Advice on ventilation and exhaust fan

[twk63]

My workshop was originally built as a reservoir building. There is only one entrance, the garage door, and no windows or vents. The building is 40 feet by 40 feet, with 25 foot high ceilings (or 40K cubic feet)

https://www.garagejournal.com/forum/showthread.php?t=454133&showall=1

When the garage door is closed, the air stagnates inside the building and I end up with a stale and mildew smell. I have a 4 foot shop fan that I use to try to circulate the air but with only one exit, it isn't the most effective solution.

The challenge for me is that the walls are 18" thick rebar-reinforced concrete and not easily drilled to create ventilation ducts.

One idea I am thinking of is to install a large roof mounted exhaust fan. There is a manhole opening already cut in the roof that was the original access into the building when it was used as a reservoir. I can run this while I am in the shop with the garage door open to circulate fresh air while the shop is in use. This is the model I am thinking of:

https://www.globalindustrial.com/p/...bdd20gb-a-1-1-2-hp-115-230v-1-ph-5471-cfm-odp

A couple of questions:

Is this exhaust fan overkill or is 5471 CFM appropriate for a 40K cubic foot building? Are there other solutions that would accomplish the same objective easier and cheaper?

 

[Showkey]

Interesting building.

First suspect is the relative humidity is uncontrolled when the building is closed up. Acting some what like grandma’s basement.

My guess the humidity levels are getting upwards of 70-80% .......thats when bad things start happening like mold, mildew, funky smell etc. The mold and mildew will first form on organic materials like leather, rubber, cloth, paper first.

Venting and ventilation might help but that only works if the outside air is better than the inside air. That’s not likely in most climates....especially in summer. Fans will NOT help humidity levels........fans move mix up the humidity And air ........fans do not dry the air plus spread the mold spores etc.

Venting the building with outside air that is damp will not fix the problem in the long run. If the building is cool and damp and the outside air that is warm and damp.........that combo will create a condescending mess in the building will the concrete and metal sweating.

If the humidity is high ( measure it) a large dehumidifier will control the humidity.......the goal would be 50% humidity.

There are multiple other threads on building, shops, basement, metal building with this humidity issues. First step measure the temperature and humidity levels.

 

[Kaizen]

Holy nuclear bunker!!
Think I would spend the money on a concrete saw and cut some windows or such. Could be up high for security.
I’d the manhole cover raised so no water comes in? Guessing when the installed it they didn’t care about that


Sent from my iPhone using Tapatalk

 

[bdbecker]

I agree with Showkey - if the humidity is high, fans are not going to be the solution long term, finding a way to dry the the air would be the best. That being said, being able to evacuate the shop air is something you'll want to be able to do if you're going to be grinding or welding in the space, so installing a fan to pull fresh air into the area could be a good intermediate step to at least help with the smell.

That fan would give you 8.2 air turns an hour, which I don't think be overkill at all. While there isn't anything on this list for "water cistern converted into a Porsche garage", it does give you an idea what is recommended for other activities so you can determine what you think is best.

https://www.engineeringtoolbox.com/air-change-rate-room-d_867.html

 

[Showkey]

My shop today measured:




That’s with a dehumidifier. Prior to conditioning the air I had humidity levels above 75%. The first issue was the welding gloves got moldy. Today bringing outside air in my case would be obviously anti productive.

I do not have AC but the shop never gets above 75* even with temps in the 90*. The building is shaded in the woods setting. Very well insulated. Keep the doors and windowS closed.......I do run an exhaust fan when Welding or painting.

 

[hoyt]

A commercial kitchen exhaust fan is useful for this. They are always available at used kitchen equipment supply houses.

 

[twk63]

The exhaust fan is installed and does a decent job of moving the air while I’m in the shop with the garage door open.

I’m measuring 80-85% humidity in the structure when everything is closed up. My plan is to acquire a good quality industrial dehumidifier that will manage the humidity to a pre-set level. I. E. Run whether I’m there or not. We are drilling a hole through the wall to run the outlet hose.

What are the top manufacturers for commercial dehumidifiers and what would you recommend for a 40k cubic feet structure?

 

[bdbecker]

Not trying to tell you how to spend your money, but have you considered just getting a conventional HVAC system with suspended ducts for your shop? Then you'd have both heat and AC covered.

Quick and dirty math (I'm no pro, so I might be way off)... 40x40 is only 1600 square feet. You've got 25' tall ceilings, so figure you have roughly the same cubic feet of a 4000 square foot house with 10' ceilings. I'd bet a 4 or 5 ton AC unit would probably work pretty well in that space, maybe even smaller since you only have one big room. Just a thought...

 

[nadogail]

Not trying to tell you how to spend your money, but have you considered just getting a conventional HVAC system with suspended ducts for your shop? Then you'd have both heat and AC covered.

Quick and dirty math (I'm no pro, so I might be way off)... 40x40 is only 1600 square feet. You've got 25' tall ceilings, so figure you have roughly the same cubic feet of a 4000 square foot house with 10' ceilings. I'd bet a 4 or 5 ton AC unit would probably work pretty well in that space, maybe even smaller since you only have one big room. Just a thought...

I agree with the above.