Indoor rain...

[harryball]

I thought I'd share this. I'm in my new shop and as work progresses the shop continues to evolve as I build the walls, insulate etc... anyway, as we came out of this winter and being in mid Georgia it's not uncommon to have a day with a high of 35 followed by a high of 70 the next day. I hate it when that happens.

Well, at this time my shop has insulated walls and a ceiling that is currently not insulated. It was very cold in the shop, all the concrete, steel etc... is at that 40 degree mark and this warm 70 degree moist air moves in. I've had to deal with humidity before but never like this. Turns out, the temp in the shop was below the dew point of the air. So when this warm air mass moved in it didn't just condensate inside, it pretty much RAINED inside. Everything was WET, puddle WET. Wood, workbenches, shopbot, table saw... I used up a can of T9 and box of rags.

I couldn't for the life of me figure out why the condensation was so bad... then I realized something. UNDER the workbench was fairly dry, UNDER the bot was also fairly dry... in fact UNDER anything was what I would consider normal light condensation. But everything in the open was sopping wet like a bucket of water had been poured on it. After a lot of reading and corresponding with a guy who is more of a weather expert, I finally understood what happened.

With the ceiling not being insulated and the vents in the metal building roof along with the gaps in the roll up doors I haven't stripped yet the warm air outside was able to enter fairly rapidly into the cool space that was below the dew point of the air. Additionally, when I rolled up one of the doors and the warm air poured in it didn't help. The water in the warm moist air condensed and dropped to the floor or whatever it could settle on. The shop was basically a HUGE dehumidifier that dried out the air all over my equipment.

So, I'll be finding a way to mitigate that I guess.

[Brady Watson]

You need some type of ventilation going. It will allow the inside & outside air to be the same. Something like this from NorthernTool (http://www.northerntool.com/shop/tools/product_200434066_200434066) might work for you. There are cheaper alternatives too.

I have a leanto connected to my shop that I haven't closed in yet. The shop was dry, but it was raining yesterday like you mention under the leanto. It's open on 3-sides. The steel roof was condensing water & there were drips running all the way down the purlins. I'm thinking about having it spray-foamed when I close it in eventually.

-B

[dmidkiff]

I think insulation is supposed to stop this indoor rain. If it is as bad as it sounds, then it may take more. The people that I purchased my metal from also sold the insulation. I used a bubble wrap with foil on both sides. It's about 1/4" thick. They said it would stop the sweating. We will see. I also wanted to spray foam my building, but the guys at my supplier told me that the metal manufacturer would not warranty the metal if the spray foam touched the metal. Your mileage may vary. The foam company told me the foam would not stick to the foil. Manufacturer of my metal is Whirlwind.

[Brady Watson]

Hey Dave - I did TekFoil in my shop. It works really well. Not really an insulation as much as a thermal barrier. Keeps heat in or out.

I'm not sure if it sweats above the ceiling or not, it is only insulated @ the ceiling and walls. I never hear any 'pitter-pat' of droplets. I have soffits and a ventilation fan in the ceiling to push the air out of the shop in the semi-warm months or if humidity makes the shop muggy in the Winter - which is pretty rare. You only get condensation when there is a temperature differential, so ventilation has worked well for me. I'll probably do the automatic setup at some point to keep air moving all the time unless I am in there.

My buildings are 10 years old already...so I'm thinking that warranty is out the window anyway. The foam sure is nice for sound abatement. If you insulate anything for sound abatement - hit the ceiling. It makes the biggest impact on quieting things down. I don't have to worry in the country, but when I was in suburbia it was necessary. R30 did the trick for me then.

-B

[harryball]

The core issue was - Shop cold at about 40 degrees, it had normalized to the outside temps over a few days then a sudden warm (70+ degrees F) moist warm front moved in.

The ceiling is not insulated yet while the walls were and the thermal barrier is in place (AtticFoil) which prevented radiant heating from warming the inside of the shop with sunshine. Along with missing weather stripping around the doors, this allowed the warm moist air to enter the shop fairly quickly. When the warm moist air encountered the chilled shop that was below the dew point of the air, water just didn't condense, it dropped from the air like a heavy foggy mist compounding the condensation problem.

The key is... finish my shop. When I finish the insulation and weather stripping the warm air won't be able to enter so readily. I'll also pay attention and heat the shop up to at least 50 degrees when I know a weather event like this is going to happen. There is not much else that can be done but that should take care of it until I can get some HVAC installed, then I should have complete control like my last shop.

I just figured I would share this experience so anyone in a similar environment can learn from my mistakes.

/RB

[donek]

Our wet grinding operations in finishing spew a lot of moisture into the air. On cold nights, that moisture will condense on the fiberglass skylights and then rain down when the heat comes back on in the morning. We've covered most of them with polyethylene film and a air gap between them. This fixes the issue, but we still need to cover about half. We got the ones over benches and machines and never went back to do the rest.