Shop tech questions (humidity and mice)

jeepinmatt

jeepinmatt

Old, fat, and grumpy.
Moderator
Joined
Mar 24, 2005
Location
Stanley, NC
I need to keep the humidity and mice out of my shop. Looking for some pro tips.

Shop details for humidity:
34x40x13.5' pole
4/12 pitch steel trusses
4" thick concrete floor with gravel base
Standard 29 gauge steel walls, uninsulated
Standard 29 gauge steel roof with 6" fiberglass insulation and Thermoply panels covering the insulation
Ridge vent (open on both ends, but I'm sure the foam from the panel to the vent is poorly installed so probably plenty of sub-vents)
40ish pint dehumidifier in one corner with outside drain

Shop details for mice:
Never any food or drink stored in building (not even in trash can)
Brush seal in channel at bottom of sliding door
1" gap at one end when door is closed (obvious thing I need to fix)
All other doors and panels are well sealed
The end of one eave is open, but 13.5ft off the ground, so I don't think they are coming in there. They were basically a non-issue for the first 3-4 years, now I seem to find a new nest every couple of months. They really like my Lista cabinets.
 
braxton357 said:
Hey dumbass you have an AC in your shop, use it.
Click to expand...
There's a leak in the lines, and no ducting, and I'm too cheap to pay the power bill, and the walls aren't insulated, so I'm not sure how effective it would be. No anyone who knows HVAC stuff that could help me fix the leak and run some duck-ting?
 
cranbiz said:
Black snake or a cat will take care of the mice.

Humidity, no help.
Click to expand...
What's that old saying about a picture?
1617289930221.png

1617289959720.png
 
jeepinmatt said:
What's that old saying about a picture?
View attachment 342278
View attachment 342279
Click to expand...

Haha nice of you to put the fan on him to keep cool, doing all that work.


You don't need ducting. I'll come fix the lines and charge it then you got to pay the power bill.
I keep my shop 75 all summer and highest bill is like $120. Well worth it just to keep shit from instantly rusting. Dehumidifier going to run the bill just as high.
 
CasterTroy said:
No insulation will cause sweating if you throw cooling at the problem
Click to expand...
That's what I was thinking. Usually it is pretty dry, but some days the floor is flat out wet even when it is dry outside. And other days when it is raining and humid outside, the floor is bone dry.
 
CasterTroy said:
No insulation will cause sweating if you throw cooling at the problem

I'd tell the deadbeat upstairs to stop eating crackers in bed :huggy:
Click to expand...

It will cause sweating on the outside and possibly on the ductwork... Assuming the building is fairly well sealed and there is any sort of vapor barrier under the slab, ac will keep condensate out of the building.
 
braxton357 said:
It will cause sweating on the outside and possibly on the ductwork... Assuming the building is fairly well sealed and there is any sort of vapor barrier under the slab, ac will keep condensate out of the building.
Click to expand...

This. Metal siding is a vapor barrier, and vapor drive from under the slab isn't a significant source of moisture in this case. I'd be more concerned with any penetration that's letting in outside air. A 1" hole in the wall will let in more moisture than is migrating up through the slab.

Condensation is strictly a function of wet bulb temperature. If your slab (or anything else) is colder than the wet bulb temperature, water will condense on it.

A dehumidifier is basically just an A/C unit that has all the component parts (hot and cold sides) located within the conditioned space. In that regard, it is both a dehumidifier and a small space heater (all heat generated is rejected into occupied space). You'll probably get better performance out of a proper A/C unit. It will be more efficient (SEER) and it will move more air.
 
how about another dehumidifier? I had a cheap one a few years ago in a garage I ran it on a timer came on every 6 hours for 3 hours and then shut off. would have to empty the tank every week or so. helped keep surface rust off my tools and projects. I think I paid like 80 bucks for the humidifier and like 20 on a timer
 
Last edited:
I've had mice get in my upper garage. Fully bricked, with concrete floor. Tight fitting steel 14' door. Only place they Could get in is at the door seal in the bottom corners. Light want pinterate it, but a mouse can slip through. :mad:
 
If you want to get a sense of how much humidity is coming from the slab, get a sheet of clear plastic and tape it to the floor, tightly all round the edges. Wait a week and see how much moisture you see under it.
 
RatLabGuy said:
If you want to get a sense of how much humidity is coming from the slab, get a sheet of clear plastic and tape it to the floor, tightly all round the edges. Wait a week and see how much moisture you see under it.
Click to expand...

Doesn't matter. Depending on how his ridge vent is configured, there could be orders of magnitude more water coming in from there.
 
jeepinmatt said:
I need to keep the humidity and mice out of my shop. Looking for some pro tips.

Shop details for humidity:
34x40x13.5' pole
4/12 pitch steel trusses
4" thick concrete floor with gravel base
Standard 29 gauge steel walls, uninsulated
Standard 29 gauge steel roof with 6" fiberglass insulation and Thermoply panels covering the insulation
Ridge vent (open on both ends, but I'm sure the foam from the panel to the vent is poorly installed so probably plenty of sub-vents)
40ish pint dehumidifier in one corner with outside drain

Shop details for mice:
Never any food or drink stored in building (not even in trash can)
Brush seal in channel at bottom of sliding door
1" gap at one end when door is closed (obvious thing I need to fix)
All other doors and panels are well sealed
The end of one eave is open, but 13.5ft off the ground, so I don't think they are coming in there. They were basically a non-issue for the first 3-4 years, now I seem to find a new nest every couple of months. They really like my Lista cabinets.
Click to expand...
If your shop is reasonably well air sealed, that 40 pint is 1/3 or 1/4 the size needed for that volume of air.

Fwiw on the smaller side of our shop (40x32) it gets condensation bad on the slab and everything multiple times a year. Has a lot to do with the thermal mass of the slab when it cools off at night, and doesn’t warm much during the day, yet the daytime temps and humidity is up. Most of the time spring/fall. Summer it’s too hot so it’s above the dew point, and winter it’s too dry to drop below the dew point.
On the days where it’s bad, I run 2 90 pint dehumidifiers for 4-6 hrs to dry everything out. Or I cut on the 3.5 ton a/c and it’s dry in 45 mins-1.5 hrs. Also sometimes run both to get it dry super quick without chilling everything.
Often on a Thursday/Friday night when I know I’ll be there all weekend and the weather looks like it’ll be an issue, I run one 90 pint overnight and it’s dry when I get there the next morning.
If your shop were 3’ tall, the 40 pint would probably work. If it’s air sealed well, it may maintain it if it runs constant, but won’t keep up with high moisture loads and open doors/windows etc.

A 70pint unit (5-6A) will maintain it better if you just let it run 24/7 but set the controls to keep it at/below 55% RH. More air leaks = more necessary capacity. Faster drying times = more capacity.
Even if you use AC to dehumidify the space, you may need to cycle the heat and ac on the days/times of the year when thermal load is low but humidity load is high.
It’s definitely cheaper energy wise to run the Dehu for me to keep it dry, but mine aren’t permanently installed so they are on rollers for work use and get in the way. It’s definitely faster to use AC to dry it, but I know I’m paying for convenience and speed haha. And yes, I know, I do moisture control professionally and should just permanently install a dedicated Dehu on that side of the shop, I know I know. Got buggies to build....

reminds me I also need to mount the $400 hepa air scrubber in there above my grinding area too.
 
Mac5005 said:
If your shop is reasonably well air sealed, that 40 pint is 1/3 or 1/4 the size needed for that volume of air.
Click to expand...
Its not. I think that is step 1.
Mac5005 said:
Ridge vent, and the gaps around the roll up doors
Click to expand...
The ridge vent might actually be somewhat sealed because the Thermoply covers the ceiling completely from side to side and end to end. However, the gap at the door is about 1"by 12ft tall, because I never got around to finishing that part :lol:

@Ron I actually designed and built the door, and it works really well. It is 1.5x3" rectangular tubing frame with ball bearing rollers and a brush seal. The brush seal rides in a 1-1/4" wide groove at the bottom with ball bearing rubber wheels that prevent it from swaying side to side. I weighs about 400lbs and is designed to stop a 5000lb forklift from driving through. No one has ever built a door this well before. @Ron
 
Back
Top