Shop Humidity . . .

[Steven DeMars]

Warm moist days, cool / cold nights.
Leave a couple fans running, resulting in the below:
* Very minor amount of condensate on ceiling. (insulation moisture barrier)
* Very minor amount of condensate on walls.
* Sealed smooth finished slab looks like it has been hosed.


Need help from someone in an climate similar to Louisiana . . .
Have a 20' X 30' Metal Building.
Interior 9'-6" walls & 11' peak
Walls & ceiling all insulated with 8" thick batt.
Insulation on walls is tightly sandwiched between exterior metal and interior metal.
Insulation on ceiling is held against roof interior of roof panels with taunt bands.
(1) 4'X8' roll-up door with typical roll-up air leaks on side and top.
(1) 8'X10' roll-up door with typical roll-up air leaks on side and top.
(1) walk door.


Looking at a large dehumidifier, but not sure if leakage from doors will make it useless.


Any suggestions or experience with this appreciated. . . what are you doing?


Steve

[Charlie Velasquez]

Dehumidifier is a good solution. Some will suggest air conditioning. The problem with A/C is once you start you almost need to keep it going. You are so humid, running the A/C will almost certainly lower the inside temp to below the outside dew point. If you get any air infiltration that air will certainly have a high moisture content.

You can certainly use A/C, but you should either spend some time sealing your a/c area better (good idea no matter what you do) or do something to remove the water vapor from the air that gets in; a dehumidifier. So, a dehumidifier is an important part of the solution no matter what you decide.

[Malcolm Schweizer]

Embrace the rust!

They make a rod that plugs in and gets mildly warm to rid damp in closets. You can put one in the bottom drawer of your (large) tool cabinet. Also you can get rechargeable silica gel packs. You bake them in the oven to recharge them. I have to recharge them weekly.

As as for large dehumidifiers, I gave up in them- too much trouble. I constantly had to drain the reservoir. Also they use a lot if power. I just am meticulous with oiling and protecting tools. All the planes are in plane socks.

[Charles Lent]

If you are using a dehumidifier in a large area the reservoir will certainly fill up quickly. That's why they make the reservoir with a hose connection on it to keep it drained so the dehumidifier can continue to run and you don't have to keep emptying the reservoir. If there is no way to run the hose to a drain I have friends who have mounted their dehumidifiers high enough on a wall so that the hose can be run to a laundry sink. If that can't be done, a condensate pump can be added to the reservoir that will pump the water through a 3/8" plastic line to a drain, or even to the outside of the building.

In a former home my shop was inside the basement and I had a floor drain near the furnace. I ran both the central air conditioner and the dehumidifier drain lines to this floor drain. I cleaned and serviced both every 6 months and it took less than an hour to do both of them. Mostly, the dehumidifier only needed a detergent spray and rinse of the coils and the reservoir. Not much trouble at all to keep my shop and basement rust and mildew free.

My present shop is in a detached building with a window style heat pump. It runs most of the year set at 45 deg in the winter and 75 deg in the summer. I set it for more comfortable temps when I'm working in there, and it keeps my tools rust free. I use Johnson't Paste Wax on the cast iron, but don't do much else to keep the mildew and rust away, and my shop is less than 5' above and 40' away from a 250 acre lake. I keep it closed up, except when opening the doors to get materials and people in and out. It is insulated well, but no vapor barrier other than the covering on the bat insulation.

Charley

[Loren McDaniel]

Steven,
I'm in the same boat. Metal building, insulated walls and ceiling. Almost identical to your situation. When it's moist outside, rust inside. I had just scrubbed and waxed my table saw this past Friday and after a very humid and rainy Sunday my tablesaw was covered in moisture and as you said my painted concrete floor was as if a water hose went off in there. My shop is far from totally sealed but it was the best I could do. I'll be watching this thread if it develops.

I'm in Ethel (just north of Zachary) by the way.

Loren

[Steven DeMars]

I do know that since I started running some box fans I no longer get condensate on ceiling, walls or equipment. I do still get it on the concrete floor. That is the warm moist air coming into contact with the cold concrete. I need to still lower the humidity level, so it looks like I am going to go with a dehumidifier. Will be sealing the roll-up doors with brush seals.Steve

[phil harold]

reduce the air leaks
if you can keep the air from bringing in moisture less will condensate
roll up doors are not insulated I presume
I too my 14'x12' door and framed it in to a 6'x6'8"
also how much moisture is seeping thru the floor
trenching and tililng to remove groundwater from the around the slab will help too
I think an air conditioner will serve you better get a smaller one, it will run longer but remove more moisture
basicaly the same thing as a dehumidifier, and you living in Louisiana I think you will enjoy the the air conditioned space in july

[Jim Foster]

Getting a few cheap digital thermometers that also show humidity is a great start to understanding how big your humidity problem is. Home depot has them for as little as $5.00. Anything over 53% and your in the danger zone. Anything under and rust will not bloom. I've been running a humidifier that has an automatic on/off setting that drains through a hose under the garage door for five years now and have not had a spot of rust in the garage or the loft above where my shop is. It runs a lot in the summer months, but I think it's been worth it. I also have a small window A/C unit to cool the shop a little in the summer, the humidifier tends to heat things up. Also, the humidity in the shop has spiked for brief periods (several hours) up to 75% or more during severe weather, but using the humidifier seems to keep rust in check. The outside humidity is a whole different ball of wax, often 75-100% during the summer months

[Charles Lent]

Jim,

I think you are using the word wrong. A humidifier adds moisture to the air. A de-humidifier removes moisture from the air. I'm not picking. I just don't want anyone buying a humidifier when they really need a de-humidifier to remove moisture from their shop.

Charley

[Charlie Velasquez]

If you are using a dehumidifier in a large area the reservoir will certainly fill up quickly. That's why they make the reservoir with a hose connection on it to keep it drained so the dehumidifier can continue to run and you don't have to keep emptying the reservoir. If there is no way to run the hose to a drain ....

I work part time on HVAC and IAQ for my school district. During the humid summer months, when we shut down our buildings' A/C, humidity is a real problem. We deal with it with dehumidifiers. If we have no place to continuously drain them we put a piece of plywood over a heavy duty 65 gal. WHEELED trash can, set the dehumidifier on that and drain it into the container.

We empty the container about every 3-5 weeks, when it gets about 2/3 full (remember each gallon weighs about 7.5 pounds). If your doors and such are average tight, you will get about 3 gallons that first day, then a little less each day. Undisturbed, with normal air infiltration, it levels out about .5-.75 gal/day. It works well in classrooms of about 7,500 cubic feet. Two of them also worked well in our media center of about 100,000cu.ft., but that is very well sealed.

PS. we glued 1x1 strips around the perimeter of the plywood to form a watertight seal, then drilled a drain hole in the plywood. It:
1. was a backup if something went wrong with a dehumidifier discharge tube
2. kept the dehumidifier from "walking" off the plywood as it vibrated when cycling on and off (dehumidifiers are on wheels)
We learned we should do this the hard way...