have in the walls and do you have a vapor barrier?
It could be as simple as painting the OSB....assuming you have insulation and vapor barrier
It could be as simple as painting the OSB....assuming you have insulation and vapor barrier
Marctrees
Well-known member
Condensation Control: Condensation can occur
inside a building when interior surface
temperature is lower than the dew point of the
inside air. Insulation thickness to control this
condensation must be based on the design dew
point and the design exterior ambient temperature.
inside a building when interior surface
temperature is lower than the dew point of the
inside air. Insulation thickness to control this
condensation must be based on the design dew
point and the design exterior ambient temperature.
Marctrees
Well-known member
HMMMM......
I dunno then.
But it still comes back to the mold should not be there unless enough moisture was there...from condensation.
So, WHY you are getting condensation w an apparently well insulated wall I don't know.
Need someone knowledgeable on this stuff... hopefully will chime in.
Marc
I dunno then.
But it still comes back to the mold should not be there unless enough moisture was there...from condensation.
So, WHY you are getting condensation w an apparently well insulated wall I don't know.
Need someone knowledgeable on this stuff... hopefully will chime in.
Marc
SGKent
Banned
Maybe lay something on the floor for a few days and see if moisture is on the backside.
Are you in an area that snow piles up against the building? Running any kerosene heaters in the building during cold weather?
Are you in an area that snow piles up against the building? Running any kerosene heaters in the building during cold weather?
Building is protected from snow piling up, I did run a torpedo heater on occasion this past winter knowing that was putting moisture into the building, I didnt run it often as the building holds heat well. I should check if my cement slab is putting out moisture
Marctrees
Well-known member
These random mold locations...
Maybe something was against the wall in those "Random" spot while you were heating ?
Marc
Maybe something was against the wall in those "Random" spot while you were heating ?
Marc
Condensation needs 2 things to form, moisture and a difference in temperature. The more you have of one thing, the less you need of the other. So if there's a bunch of moisture in the building, even a temp difference of a few degrees (F) can be enough for condensation to form on the cool surfaces.
Sounds like you're not conditioning the space regularly, and when you are you're adding more moisture with the torpedo instead of removing it with another heat source. And of course that's the worst time to add moisture as it's the time when the temp difference is greatest between interior and exterior.
Sounds like you're not conditioning the space regularly, and when you are you're adding more moisture with the torpedo instead of removing it with another heat source. And of course that's the worst time to add moisture as it's the time when the temp difference is greatest between interior and exterior.
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I think if you measure the relative humidity .............you will find it’s running over 70%.
At that high level of moisture in the air any organic material like wood, rubber, paper or fabric will attract and grow mold and mildew.
In my case I have a conventional stick built very well insulated garage 1000 sqft. The mold was first notice on my leather welding gloves. My humidity levels were 75-80%.
The fix was a large dehumidifier and the humiliation levels dropped to 40-50% in two days.
The good news it sounds like your building is well sealed. There are dozens of post on the humidity and mold issues. Most are not solved because the buildings are not sealed or insulated. If you don’t have control of the air exchange rate and insulation there’s is little chance of controlling the humidity as your building would follow every weather front. Not to mention the cost of running dehumidifier only to leak the conditioned air.
These stand alone garages often act like a basements in the northern climates when it comes to humidity and condensation.
Current condition in my shop are 54%. My target is 50% and the Dehumidifier was off over night ( shut down for noise control last night while working and not turned back on).
At that high level of moisture in the air any organic material like wood, rubber, paper or fabric will attract and grow mold and mildew.
In my case I have a conventional stick built very well insulated garage 1000 sqft. The mold was first notice on my leather welding gloves. My humidity levels were 75-80%.
The fix was a large dehumidifier and the humiliation levels dropped to 40-50% in two days.
The good news it sounds like your building is well sealed. There are dozens of post on the humidity and mold issues. Most are not solved because the buildings are not sealed or insulated. If you don’t have control of the air exchange rate and insulation there’s is little chance of controlling the humidity as your building would follow every weather front. Not to mention the cost of running dehumidifier only to leak the conditioned air.
These stand alone garages often act like a basements in the northern climates when it comes to humidity and condensation.
Current condition in my shop are 54%. My target is 50% and the Dehumidifier was off over night ( shut down for noise control last night while working and not turned back on).
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I think if you measure the relative humidity .............you will find it’s running over 70%.
At that high level of moisture in the air any organic material like wood, rubber, paper or fabric will attract and grow mold and mildew.
In my case I have a conventional stick built very well insulated garage 1000 sqft. The mold was first notice on my leather welding gloves. My humidity levels were 75-80%.
The fix was a large dehumidifier and the humiliation levels dropped to 40-50% in two days.
The good news it sounds like your building is well sealed. There are dozens of post on the humidity and mold issues. Most are not solved because the buildings are not sealed or insulated. If you don’t have control of the air exchange rate and insulation there’s is little chance of controlling the humidity as your building would follow every weather front. Not to mention the cost of running dehumidifier only to leak the conditioned air.
These stand alone garages often act like a basements in the northern climates when it comes to humidity and condensation.
Current condition in my shop are 54%. My target is 50% and the Dehumidifier was off over night ( shut down for noise control last night while working and not turned back on).
What dehumidifier are you running in your shop and what size is your shop? Thank you
rakane
Well-known member
Watching for that answer. Looking for one that will drain outside, 40 x 60 shop.
Meanwhile is a 30' Grady White.
Meanwhile is a 30' Grady White.
Marctrees
Well-known member
Any and all dehumids can drain as far as one wants with an appropriate outboard aftermarket condensate pump.
Marc
Marc
I use a BIG box store GE brand 70 pint direct hose drain to a floor drain.
GJ has many dehumidifier threads on quality and durability of dehumidifiers. I am 5 years on this unit, which seems to be average.
It has no trouble keeping up with my levels of humidity and the 1000 sqft. It turns off as the level is maintained. My shop building is 100% shaded by woods. Running the dehumidifier makes the shop “feel” like it’s air conditioned. As the shop temperature never gets over 75* no matter how hot it’s gets out side. The concrete slab never warms and act as a cooling unit. As stated early the building is very well insulated with R60 in the ceiling and 38 in the walls. Metal siding on the insides and conventional framing and siding out.
I my situation I only need to run the unit in the summer. Winter I heat the space to 50-55*. With the added heat the humidity levels are never an issue. Heating costs are barely noticed in winter estimated at $20 per month ( avg) with NG.
Obviously when conditioning the air, windows and doors stay closed as much as practical. If the outside temperature is 70* and relative humidity is 37% the doors could be open.
GJ has many dehumidifier threads on quality and durability of dehumidifiers. I am 5 years on this unit, which seems to be average.
It has no trouble keeping up with my levels of humidity and the 1000 sqft. It turns off as the level is maintained. My shop building is 100% shaded by woods. Running the dehumidifier makes the shop “feel” like it’s air conditioned. As the shop temperature never gets over 75* no matter how hot it’s gets out side. The concrete slab never warms and act as a cooling unit. As stated early the building is very well insulated with R60 in the ceiling and 38 in the walls. Metal siding on the insides and conventional framing and siding out.
I my situation I only need to run the unit in the summer. Winter I heat the space to 50-55*. With the added heat the humidity levels are never an issue. Heating costs are barely noticed in winter estimated at $20 per month ( avg) with NG.
Obviously when conditioning the air, windows and doors stay closed as much as practical. If the outside temperature is 70* and relative humidity is 37% the doors could be open.
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Picked up a Moniter today and stuck it in the barn and it’s readiing 80% humidity..I’ve had a humidifier in the barn for about 2days. I don’t know what size it is (it’s been running in my basement since I moved in) now I either need to find a big *** dehumidifier to keep up with 1500sqf of think of a different solution to keep that level down. Will a big box store dehumidifier really Keep up with that size building? Or do I need to find a commercial unit? The outside humity is 64 today.
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Marctrees
Well-known member
I am NOT thoroughly understanding of all the H, RH, dewpoint wet bulb dry bulb etc stuff at all.
Never interested me to learn that.
But I will say - It seems to me the dehumidifier is a band aid. solution... and there is some other underlying problem that needs to be discovered and solved.
Lewit - Did you do the taping poly to floor slab moisture test ?
If you know you have Poly under your slab you should be OK.
Do you KNOW you have poly under your slab and you are not in somekinda high water area ?
I Just don't understand why a vented building is getting mold.
Marc
Never interested me to learn that.
But I will say - It seems to me the dehumidifier is a band aid. solution... and there is some other underlying problem that needs to be discovered and solved.
Lewit - Did you do the taping poly to floor slab moisture test ?
If you know you have Poly under your slab you should be OK.
Do you KNOW you have poly under your slab and you are not in somekinda high water area ?
I Just don't understand why a vented building is getting mold.
Marc
I don’t have a vapor barrier under concrete. I will try the plastic over the concrete to see if that’s where the moisture is coming from. Should I pick a dry humity day and open up the windows and garage doors to air it out? Because the humitity is 20% less outside than in my barn currently
Marctrees
Well-known member
OK, so you have your slab directly on dirt.
Sorry, but never a good thing.
Do you have a situation where soil is wetter than usual like high ground water table or etc?
Drainage around building good ?
Gutters leading water away from building?
Google how to do a poly tape test properly. I'm not positive.
Marc
Sorry, but never a good thing.
Do you have a situation where soil is wetter than usual like high ground water table or etc?
Drainage around building good ?
Gutters leading water away from building?
Google how to do a poly tape test properly. I'm not positive.
Marc
Marctrees
Well-known member
I am frustrated by this thread not getting to a solution for OP.
It seems to me the mold is because of the high humidity inside the building.
SO, then... What are all possible reasons for this ?
Marc
It seems to me the mold is because of the high humidity inside the building.
SO, then... What are all possible reasons for this ?
Marc
Marctrees
Well-known member
So, I think you said building has natural convection venting... soffit and ridge ? yes ?
But yet humidity INSIDE is like always higher than outside ?
Seems to me to be something not normal ?
Marc
But yet humidity INSIDE is like always higher than outside ?
Seems to me to be something not normal ?
Marc
Marctrees
Well-known member
Did your foam sprayer FOR SURE not block the venting ?
AND, by your photo all that is vented at best is your area above ceiling, NOT the building below ceiling.
Marc
Marc
AND, by your photo all that is vented at best is your area above ceiling, NOT the building below ceiling.
Marc
Marc
Marctrees
Well-known member
So your building is in affect sealed other than door leaks etc.
So if your slab is passing water it has nowhere to go but accumulate in building.
Marc
So if your slab is passing water it has nowhere to go but accumulate in building.
Marc
Marctrees
Well-known member
No more yacking until you properly definatively check your slab for water infiltration.
Make sure you understand the difference of a slab sweating vs water coming through.
Totally different things.
Marc
Make sure you understand the difference of a slab sweating vs water coming through.
Totally different things.
Marc
Marctrees
Well-known member
Thanks for the help trying to get to the bottom of this..spray foamer just did the walls and didn’t block any venting. I insulated the ceilings with the Kraft faced batts. The batts left proper room for ventilation from eaves to vent.
Marctrees
Well-known member
Ok so your attic is vented... but not the building interior.
Properly do floor test in few places next step.
Marc
Properly do floor test in few places next step.
Marc
Daniel Dudley
Well-known member
- Joined
- Sep 4, 2009
- Messages
- 3,546
Put a second dehumidifier in the barn and have brought the humidity down from 81% to 67% since last night. It’s slowly going down, we will see if I can keep it around 55% or so once it gets down that low. I taped a couple squares of 4mil plastic on my floor last night and still see no moisture forming on the plastic. I will check back tonight and let you know
Marctrees
Well-known member
I do not know the details of exactly how to do the test.
Sure... I know you tape on a piece of poly.
But past that... like how temps or anything else can affect the results I don't know.
Make sure YOU know.... so you KNOW you end up w valid results.
Marc
Sure... I know you tape on a piece of poly.
But past that... like how temps or anything else can affect the results I don't know.
Make sure YOU know.... so you KNOW you end up w valid results.
Marc
Marctrees
Well-known member
I really think there is a DUHHHH simple answer to this problem... just need to somehow figure it out or find someone that KNOWS this stuff.
I would be Googling stuff like building envelope high humidity mold and such.
Marc
I would be Googling stuff like building envelope high humidity mold and such.
Marc
Marctrees
Well-known member
I'd be studying stuff like below hoping for an Aha!
Marc
https://www.google.com/search?ei=Y2...1......0....1..gws-wiz.......0i71.WmbByYNPtIs
Marc
https://www.google.com/search?ei=Y2...1......0....1..gws-wiz.......0i71.WmbByYNPtIs
Marctrees
Well-known member
Lewit - Whereabouts in MI are you ?
Some particularly humid area ?
Marc
Some particularly humid area ?
Marc
Marctrees
Well-known member
If your inside humidity is average higher than outside it would seem to me you need to vent the interior.
Maybe even just like good size gable end vents and somekinda low intakes.. natural convection.
A "Building envelope" Guy could answer this in a heartbeat.
Just thinking out loud.
Marc
Maybe even just like good size gable end vents and somekinda low intakes.. natural convection.
A "Building envelope" Guy could answer this in a heartbeat.
Just thinking out loud.
Marc
im About 10min from the shore of lake mi..I wouldn’t say my humidity is always higher than outside. It’s been a wet spring and seems to have high humidity with all the water we have gotten. Just need to dry things out inside the barn and keep them dry
I have gotten the humidity down to 50% with the dehumidifier. I’m not in the barn much in the summer time so it doesn’t get opened up to outside air often. I’m not sure if moisture came up from the slab when the frost came out of the ground this spring and that gave me the high humidity I was having and since the barn isn’t open much it couldn’t escape because it’s sealed tight? I had the poly tapped on my concrete slab for multiple days and didn’t have moisture under it. The was slab was poured on lots of fill sand. I haven’t had the dehumidifier off to see if the humidity would rise if not running.
Sorry but it’s critical to understand the terms and conditions of humidity.........so you can control it. Relative Humidity is “relative” to the temperature.
Example yesterday it was 75* and relative humidity was 38% during the day over night the the temp dropped 59* and RH was 83%. So yes, during the day opening and ventilation of the building would have been a good idea.....but......timing would be critical.
If you want effective humidity control you must control ( reasonable control) the temperature and air exchange rate of the building. If your controlling the air exchange, your not venting the building. Attic venting is not venting the building its venting the hot air in the attic.
Unless the building is sitting on spring and water is pounding on the floor the poly under floor is not an issue. Yes it helps, again it’s not critical or all that important in the grand plan.
If he stops running the dehumidifier the humidity level will slowly rise depending on the air exchange rate and the weather conditions. The indoor humidity levels will slowly float ........
Once the target humidity is reached.........it might not necessary to run two units.
As far as Michigan be humid........it’s not......at least not compared places like Corpus Christi or New Orleans. Michigan the humidity is variable as the weather.
When you see “you store it places” with climate controlled storage........it’s because you stuff will get ruined in consistent high humidity.
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SGKent
Banned
Since you are complaining (not in a bad way) about mold on the inside, and not all over the outside, it might be a safe assumption that the humidity problem is inside. I think you will need to add some venting to the building to keep the air circulating. There could be environmental causes such as the slab and water table, the building location like is it in a low spot where cold air collects etc.. Bringing more humid air across a cold surface would cause more moisture, but you can check differences in wall temp with an infrared temperature gun. Even a cheap one from Harbor Freight would give you an answer if the lower part of the wall is cooler. If it isn't then you probably will need to ventilate it and suffer the cold or heating bill, or you will need to condition the space or run the dehumidifiers. All that said, I bought a magnetic humidity and temp gauge on Amazon that tells me humidity in the house. Neat little device. Quite inexpensive.