Pole barn condensation

[JohnBuffaloMN]

Thank you RayfromTX for your explanations of dew point and condensation.

When I bought my property it came with a corrugated steel building on 2x4 framework (about 30x40 foot) "A" frame with the lower 10 feet finished, insulated and sheetrock with heat! I was excited to have a nice shop. A short time later, I noticed the condensation rusting all my tools... arggh. Eventually the entire ceiling started coming down - the (18" of) blown in cellulose insulation saturated with water - no vapor barrier. What a mess. Had to tear down and get rid of a LOT of sheetrock and cellulose. After talking to a few people and witnessing water on the floor and condensation on the bottom of steel workbenches, I did some grading to make sure the foundation wasn't pooling water.

Now I have a nice space covered with steel shell that no longer appears to be a terrarium and am basically in the same situation as the karman 4564 - how to finish the interior to prevent problems. I think this building was built in the 70's by Bubba and Bubba Inc. The concrete work is pitiful. The walls all still have the sheetrock and fiberglass and I think they put polyethylene as a vapor barrier behind the sheetrock. The upper level was not finished, and is shall we call it "well ventilated" but has no fans or vents. I actually don't think the water was originating on the roof in my case.

I'd like to have a heated workshop for wood working and whatever else, but am hesitant to improve this building fearing ending up with similar condensation problems. It would make a good pole barn with some higher clearance doors and maybe I put good money into a new shop. I'll be following along here.

 

[RayfromTX]

Metal buildings are a proven structure for storage. It is when we try to make them into living quarters or introduce other sources of moisture that the problems begin. Some sources of moisture that create issues are soil, combustion appliances such as kerosene or natural gas heaters or animals or pressure washing activities. The most resilient structure for handling intermittent moisture events is an earthen or masonry structure. It can store the moisture that would collect from time to time. Wood structures can store and release a smaller but still substantial amount of moisture. Metal has no capacity to store moisture so it collects liquid water immediately. Metal buildings give you no fudge factor so if you are going to use one then the system for climate control and thermal resistance will need to be more perfect and will be more costly. Refrigerators and freezers are good examples of how it is possible to use metal structures in a thermally resistive system. It is not for the uninformed to try this.

Fiberglass insulation is cheap but that is it's only claim to fame in the insulation world.

There are wall systems that can work in any climate or use. The wall systems that people are more familiar with will work under certain conditions and in certain types of construction. It isn't a mix and match proposition. You need to stay on one side of the picket fence or the other. Having one leg on either side of a picket fence can be dangerous and painful.

For those wanting to study this further, you can learn about the second law of thermodynamics and building science. As with any online study these days you will need to sift through a vast amount of marketing to get to the science and the truth. Avoid anything presented as product based solution when you are trying to learn about this stuff. They are selling you something, not teaching you. Study the second law.

I realize that this isn't something most people are willing to do but this forum does attract those seeking knowledge so perhaps there are some here that will be excited to learn about this. I was fascinated by it but I got lucky. 20 years ago when I started learning about this, the internet was a better learning tool because search engines were not yet marketing tools that limited access to knowledge. The info is still there but it is buried by companies marketing products.

Good luck.

 

[RayfromTX]

Oh and one added note. It is still possible to get to the info online by avoiding websites owned by manufacturers and supply houses. In the future that will become harder to do. As they recognize that we are avoiding the sales pitch they will add layers of pages that hide who they are until you are several pages deep. I see some evidence of this already but in 10 years it will be worse. Study now. If you want reference material I can suggest a couple of books to look for and a couple of websites. The books are better.

 

[mikester]

insulate

 

[Snobdds]

The only true solution if no intent on insulating is building a cold roof. This requires putting OSB on the roof, then putting furring strips on top of the OSB. Then put the metal on the furring strips. This makes a thermal break between the inside and outside surface of the metal. It's really not much more expensive to do it this way.

If it was me, and understanding the new building sciences of roofs and walls, I would insulate the outside of the building only. I would build the frame of the pole barn. Then use the zip panels, which is OBS with a 1" thick layer of dense foam on the outside. Then put on the metal. Do this on the roof too and then just put furring strips on the zip panels then the metal.

Like someone explained to me. If you were trying to keep your rib cage on your body warm, what would you rather have? A parka covering the entire rib cage or strips of insulation between each rib bone? Yea, insulate your place like a coat and you will be much better off...

 

[bkrgi]

Also I will add if your not going to heat a insulated building full time then condensation can quickly build up inside the space especially as temps swing up and down...is the swing up and all the warmer moist air condenses on all the cold stuff inside. At that point you need a big hole in the insulation to let things vent.
It is such a fine line in cold places where temps rise fall rise fall.......