Mold in garage/workshop

[s219]

We moved to a new house next to a coastal river here in tidewater VA, and I finally have the workshop of my dreams -- one bay of a 3-bay garage that is walled off and insulated, with a heat-pump + air conditioner wall unit (called a PTAC unit) for climate control. I generally only fire up the PTAC unit when I am out there working on a project for a length of time, so maybe 1-2 times a week. Otherwise, it stays relatively cool in there because of the insulation, shade from tree cover, the cool concrete floor, and influence of the main house air conditioner on the floors above.

Well, today I went out to work on a project, and noticed small spots of mold everywhere, mostly within 2 feet of floor level. On some walls, on some tools, on lumber, cardboard, etc. I cleaned up what I could, and plan to buy a humidifier tomorrow and spray some mold inhibitor down everywhere. In the meantime, I am letting the PTAC unit run full time (set to 80F) to help dehumidify the workshop, and I left the windows open on the garage bays to ventilate. I moved the cars outside, lest they get attacked by mold.

I double-checked all plumbing for leaks and saw none. I know the garage floor has a thick piece of plastic below the slab which is blocking moisture from the ground. Everything is fairly tight and I didn't find any moisture coming into the garage walls or floor. Based on some reading, it seems like the issue is humidity from the coastal air that gets trapped in the workshop and garage when we open the doors to drive a car in/out or do yard work, and later condenses in the evenings when it cools off. It's been an abnormally rainy and humid summer, which surely isn't helping.

In retrospect, I have been seeing clues for weeks and didn't realize it. I had a pair of sweaty gloves that didn't dry overnight. Another pair of washed gloves got moldy and had to be thrown out. The closet doors in the garage swelled and stick. And a whole bunch of my raw iron tools like pry-bars, hammers, cold chisels, etc have gotten rusty.

Anybody dealt with something like this before and have advice to offer??

thanks,
219

 

[user.69169]

Well all I can tell you is after dealing with the mold left behind after bunch of people decided to abandon flooded houses, best thing you can do is get to ventilating.
Good thing is that it really don't take a whole lot of ventilating at least in your present situation. The bad thing is you need to ventilate probably 6 months of the year because what you got there is a moisture creation system. You're headed along the right road when you say it's humidity coming in during the day and condensing at night.

If you have a peak vent up top you can real easily put a 5" computer fan up there in the vent and run a duct down to the garage floor to pull most of the moisture out, remember you also gotta have makeup air to replace what you pull out, or you go noplace fast.

Far as growing mold you see is concerned, you got a whole lot more you don't see, and if the walls are them big wafer chip board bet you got mold working in there too. That stuff is like a greenhouse for mold.

Get all the goodies out of the garage, get yourself a plastic garden sprayer, and some pool chlorine. Mix up the chlorine in water strong as you can get it, andsprey down everyplace inside the garage. Let it work a couple hours and then ventilate the place till you can't smell the chlorine. After that you can put the toys back in the garage. Regular laundry bleach ain't strong enough to kill mold.

 

[Vern]

I had mold in my attic and used this Concrobium 1 Gal. Mold Control Fogger, rented from Home Depot and bought a gallon of the chemical. No more mold.

 

[newbury]

If it's thick wear a respirator mask until you get it under control. Some mold spores can be deadly.
Once you've got mold it's almost impossible to TOTALLY get rid of.

 

[sam5570]

souds like you need ceiling fans to move the air around. this won't get rid of what you already have but will help greatly in keeping new from forming.

 

[s219]

My understanding working in the building industry for a while is that mold spores are already everywhere and more spores are always floating around. The first step is to eliminate the conditions in which the spores grow -- moisture, darkness, stagnant air, etc. Then clean up the mold and spores best you can.

I was planning on getting some Concrobium and spraying it around, but if they have a fogger that would be easier for sure, and give me more peace of mind.

So (removed), I was thinking of some sort of ventilation as an alternative to a humidifier. I could leave windows cracked to pull in fresh air on one side of the garage (they are awning style windows, so we can crank them open a little to open the bottom and not worry about rain). How much is enough flow rate to handle a 3-bay garage? It's about 40 feet wide by 23 feet deep, with 12 ft ceilings.

I realize ventilation will just pull in more humid air, so I guess that approach is just keeping it from stagnating, correct?

Any ideas how effective ventilation would be compared to a dehumidifier? I'm looking at a 70 pint per day unit to handle the same space, probably set to maintain 55% RH or so. Would pipe it to the outdoors to drain. Fairly expensive at $270 compared to a small vent fan.

 

[s219]

Got a humidifier and plumbed up a temporary drain hose to outside. At 2pm when I fired it up, it was reading 90% humidity in the garage, so I have no doubt we were getting to 100% at night when it cooled down -- I'm lucky it wasn't raining in there. Humidity has slowly dropped to 65% at 9:30pm, after 7.5 hours of running. I have it set to maintain 55%, but will see how feasible that is once we get down to that range (60-65% is probably fine -- I read that mold is curtailed below 68%, but you need some extra margin to account for error in the humidistats).

I also picked up some ceiling fans and am in the process of installing them -- need to run a conduit for power and tie into the garage door opener outlets on the ceiling, and get some longer down rods.

Between the humidifier and the fans, I hope that keeps the humidity at bay and helps dry out any moisture remaining in building materials and the slab.

My Home Depot does rent the fogger for Concrobium, and I plan to get it one day this week and run it while I can keep everyone out of the area. Looks like a great solution to bomb a roomful of mold without having to tear the place apart.

 

[newbury]

Got a humidifier and plumbed up a temporary drain hose to outside.

Glad to read you got a DEhumidifier. I've one house in Fulton, Mississippi we only use for storage. We tried keeping it just heated and cooled (between 60 degrees and 82) but it got so humid in there we had to put a dehumidifier in. Made the difference between a sauna and a decent storage place. WELL worth the $$ outlay.

 

[user.69169]

Tell you what, you listen to the radio you hear ads for this wondermachine called THE WAVE they claim is better than anything including the refrigerated dehumidifiers you see all along the curb cause people ain't smart enough to clean the cat hair out of. They even got a website Wave Home Solutions | Basement Dehumidifiers | Basement Ventilation.

Oh I tell you this here machine of theirs will dang sure make you WAVE byeby to your bank account, and if you run it about 1100 years will save you energy dollars enough to pay for it.

Thing is, if you go to their website and look at the Super Machine you can figure out it's an electric switch, and a small fan unit along with some duct work. It ain't nothing a man with about a dollar worth of talent can't make for himself for less than 50 bucks.

I got a fellow I know has been running 3 of the dehumidifiers in his cellar for 4 years, and his wife was madder than a wet hen over the electric bill cause every one of them is like running an ice box in the kitchen when it comes to electric. We got hold of a small blower that came from a high efficiency furnace headed tothe scrapyard, the one that makes the smoke leave the house and put that in his cellar with some 4" pipe going out through the wall. The blower is hanging down so it's just above the cellar floor, cause that's where the air is wettest.
Turned all them dehumidifiers off and just ran that blower 24 hours a day and watched the cellar humidity drop on this little 5 dollar meter from eBay. That blower uses 1/10 horsepower which is a whole lot less than the dehumidifier uses and does 3 or 4 times the work.

Far as how much incoming air you need, as many cubic feet a minute as you're blowing out! You can easy move that through a drier vent on the other side of the room. Chances are you already got enough air leaking into the garage anyhow, but if you don't open a window an inch or so.

When we was dewatering them flooded houses we had fans my nephew makes up from the condenser fan he gets from AC units headed to the scrapper and mounts inside a barrel that's been cut down. You put one of them in a window with some plywood to hold it there, and have it suck air out the house, and open the windows on other side the house and let her go to working. Tell you what, if you ain't got enough windows open you don't want to be trying to open a door with one of them fans sucking. You move air through a room it picks up moisture and hauls it out.

 

[s219]

I talked to the HVAC tech in my building at work this morning, and he said unless we have a liquid moisture source causing problems (leak, slab, foundation, etc), ventilation would be of marginal help in this situation, since we'd be pulling in outdoor air that's starting at 80-90% relative humidity this time of year. He said the outside humidity would have to be a good bit lower than the inside humidity for ventilation to be a primary solution in this case. I can see the reasoning there, though I'd love to run through some thermodynamic equations to get hard numbers before ruling out ventilation.

He thought that once the humidifier dried out the air, the ceiling fans would be enough to keep air moving and the humidifier wouldn't have to run very much until we opened a door and cycled more humid air in to the space. I'm not thrilled about having to run fans or dehumidifiers, but I'd rather the bulk of the running be fans if possible.

I think about the garage at our old house and the barn at our old house that never had mold problems, but they were uninsulated and not very tight, so there weren't issues with the interior cooling down at night (they always stayed hotter than outdoors in the evenings). On top of that, the doors were open a lot more often, as that was the only way the spaces were tolerable. Part of me thinks the old way was better, but it was also too hot to work comfortably in those spaces most of the time. Maybe there is no perfect solution....