Having a problem with condensation in my building which I thought was over once the concrete cured. Hoping someone on here can help with a solution. The building is 30 x 30 insulated with a insulated garage door. Went in yesterday morning an the building was covered in frost being it was cold outside but when I went in I noticed condensation around the inside side of door an on the garage door an also on each side of the ceiling joists on the white blanket insulation from where the insulation is screwed down tight to the joists. The building is not heated but is warmer than outside temps. There also is no ventalation in the building. What can I do? Thanks in advance..
Pole barn problem.....
- Thread starter wraiths
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Dr Dave
Platinum Member
Did you put a vapor barior under your slab? Is the insulation at the ceiling joist or the roof rafters? If the ceiling is insulated add vents for attic space, ridge and eve vents work the best. Also some, now install a vapor barior between tin and roof rafters, along with ceiling insulation.
JimRB
Veteran Member
Where do you live?
There are some solar convection current heaters some people use in their barns to warm them up. I have not seen wooden rafters get sweaty but my barn is well ventilated as it is a barn, not a shed/garage. I could see metal rafters getting sweaty.
Solar space heating -- active and passive solar projects for space heating
The Zen of Passive Solar Heating Panel Design
There are some solar convection current heaters some people use in their barns to warm them up. I have not seen wooden rafters get sweaty but my barn is well ventilated as it is a barn, not a shed/garage. I could see metal rafters getting sweaty.
Solar space heating -- active and passive solar projects for space heating
The Zen of Passive Solar Heating Panel Design
Dutch445
Elite Member
i have a 40x60 that came with the property i bought a year ago, and it is also insulated,
and the interior is finished in steel siding. i would imagine 16' ceilings.
it is basically storage for my camper trailer, boat, etc. last winter i noticed a lot
of condensation on the camper (steel siding) and other items in the barn, and i just
attributed it to cold temps and humidity. this year i have been running the ceiling
fans (2) and the last time i was out there i didn't notice any moisture. the windows in
this barn are far from new, and i know i get some air leaking thru.
i will look into the heaters though, my barn has awesome southern exposure up on top
of a hill.
and the interior is finished in steel siding. i would imagine 16' ceilings.
it is basically storage for my camper trailer, boat, etc. last winter i noticed a lot
of condensation on the camper (steel siding) and other items in the barn, and i just
attributed it to cold temps and humidity. this year i have been running the ceiling
fans (2) and the last time i was out there i didn't notice any moisture. the windows in
this barn are far from new, and i know i get some air leaking thru.
i will look into the heaters though, my barn has awesome southern exposure up on top
of a hill.
Zebrafive
Super Member
Do you have an overhang (eaves)? Is the ceiling insulation tight to the roof or did you leave an air space?
I think you need eave to peak ventilation above the insulation.
I think you need eave to peak ventilation above the insulation.
the old grind
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JimRB, thanks for the links. I'm gettin' ideas already ...
Wraiths your geography has a lot to do with what to expect from local weather variations. (won't insist you tell us where that is...) Warm days after a cold spell can leave barn contents sweating regardless of the floor's contribution. Ventless gas heaters add moisture, if you consider adding one later on. Unvented buildings can be troublesome moisture traps anywhere but the arid Southwest.
Guys, d'ja ever wonder if a powered gable vent would help if it was controlled by a humidistat but overridden as needed, say when heat is on?
Wraiths your geography has a lot to do with what to expect from local weather variations. (won't insist you tell us where that is...) Warm days after a cold spell can leave barn contents sweating regardless of the floor's contribution. Ventless gas heaters add moisture, if you consider adding one later on. Unvented buildings can be troublesome moisture traps anywhere but the arid Southwest.
Guys, d'ja ever wonder if a powered gable vent would help if it was controlled by a humidistat but overridden as needed, say when heat is on?
I thought about putting in a ceiling fan to help keep the air moving but wasn't sure if that would help or not. My building doesn't have any ventalation at all no windows either. What do you think would be better a ceiling fan or gable mounted fan or using a dehumidifier? Hate to go with dehumidifier since in the summer will be working in there with door up an that would be bringing in more humid air. By the way I'm located in s.c. so we do have humidity. So what would be the best fix is what I'm asking cause I don't have a clue. Would moving the air with a fan help or should I go with a gable exhaust fan. If gable fan is the best wouldn't it need a intake vent also thus bringing in fresh air and making the building the same temp as outside?
the old grind
Super Member
- Joined
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- Mid-Michigan
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Mebbe the powered vent idea would require some control sophistication to turn it on at right times (sorry), but a passive gable vent could also be opened/shuttered from the floor with the right hookup. (Farmtek or somebody?) If your building is pretty air tight you'd need some inlet too, say up a ways on the sunny side and shielded from weather surprises. Dutch445 says the ceiling fan works, and IMO that's a big +1. It's an option, but venting the building somehow is a must most anywhere you live, no? .....
Condensation above your insulation can be scary. Having it at the flat ceiling vs between upper rafters allows easier venting/inspecting. I've seen insulation so close to the roof deck on a new house that lack of circulation led to condensation and black mold galore on the rafters within two yrs. The entire deck had to be stripped off (sawed out between joists) everything treated with some spray (iffy IMO) stuff and several I-joists replaced. 2x4s were added on top with gaps to vent laterally and increase what little airspace there was between the f'glass and an entirely new deck. btw: this house had a seamless rubber roof the was fully intact and in-floor heat on the main floor and in the basement slab.
We discussed powerventing up-slope from channels added along the eaves, but ....... we feared that moist outside air might condense under the deck as before. I haven't seen the house in 2ys since the fix. I'd be afraid to and wouldn't bet that another 1 1/2" or was enough space either, but I hope so. I'd have had lower ceilings, say 9' or 10', more roof pitch, and a lot more room to ventilate or circulate above the insulation.
Sorry, wraiths if I misunderstood exactly where/how your insulation is installed, but the long story came from fearing a repeat of what I'd seen.....
Condensation above your insulation can be scary. Having it at the flat ceiling vs between upper rafters allows easier venting/inspecting. I've seen insulation so close to the roof deck on a new house that lack of circulation led to condensation and black mold galore on the rafters within two yrs. The entire deck had to be stripped off (sawed out between joists) everything treated with some spray (iffy IMO) stuff and several I-joists replaced. 2x4s were added on top with gaps to vent laterally and increase what little airspace there was between the f'glass and an entirely new deck. btw: this house had a seamless rubber roof the was fully intact and in-floor heat on the main floor and in the basement slab.
We discussed powerventing up-slope from channels added along the eaves, but ....... we feared that moist outside air might condense under the deck as before. I haven't seen the house in 2ys since the fix. I'd be afraid to and wouldn't bet that another 1 1/2" or was enough space either, but I hope so. I'd have had lower ceilings, say 9' or 10', more roof pitch, and a lot more room to ventilate or circulate above the insulation.
Sorry, wraiths if I misunderstood exactly where/how your insulation is installed, but the long story came from fearing a repeat of what I'd seen.....
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I agree with zebra5- you must have some type of vent for air movement- the inside must breath a little. I have a small12 by 22 metal building that originally had no vents. I did have sweat on the inside of the roof that dripped. After a winter and one summer I started to notice a scum feeling on everything I handled in the building (mildew buildup?). I installed a vent on each end (9 inches by 12 inches) down low and also the same thing up at the top of the gable ends for some air movement. Never had another problem
quicksandfarmer
Elite Member
You have to figure out how the moisture is getting in. It could be rain coming in through the roof, side or floor. It could be groundwater coming through the floor. It could be coming out of the building as the lumber dries (pressure treated holds a lot of water). It could be from the sweat and breath of the inhabitants. It could be warm humid air that comes in during the day and gets trapped.
Once moisture gets in a building it doesn't get out, you get your own water cycle where during the day the building heats in the sun and the water evaporates and rises, in the evening it cools against the roof and rains inside. It's very destructive.
If the water is coming in as rainwater or groundwater, you need to keep it out. You need to exclude this as a possibility before trying anything else. Moisture can come through a concrete slab that is not visibly wet. A standard test is to put a sheet of plastic over your concrete floor and see if water condenses between the plastic and the floor. If it does, you have an infiltration problem.
If there isn't an infiltration problem, the water is in the air. There's two ways to get rid of it: replace it with drier air through ventilation or remove the moisture directly with a dehumidifier. If the space isn't heated ventilation is cheaper, you should be able to do it for free.
Ventilation doesn't always work: if the outside dew point is higher than the inside dew point, ventilation just makes it worse. That is often the case here in the summer, my preference in the summer is to have buildings either wide open or sealed shut with a dehumidifier.
Once moisture gets in a building it doesn't get out, you get your own water cycle where during the day the building heats in the sun and the water evaporates and rises, in the evening it cools against the roof and rains inside. It's very destructive.
If the water is coming in as rainwater or groundwater, you need to keep it out. You need to exclude this as a possibility before trying anything else. Moisture can come through a concrete slab that is not visibly wet. A standard test is to put a sheet of plastic over your concrete floor and see if water condenses between the plastic and the floor. If it does, you have an infiltration problem.
If there isn't an infiltration problem, the water is in the air. There's two ways to get rid of it: replace it with drier air through ventilation or remove the moisture directly with a dehumidifier. If the space isn't heated ventilation is cheaper, you should be able to do it for free.
Ventilation doesn't always work: if the outside dew point is higher than the inside dew point, ventilation just makes it worse. That is often the case here in the summer, my preference in the summer is to have buildings either wide open or sealed shut with a dehumidifier.
dave1949
Super Star Member
I think you need to consider it as two separate issues that are divided by the ceiling/rafter insulation.
1) Ventilating the air space above the rafters. A gable fan at each end might do fine for that. The type without shutters and a thermostat will run when hot, and allow air flow end-to-end even when not running. These should also reduce the heat load in summer.
2) Controlling the humidity below the rafters.
I agree with quicksandfarmer's comment:
Once moisture gets in a building it doesn't get out, you get your own water cycle where during the day the building heats in the sun and the water evaporates and rises, in the evening it cools against the roof and rains inside. It's very destructive.
Most of the time, some air exchange will be your friend because it removes the build-up of accumulating moisture. This is exactly what occurs in my house if I don't get enough air through it in winter. No ceiling rain
, but plenty of window condensation at night.
There are fairly inexpensive wall-mounted ventilation/exhaust fans that will move a lot of air out, given some has a place to come in. With no windows, you will have to open it up somewhere across the building from the exhaust fan. You could use exhaust fan vents of the type with flaps that the air pushes open, pulls open in your case. You could use a backdraft damper that the negative air pressure of the exhaust fan will pull open, they shut with gravity.
1) Ventilating the air space above the rafters. A gable fan at each end might do fine for that. The type without shutters and a thermostat will run when hot, and allow air flow end-to-end even when not running. These should also reduce the heat load in summer.
2) Controlling the humidity below the rafters.
I agree with quicksandfarmer's comment:
Once moisture gets in a building it doesn't get out, you get your own water cycle where during the day the building heats in the sun and the water evaporates and rises, in the evening it cools against the roof and rains inside. It's very destructive.
Most of the time, some air exchange will be your friend because it removes the build-up of accumulating moisture. This is exactly what occurs in my house if I don't get enough air through it in winter. No ceiling rain
, but plenty of window condensation at night.There are fairly inexpensive wall-mounted ventilation/exhaust fans that will move a lot of air out, given some has a place to come in. With no windows, you will have to open it up somewhere across the building from the exhaust fan. You could use exhaust fan vents of the type with flaps that the air pushes open, pulls open in your case. You could use a backdraft damper that the negative air pressure of the exhaust fan will pull open, they shut with gravity.
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