Condensation in the Southeast?

[USAFpj]

I live fairly close to the NC/SC/GA borders, and wanted to see about your different experiences with condensation in your shops.

My pole barn will have R6 insulation in the ceiling and walls, but no planned AC or heat. (2) 10x10 insulated doors, and (1) insulated steel man door. (3) 2x10 clear panels will be installed under the South facing eave, so that may add or subtract from inside moisture. Concrete slab as well.

What has been your experience with moisture in the SE, and before we start this build, should I be adding ridge vents, fans,...?

 

[matt_i]

I lived 10 years in metro Atlanta, worked a lot of hours in a shop near Toccoa, GA...my experience there and even here is that you get in trouble when its chilly and this raging warm front full of moisture comes up from the gulf. Then everything wants to sweat, rain, etc. I had a ministorage for a short time where it would rain from the underside of the bare metal roof...

So, I kept the shop doors closed as much as possible, and used some sort of box fan to keep air moving. Without A/C, both in my garage shop and the metal building shop, was nearly unworkable during the summer. The metal building shop did get cold during the winter, but never dipped below freezing according to the internal thermometer. My friend who owned the shop had the A/C working but never got around to piping up the natural gas. Usually the sun would come out and warm things up.

In your concrete slab, I would use a vapor barrier, and also use #57 stone (its washed imestone 3/4" nominal) as your sub slab base to break the surface tension with moisture creeping up.

 

[USAFpj]

Matt, what kind of insulation did either of the shops have; and would that have helped?

My Uncle has a red iron shop nearby me, and doesn't seem to have any issues with humidity or comfort. He has slight white mold on vinyl tractor seats, and keeps the doors closed as well. He does have a propane heat set up, but hasn't turned it on in years. Perhaps my pole barn may be a bit more 'drafty' for air movement?

 

[junkman104]

I live in the NC,GA,TN area and my pole building has bubble foil insulation in the walls and ceiling. It doesn't rain inside but condensation does happen when you get a weather change.

 

[MushCreek]

I'm in the upstate as well (Tigerville). The big problem in my barn seems to be the slab. As stated above, a warm humid system after chilly weather makes the floor sweat. If I keep the doors shut, it isn't as bad, but I kind of wished I had put some foam under the slab. Since I don't heat my barn (yet), an insulated slab probably wouldn't help that much, since it would eventually get cold anyway. Anything of significant mass is going to do the same thing, so I'm going to have to keep my lathe and mill oiled up good to prevent rust.

 

[USAFpj]

Hey, MushCreek, what's your insulation situation in your shop? Also- is it just enough moisture that you feel running an AC or Dehumidifier would solve the issue?

 

[Showkey]

Your location does not matter the issue and causes are the same. In the south you need more AC. In the north we need more heat. But the science is the same....DEW point . In the summer I do not AC my shop but run a dehumidifier in the summer. My shop was running 60-75% relative humidity at times which is too high. 50% is my goal. My shop is very well insulated R19 in the walls R60 in the ceiling.

You need more insulation ( less air exchanges) and to solve or manage condensation you condition the air in the shop or the home). The insulation keeps the conditioned air in the shop and unconditioned out.

First thing is measure the temp and humidity over time. Likely a dehumidifier would be the first step in conditioning the air. A better dehumidifier will work to lower temps with out freezing up. With conditioning the air you can only sit and watch the variation in air quality.

 

[MushCreek]

Right now, the barn isn't insulated or heated at all. Plans are to do basic fiberglass in the 2X6 walls, and under the loft floor. I would think it would take a big dehumidifier because of the size of the shop. I'll have to figure out a way to seal up the sliding doors, too if I plan to add HVAC. I've been building our house, so the barn hasn't had much done other than dried in.

Our attached garage is insulated but not heated. There doesn't seem to be as much condensation in there, so maybe insulating the walls and ceiling slow the temperature change enough to limit the problem.

 

[JoeFin]

Showkey is right

Location doesn't matter - it is the temp variations and dew point that cause the moisture to accumulate on the walls, ceiling, tools - what ever you have in the shop space

R-6 simply isn't enough

I have R-13 in the walls and R-36 in the ceiling and it is almost a constant temp 24 hrs a day

 

[USAFpj]

I hear ya on dew point, guys-

Joe, how is it that my Uncle's shop has hardly any indication of condensate? His insulation was the 3in fiberglass that apparently held an R4 rating (early nineties). Nothing special in the slab- 5in of fiber, no rebar or barrier, etc.

The basic R6 barrier is what will be installed from the builder. I imagine that between overhead fans and a dehumidifier, if the level is still not adequate, I'll then investigate more insulation or other avenues...

 

[EdT]

I built a shop about 50 miles north of Atlanta about five years ago. Conventional stick construction with ordinary FG insulation in the walls and roof. I built a couple of swing out barn doors which have not worked out too well AFA sealing the building. I was concerned about sweating since I have a lot of machinery in the shop and I didn't want it to rust. So far, I have not had a problem with sweating. I have a couple of mini splits that I run when I'm in the shop and it's too hot or too cold, but that's not every day. Even in summer when the shop gets nice and cool, sweating has not been an issue. Maybe I'm just lucky.

 

[USAFpj]

Ed, do you have a shingled roof?

 

[JoeFin]

I hear ya on dew point, guys-

Joe, how is it that my Uncle's shop has hardly any indication of condensate? His insulation was the 3in fiberglass that apparently held an R4 rating (early nineties). Nothing special in the slab- 5in of fiber, no rebar or barrier, etc.

I couldn't tell you - but 3" fiberglass is typically R-13 thou

And the density / thickness of the siding and or sheet rock all play a factor in the overall R value. For instance, mine also has 5/8 sheathing outside and 5/8 sheet rock inside.

What I do know - I used to have a condensation problem and now I don't

 

[matt_i]

The building I posted of earlier was a red iron building - clear span with 4" fiberglass wrapped batts. The kind that flop completely over the building and down each wall and are taped at the seams, then pinched between the roof metal and the purlins with screws.

I think if I built a shop in the SE, I would think about a radiant barrier, it seems to make more sense financially, the farther south one goes.

 

[Showkey]

Remember sweating, condensation and rust are the extreme sysmptoms. You can still have high humity conditions causing issues that not as obvious. Mold and mildew in areas not seen are the first and key indicators. Organic materials like leather, rubber, cotton are the first to be effected. Mildew ..........invite the wife in....does this place "smell funky" ????
Black streaks behind the insulation on the wood sheathing ?

Measure temps and humidity so you can make good sound decisions and see if your making positive or negative changes.

 

[USAFpj]

In resurrecting this thread- if you have a fully insulated 30x50 building without vents or HVAC, is it best to close all doors, turn on fans, and de-humidify; or...

Open up all doors, and turn on fans for circulation? I have large doors on opposing ends that allow a nice breeze through.

Today's summer heat here in SC is 90F with 90%RH on humidity. I'm wanting to avoid mildew and be somewhat comfortable working inside...

 

[58Yeoman]

My metal building is 24x40 with maybe 3" styrofoam insulation in the walls, 6" fiberglas in the ceilings. OSB walls and ceiling. Two insulated steel overhead doors. I run a house dehumidifier all the time in the summer when it's hot and humid, and leave the doors closed as much as possible. The other day it was about 8* cooler inside and felt much better w/o the humidity. I have the dehumidifier sitting on one of the work benches, and drains into the sink. I also have 3 ceiling fans running constantly. When the humidity drops, I open the windows at each end and turn on a window fan. This works for me.

 

[Whitworth]

Raleigh location. Summer, mostly hot but low humidity. As stated, winter can be cold days punctuated with warm, moist days, leading to rust. Sometimes so bad I walk into the shop and see tiny rivers of condensation on the cast iron surfaces.

I didn't have any problems when we lived in a new construction, super well insulated attached garage.

Just opening the walk-in door on a damp day in my current shop you can see the effect localized to that area.

There are a couple of large mass pieces of iron in the shop that act as an early warning system. The lathe chuck is one of them. When it starts to sweat it's time to turn on the dehumidifier.

 

[Oregon rock crusher]

Here in the NW I get along nearly all the time being able to open the doors to my well insulated shop and not have issues. The exception occurs when the shop is cool inside and a warm and humid air mass moves in. Until the outside air humidity drops the doors must remain shut....any intrusion of outside air, even around doors will let that moist air inside where it will condense on the cool machines. Insulation helped a lot...especially noticeable after the doors were insulated. Good door seals tightly sealing the shop and keeping moist air out finally stopped the problem. Ed.

 

[DTE]

I am here in NC, my shop is block and I run a dehumidifier 24/7 and the humidity stays around 50-60% . I empty it twice a day. I am not going to have my tools rusting.

 

[pcmeiners]

We have the same issue, but it worse for you. The air stays warm and moist until the early morning hours (about 4 am), then cools considerably/fast, at that point the moisture forms water on cooler surfaces. Best you can do is make sure you have a good/intact vapor barrier under the concrete, as a great deal of moisture travels through concrete. Secondly, as mentioned, you do not want air changes during the night, times of rain or fog.
I would have a dehumidifier in place with a humidistat, if you have good vapor barriers and little air infiltration, the unit should not run constantly; if you have it running between 12-9am, that should cover most of the condensation period, but you also have to figure in times of rain and fog.

Ran a school building in Brooklyn which had blowers for air exchange and for the kitchen. Especially in spring and fall, if the blowers were left on, water would form on the metal in the duct around 5:30am. I am not talking about a little water, approximately 5-10 gallons depending on the humidity during the night, which ended up in the first floor hallway. As soon as a timer was installed to kill the blowers from 12am to 8:00am, the issue went away.

 

[USAFpj]

DTE, are you keeping tolerable temps in there with the doors closed and humidifier going? You got fans going?

58Yeoman- I finally think I understand. Don't watch the temperature, but watch the humidity level. If it's 95 degrees with 50%RH, feel free to open doors and windows and enjoy the breeze. If 95 degrees with 90%RH, keep her sealed up, as that 'breeze' won't be comfortable...

 

[DTE]

DTE, are you keeping tolerable temps in there with the doors closed and humidifier going? You got fans going?

58Yeoman- I finally think I understand. Don't watch the temperature, but watch the humidity level. If it's 95 degrees with 50%RH, feel free to open doors and windows and enjoy the breeze. If 95 degrees with 90%RH, keep her sealed up, as that 'breeze' won't be comfortable...

You know how it is living in the south it is hot. I have about 2/3s of my ceiling insulated with R30 and nothing in the walls ( 8 in. block ) I do have 10 ft ceilings and that helps keeping the heat up higher but I also have a 24in. variable speed fan installed in the at the top of a end wall. When I am out there during the day I open the bay doors about 3 feet to keep the sun out and run the exhaust fan. It works for me, but I have worked in the heat my whole life. I still have to install a ceiling also and I know that along with finishing the insulation will help keep the heat out.

 

[MushCreek]

In my barn, the humidity doesn't seem to be enough to rust things. The only time the floor sweats is in relatively cool weather when the slab has gotten good and cold. Then we get warm, humid weather, and the floor sweats. I haven't had any issue yet with mildew, either. Maybe because my barn leaks enough air to keep it relatively fresh. On a day like today (very hot), the barn is tolerable until about noon. When it's this hot, I keep the doors shut until it's just too hot inside.

I think the high ceilings in my barn keep it comfortable and help disperse humidity. Under the loft, the ceiling is 12', and at one end, it goes all the way up- 27'. When ya gonna come by and see the place?

 

[USAFpj]

When ya gonna come by and see the place?

Gotta make it out of Kabul alive, first! And the question is this: when am I going to come by and see my place?! The electrician hooked up all the lights, my Uncle used a generator to power them up, I then left the next morning. The GJ guys have seen more of my shop than me!

Mush, I saw where the RH was only at 43% today; so I can see it feeling a lot cooler than what it was yesterday- 95%RH. That's just nuts...