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Need Some Help Dealing with Condensation?

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Forum topic by juniorjock posted 01-27-2012 10:37 PM 945 views 0 times favorited 17 replies Add to Favorites Watch
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juniorjock

1930 posts in 2513 days


01-27-2012 10:37 PM

Topic tags/keywords: metal building insulation moisture condensation

This is one of those post that I didn’t know for sure what forum to place it. My shop is a small (12×16) metal building. I bought the building a few years ago and last year decided insulate it and install a heater. Yesterday I had to take a strip of insulation down to gain access to a 2×4 on the ceiling. I found exactly what I didn’t want to… a small amount of moisture and mold. There’s no damage done—yet. I thought the paper backing on the insulation would be enough, but evidently it wasn’t. Any suggestions? All I can think to do is do some checking and see what I can find. Probably seal it up a little better with tape and caulk where I can. Could I put plastic up on the inside (and tape up any seams)? Would a thicker plastic be okay or should I use a house wrap…. or am I just screwed. Thanks in advance.


17 replies so far

View michelletwo's profile

michelletwo

2290 posts in 1764 days


#1 posted 01-27-2012 10:48 PM

metal buildings will always sweat as temps & humidity levels change. Just the nature of the beast. You either need to keep it totally cold or totally heated. UGH!

-- We call the destruction of replaceable human made items vandalism, while the destruction of irreplaceable natural resources is called development.

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a1Jim

112883 posts in 2325 days


#2 posted 01-27-2012 10:56 PM

JJ
If your insulation has backing and it’s face towards the inside of the building you don’t normally put a vapor barrier on top of that. If your insulation does not have backing on it then a plastic vapor barrier is needed. If your shop is open to the insulated rafters the only other thing I can think of is to run a dehumidifier in your shop. If you have a ceiling and the metal
roof is above that then you need some venting to let the moisture out and you nead to insulate the ceiling and not the roof.

-- http://artisticwoodstudio.com Custom furniture

View Grandpa's profile

Grandpa

3204 posts in 1423 days


#3 posted 01-27-2012 11:04 PM

What Jim said. Also a dehumidifier doesn’t cost too much compared to all the tools and materials you store there. Another thing is they operate pretty inexpensively.

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DrDirt

2597 posts in 2490 days


#4 posted 01-27-2012 11:09 PM

Also how are you heating?
The propane heaters generate a lot of moisture in that relatively small area.
Certainly what some have done for moisture in basements and such is to use the spay on expanding foam type insulation, as it is air/water tight.

-- "If we did all the things we are capable of doing, we would literally astonish ourselves." Edison

View jerkylips's profile

jerkylips

233 posts in 1318 days


#5 posted 01-27-2012 11:09 PM

There are a ton of variables involved when it comes to vapor drive & moisture in walls. Below is a link to a forum I found before we built our house. Post the question for, or search posts by Dana1. AMAZING resource when it comes to this kind of thing..

Green Building Talk

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doordude

1085 posts in 1731 days


#6 posted 01-27-2012 11:15 PM

you need air ventilation. venting the gable ends or soffits

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juniorjock

1930 posts in 2513 days


#7 posted 01-27-2012 11:16 PM

Thanks guys. I didn’t think this was going to be an easy one. The insulation has the paper backing and it is facing the inside. There are two loft areas 4’x12’ above the main floor. The lofts are not sealed off from the rest of the rafters. The center of the shop has no ceiling. It goes up to the top of the building. There is insulation on the roof. There is a 14”x14” screened vent on both gables (I thought that would be enough for ventilation, but maybe not.

There has been a dehumidifier running 24/7 since I bought the building.

Grandpa has a good point about the tools. The good thing is that I’ve never seen any condensation on the outside or inside of any of my machines or tools.

I was thinking the plastic might serve as way to block the heat from getting next the metal on the roof. The roof is the only place I’ve seen the moisture (so far) going to have to take another look.

I’m using a medium-sized electric heater. It does a great job, but makes my meter spin at about 1,000 MPH.

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juniorjock

1930 posts in 2513 days


#8 posted 01-27-2012 11:39 PM

jerkylips is right about all the variables. I’ll try to narrow it down a little.
metal building, insulated with R13.
electric heat (one of those square ones you hang on the wall or ceiling, and cost a fortune to run.)
dehumidifier running all the time.
there is no insulation under the floor (as of now)
building is pretty well ventilated.

It’s my understanding that humidity wouldn’t be a factor with the condensation. The moisture forms when the cold air (outside) meets warm air (inside). I may be wrong on that, I’m certainly not a master carpenter.

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jerkylips

233 posts in 1318 days


#9 posted 01-27-2012 11:56 PM

Definitely look at the site I mentioned above, but I wanted to add a couple points (was trying to multi-task & posted before I finished my thoughts..)

I’m assuming that you have a metal skinned building with wood framing? Type of insulation is as important as anything. Spray foam is a barrier that does not allow any air movement/convection between inside & outside walls. There is no ‘space’ for water to condense. Fiberglass batts are not a vapor barrier – air still moves in the wall cavity & moisture can condense. It’s not necessarily a bad thing as long as the walls are designed correctly. What you DON”T want is to have a vapor barrier on both sides. In that case, any water inside the walls gets trapped inside the walls. Metal outer walls & plastic vapor barrier on the inside wall will cause this. You’ll hear terms like, “dries to the inside” or “dries to the outside” – basically that means, “if there is water inside the walls, where is it allowed to go?” With a true vapor barrier on the outer wall, anything more than drywall & coat of latex paint in the inside can allow moisture to get trapped & cause mold issues.

View Bill White's profile

Bill White

3582 posts in 2708 days


#10 posted 01-27-2012 11:57 PM

Have ya got any fans (ceiling)? They will keep some air movin’.
Bill

-- bill@magraphics.us

View a1Jim's profile

a1Jim

112883 posts in 2325 days


#11 posted 01-28-2012 12:06 AM

If I understand this right you have gable vents in a heated space ? If this is the case your bring moisture in through vents. Gable vents along with soffit vents are meant to keep air flow in non heated spaces so that a attic remains close to the same temperateness as the roof so not to creative condensation problems or ice dams in colder climates and in these cases the ceiling is insulated to keep the home/shop warm.

-- http://artisticwoodstudio.com Custom furniture

View Don W's profile

Don W

15541 posts in 1315 days


#12 posted 01-28-2012 12:09 AM

the paper on the insulation IS a vapor barrier. The vapor barrier goes toward the heated room. You said, The moisture forms when the cold air (outside) meets warm air (inside), this is backwards. Its when warm air (inside) meets the cold air (outside). To fix it make sure you have good ventilation in the attic area. The idea is when you put up insulation you overlap the “paper” to create a continuous barrier. (that’s why unfaced insulation with a poly vapor barrier is better).

You may want to get a vent for the roof with a fan in it to help. They have the vents that work without any power ot put gable end vents in.

-- Master hand plane hoarder. - http://timetestedtools.com

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buffalosean

174 posts in 2135 days


#13 posted 01-28-2012 12:26 AM

I’d go with spray foam if your going to re-do it. Its expensive, but i think it might be a better product if your having condensation problems.

-- There are many ways to skin a cat...... but, the butter knife is not recommended

View juniorjock's profile

juniorjock

1930 posts in 2513 days


#14 posted 01-28-2012 12:47 AM

I knew I could count on you guys. I’ve gotten a lot of good suggestions. Going to think it over and decide what to do. Just about every thread offered something good. Like I said, so far, I’ve only found moister in one place. I’ve taken 3-4 strips down now and they were okay. I wish I could afford the foam, but it took a while to get the dough for the fiberglass. One thing I didn’t mention, and just thought of….. I’ve always had trouble with wasps in the shop. After I put up the insulation, I hardly ever saw one. When I took the insulation down yesterday, there were maybe 100 or more dead bees between the insulation and the metal roof. That tells me that there is probably air moving that I was not aware of. It doesn’t take but a small crack for the wasps (and lady bugs) to get in. But that could be enough to cause problems. Going to have to check that out too.

Thanks again.

View Don W's profile

Don W

15541 posts in 1315 days


#15 posted 01-28-2012 12:52 AM

If you have fiberglass insulation touching the metal roof your going to have problems. You have to have some air movement between the insulation and the roof. That’s why buildings have ventilated soffits.

-- Master hand plane hoarder. - http://timetestedtools.com

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