Condensation in metal building

[62stepside]

Had the small kerosene heater on last night for about an hour, turned it off walked inside and then just walked out there today and found this.. a bunch of water drops on my metal roof.

I'm not sure what to do here because I don't want it to happen again, I have fixed all the water leaks coming inside, but this is confusing to me. Could it be that I don't have vents on the sides? Shop is 10ft high walls.

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[BukitCase]

Any combustible fuel heater puts out about as much water as it does heat - propane is roughly 1 gallon of water per gallon of fuel burned. Once that water is in your air, anything cooler than the dew point condenses the airborne water. Your un-insulated metal roof will be the coolest place once the heat dissipates, so all that airborne water will end up condensed on the cold metal.

One thing that may help SOME - leave a fan on in the area so the air stays circulating.

The only thing that FULLY helps is insulation, and NOT using a burnable fuel heater, or if you must then spend more for a unit with a heat exchanger - these draw in combustion air from outside, vent the exhaust BACK outside, and have a fan blowing thru the heat exchanger for the inside warmth. That eliminates adding water to the INSIDE air.

Even then, it doesn't hurt to have a separate, ALWAYS ON, circulating fan... Steve

 

[Captain Spaulding]

You likely don’t have or want vents. You’d never be able to heat the building, and you’d be more likely to get condensation from natural temperature swings.

The only thing you can do to really prevent it is to get a vented heater or go to electric heat.

 

[ericm]

Or insulate the inside.

 

[62stepside]

Thanks for the help! Would foam insulation be the easiest for my kind of building?

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[karoc]

Giving a general area such as state sure would help, but either way lot people here love the spray foam and talk about how much of a difference it makes. But there are few that say that it will cause metal to rust, which that has yet been reported here on GJ. Where I live which is TX its not heating that's a battle but the dang heat and humidity.

 

[tsubahog]

I had a similar problem - heated and insulated pole barn with concrete slab. My solution was two setups as shown in the picture, one at either end of the barn. On top of the box is an Aprilaire dehumidifier (not cheap to run so only on when required) which drains to the outside. Inside the box is a radon fan, mounted horizontally and vented to the outside - these run about 9 months a year . I am in NJ so turn them off in the winter to avoid sucking in cold air. I installed this lot about 12 years ago and never had condensation since.

 

[62stepside]

Thank you, I'm in Northern part of South Carolina, South of Charlotte, NC.

I've seen the 220v electric heaters at northern tool that you can hang up that I've thought about getting, but it might be a waste since its not insulated.

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[brownbagg]

its not the metal building , its the heater exhaust, which is h20. propane and lp will do the same

 

[62stepside]

its not the metal building , its the heater exhaust, which is h20. propane and lp will do the same

Ok, was just about to ask about a propane heater, that answers that, lol. I thought about this, https://m.northerntool.com/shop/too...-CMBxWXeyFRrPlu4RDQaAlWyEALw_wcB&gclsrc=aw.ds

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[Showkey]

The metal building can play a part........especially if the insulation not there or marginal.

Warm moist air against a metal roof can cause condensation. Metal buildings are well known for have their own little indoor climate issues.

 

[BukitCase]

As I mentioned in my previous post, you CAN use propane, or ANY burnable fuel - as long as the heater has a heat EXCHANGER built in (as in, combustion air IN and exhaust OUT are BOTH plumbed to OUTSIDE air -

copy this into google for examples

vented propane heater for garage

My shop isn't metal any more, but like yours it isn't insulated (yet) - it started life as a 36x48 pole barn, then added a concrete slab and framed between poles, built trusses in place to eliminate interior poles. Re-framed roof and replaced metal with plywood/3 tab shingles.

Things I do to "survive"

1. Any small power tools live in a smaller, insulated and electric heated "tool room"

2. Stationary power tools each get clamp lamps and 100 watt bulbs under rust-prone metal parts; this keeps those surfaces ABOVE DEW POINT, so no condensation

3. Small/medium stuff I don't want dusty OR rusty go in a re-purposed upright freezer with a single "speed controlled" 100 watt bulb where the DRAIN used to be, and a small covered hole in the top - on that one, the bulb is connected thru a cheap HF "drill speed control" turned down to about HALF - before I did that, bulbs used to die every month or two - AFTER the speed control, they last several YEARS. Bulb gets turned off in warm weather.

4. The larger power tools get "tented" when not in use; I've found these

https://www.amazon.com/gp/product/B00002262L/?tag=atomicindus08-20

work well; have built-in magnets and don't seem to cause problems of their own - they come in several sizes, I have the largest one for the cabinet saw and a couple smaller ones for jointers, etc.

5. I have a couple electric heaters (one's 240 volt) that are ONLY on when I'm working in the shop; they're only to keep ME warm when I'm in there, otherwise my un-insulated shop would cost me an extra $300 a month for 8 months out of the year

So far these things work for me; I occasionally find a small rust spot, likely where I missed with the Johnson's paste wax (non-silicone, used on ALL cast iron surfaces)

I also keep one of these

https://www.harborfreight.com/30-inch-pedestal-shop-fan-47755.html

running constantly on lowest setting, aimed up and DIAGONALLY in the shop area - cheap to run, keeps air moving (less condensation even where I DON'T have light bulbs)

It's a constant battle in unheated, uninsulated areas; high local humidity just ADDS to the problem. Humidity in my area tends to run 40-50% here in summer, 60-75% in winter (constant rain) - so far, the combination of "bandaids" I listed seems to be working for me; hopefully they'll help you.

Now, if you're like a lot of people, go back and RE-READ all those steps - each one made a difference for me. Any other questions, feel free to ask... Steve

 

[Hobby_Man22]

The metal building can play a part........especially if the insulation not there or marginal.

Warm moist air against a metal roof can cause condensation. Metal buildings are well known for have their own little indoor climate issues.

It's the temperature difference. My building has a heat pump, so the moisture in the air thing is bs. You have warm air touching the cold roof. Mine starts raining in all the areas where I have a crack in the insulation. My insulation bats were all about an inch short, so I get condensation dripping from the steel purlins. Been trying to decide what to do about it. Will probably do a test and see what happens if I cut some 2" thick strips to fill the gaps. The issue doesn't occur until the morning time, when the frost thaws when the sun comes up. Funny thing is it's never even freezing out. It will be like 36-38 degrees outside and there will be white frost on the roofs and grass.

 

[housewolf]

It's the temperature difference. My building has a heat pump, so the moisture in the air thing is bs. You have warm air touching the cold roof. Mine starts raining in all the areas where I have a crack in the insulation. My insulation bats were all about an inch short, so I get condensation dripping from the steel purlins. Been trying to decide what to do about it. Will probably do a test and see what happens if I cut some 2" thick strips to fill the gaps. The issue doesn't occur until the morning time, when the frost thaws when the sun comes up. Funny thing is it's never even freezing out. It will be like 36-38 degrees outside and there will be white frost on the roofs and grass.

It’s not BS, it’s physics. Condensation is directly related to the dew point. By adding moisture to the air you are raising the dew point. Anything with temps below the dew point will condensate.

The solution is to control the dew point of the air inside the building (dehumidify) or control the temp (keep it above the dew point). The problem here is, cold air on one side of a thin piece of metal with warm damp air on the other side. It would likely have to be very warm inside the building to heat the metal enough to keep it above the dew point. That’s one reason we insulate when we attempt to control air indoors.

 

[Hobby_Man22]

My heat pump gets it down to about 35 percent humidity inside . Probably 80 or 90 percent outside. What I'm saying is the warm 75 degree air gets into the insulation because it was done poorly and that's when I get water dripping. Almost every batt that has a space showing is one that has water dripping. I used Rockwool, so it just rolls off instead of soaking up like a sponge.

 

[housewolf]

My heat pump gets it down to about 35 percent humidity inside . Probably 80 or 90 percent outside. What I'm saying is the warm 75 degree air gets into the insulation because it was done poorly and that's when I get water dripping. Almost every batt that has a space showing is one that has water dripping. I used Rockwool, so it just rolls off instead of soaking up like a sponge.

Understood. My post above is a simple explanation of how/why condensation occurs. In reality, solving condensation issues can get pretty involved, particularly in a partially finished or shop/garage type building. Usually a residence is sealed/insulated better, has more effective HVAC system, and smaller/fewer doors which likely spend more closed.

My ~750 sq ft metal building shop is foam insulated and has a mini split. A few days after I installed the mini split, on a warm & humid spring day, I thought I’d be hot **** and get the air temp down in the mid 60s. I guess the dew point was low 70s. I opened the bay door and moved a car to the other side of my property and by the time I returned it looked like someone had come in and sprayed everything down with a water hose.

I’ve since learned to pay attention to the weather and keep the set point at least a few degrees above the dew point or if that isn’t comfortable, leave the damn doors shut. It’s the same principle in winter except the heat is usually being pulled from outside of the building. Bottom line is, you let a surface get below dew point, it will condensate. You add humidity, you raise the dew point. We add humidity to about any space we occupy just by breathing but cooking, baths/showers, clothes washing etc… are especially good at it.

 

[Hobby_Man22]

Understood. My post above is a simple explanation of how/why condensation occurs. In reality, solving condensation issues can get pretty involved, particularly in a partially finished or shop/garage type building. Usually a residence is sealed/insulated better, has more effective HVAC system, and smaller/fewer doors which likely spend more closed.

My ~750 sq ft metal building shop is foam insulated and has a mini split. A few days after I installed the mini split, on a warm & humid spring day, I thought I’d be hot **** and get the air temp down in the mid 60s. I guess the dew point was low 70s. I opened the bay door and moved a car to the other side of my property and by the time I returned it looked like someone had come in and sprayed everything down with a water hose.

I’ve since learned to pay attention to the weather and keep the set point at least a few degrees above the dew point or if that isn’t comfortable, leave the damn doors shut. It’s the same principle in winter except the heat is usually being pulled from outside of the building. Bottom line is, you let a surface get below dew point, it will condensate. You add humidity, you raise the dew point. We add humidity to about any space we occupy just by breathing but cooking, baths/showers, clothes washing etc… are especially good at it.

Mine has never done that. It only does it between 7-9am when the temp is below 45 outside

 

[racecougar]

Mine has never done that. It only does it between 7-9am when the temp is below 45 outside

Yes, when your metal is below the dewpoint of the air inside the building due to the cool outdoor temp.

 

[Monza Harry]

Yes, when your metal is below the dewpoint of the air inside the building due to the cool outdoor temp.

Also that steel roof is as cool as it is going to be at that time of the day! Steel is slower changing than the air, once the sun touches that roof it will rise in temp quickly. That is the mitigating factor. Cut or spray some foam into those uninsulated spaces that will keep the moist air away from the cold steel, and solve your indoor rain issues. Harry

 

[cos]

hello anyone were to buy a differential thermostat that doesn't cost 300 dollars. I quit looking. They cure above problems.

 

[Hobby_Man22]

hello anyone were to buy a differential thermostat that doesn't cost 300 dollars. I quit looking. They cure above problems.

By keeping things above the dew point temp?

 

[cos]

By keeping things above the dew point temp?

Yes 4 or 5 degrees above outside temps. no matter what outside temp are in cold weather.

 

[Hobby_Man22]

Yes 4 or 5 degrees above outside temps. no matter what outside temp are in cold weather.

The shop is always 4-5 degrees warmer atleast. It's probably beause each perlin has no insulation inside it because my batts are short.