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davidhmail 02-09-2007 07:59 AM

Humidity/Condensation Problems
1) Everything in my garage rusts quickly and badly (table saw, tools hardware, etc.). How do I stop the rust? Garage is not heated or cooled, and is not fully sealed. Table saw has been very hard to protect, and I would like to get more woodworking tools if I can stop this problem.

Details: Single car garage with utility room attached at back end, and garage and utility room attached to house on the left side. Utility room and garage share the same single pitch roof. Attic space is about 5' high at peak. We never keep cars in the garage, just tools, bikes, and storage. Neighbors have similar model house with very similar garage layout but their garage is fully drywalled sealed and they don't have the rust problems. Currently there's a 2' x 3' open access panel in the garage ceiling with no door.

I assume the solution is to seal the the ceiling opening and other air gaps, and maybe run a dehumidifier. Will this probably solve the rust problem?

2) Attic space above garage will then only have 2 sources of ventilation: a triangle gable vent and a small capped stationary roof vent. Should I add soffett vents?

3) Garage attic also covers utility room, and there's no insulation above utility room ceiling. I assume I should add appropriate loose fill insulation above utility room.

4) Is it okay to use "great stuff" foam insulation to seal back and sides of electrical boxes?

Square Eye 02-09-2007 08:11 AM

I have the same problem in my shop.
I have a fan that I run sometimes and it seems to help.
Get the air moving and it will help.

cibula11 02-09-2007 11:39 AM

Where do you live?

If you are getting condensation....most likely it is because the lack of ventilation in the area. Do you have gable vents or ridge vent on your roof and venting on your soffit? If the garage and your house share the same attic, make sure you use a vapor barrier, i.e. insulation with this, so that the moisture from your garage doesn't get into the house or start mold growth. If the space is not insulated that could be where you might want to start.

davidhmail 02-09-2007 12:46 PM

After I posted this message, I googled this topic and found several postings in woodworking forums about this. They said the air condenses on the cold metal b/c it's colder than the surrounding air. They recomended waxes, protectants, and plastic bins for tools and hardware. Those posts also suggested the concrete floor may be a source of moisture too.

The rusty conditions seems to exist even when I'm not working the garage much.

I live in Maryland. The utility room and the garage share the same 1st floor attic. Rest of the 2 story house has a separate attic. The garage utility room attic area only has the one gable vent, and one small 6" capped vent in the middle of the roof. No soffitt vents. My heat pump blower unit is in the utility room and the return duct from the 1st floor runs through the garage-utility room attic back to the blower unit in the utility room. I do not heat or air condition the garage.

I'm still unclear what I can do if anything to prevent condensation/rust in garage.

Will sealing the garage space reduce the supply of moist air into the space and reduce the rust problem? Will increasing ventilation thru garage space decrease rust problem?

Soffit vents will improve air flow in the shallow ends of attic, but the garage and garage attic are separated by the drywall (with a large attic access door opening in it). Garage and garage attic only exchange air with eachother thru this opening, and this opening is near the gable vent in the attic space. So there is wide open air flow from garage to the garage attic to the gable vent. To get more air movement in the lower garage space I would have to add some vents in the garage walls.

Even if I can't do anything to stop the rust conditions, I should still probably add some insulation to the uninsulated utility room ceiling. Am I putting the vapor barrior under the insulation, next to the drywall and the studs?

Kerrylib 02-09-2007 01:45 PM

Heating will reduce condensation on equipment. (Lower relative humidity)

More airflow will remove moisture from air. At least to the humidity level of the air that is being brought in (typically outside air)

Insulation isn't going to help you unless you add heat/ac. May make it worse by reducing any natural air movement.

Think about your attic. Insulation prevents heat from getting there, ventillation carries away the moisture that does get there.

Short of conditioning the air, you're options are likely limited.
As suggested in woodworking forums, wax and protect tools, store smaller tools and hardware in plastic bins (even add some dessicant in there w/ them)

Wherever the moisutre is coming from keeping the air moving will help to keep humidity levels as low as possible.

Leftenant 04-13-2009 04:16 PM

Garage Condensation
Venting is the common solution.

In the meantime, covering steel surfaces with oiled rags
prevents further rusting.

Nestor_Kelebay 04-16-2009 12:06 AM

Start searching for sources of humidity getting into your garage from the attic, such as bathroom and kitchen ceiling fans or clothes dryers that just exhaust their humid warm air into your attic. That's a definite no-no where I live.

I'd also buy a cheap fan and run it in the garage to circulate the air in there. The air movement will dry out any condensation that forms, thereby keeping the metal in the garage dry-er.

If you're open to the idea, buy a second frost free fridge and put it in your garage. Run the defrost drain hose through a window (or through the wall) so that the defrost melt water doesn't get re-evaporated into the room air. That way, you can save money by stocking up when foods you like are on sale and dehumidity your garage simultaneously. You live in California so your winter temperatures don't get cold enough that thickening of the oil in the compressor during the winter would create problems.

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