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Old 01-18-2007, 12:08 PM   #1
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Moisture problems when 'heating only when needed' in insulated garage?


Hey guys,

I have an insulated garage and want to heat it with a 240V 4800W forced air heater 'only when I'm in there'. I'm not sure if this is a good idea, as I've heard (myth?) that I will have moisture problems (rusty tools, circ saw blades, etc) if I do this.

Is this true?

I plan on getting a wood stove by next winter and will use that when I'm in there working (maybe the forced air to take the chill off quickly).

Will I have problems?

I've also heard that starting an exhaust fan running after I'm done (and the heat is shut off) will prevent such a thing?

What is the logic/science behind this?

Thanks so much

Tim

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Old 01-18-2007, 02:17 PM   #2
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Moisture problems when 'heating only when needed' in insulated garage?


Assuming your garage is properly insulated, electric heat should not raise the humidity levels in and of itself. Electric heat does not put moisture into the air. There is one source of moisture that CAN increase however...your floor. If you have an unsealed slab, heating the space can raise the amount of water vapor coming up thru the slab. Warm air is thirsty air and the slab will release more vapor into the air to equalize and soon as you leave the garage and things cool down..that moisture condenses out. I sell silicate deep penetrating concrete sealer to folks all the time for this purpose. It is a brain dead easy DIY project and can be painted over in case you decide to get all fancy.

The wood stove, on the other hand, will likely raise humidity levels. Anytime you burn something (wood, propane, diesel, etc.) you release moisture. Also, when you burn, you need air intake as well as exhaust into the structure. If the intake comes from outside and it is wet outside...this raises the moisture levels. A dehumid is probably not a bad idea. Problem with the exhaust fan is that most garages are pretty well sealed from the house so it may draw cool moist air in from outside and the higher vapor levels may condense out quicker.


Last edited by MoldBuster; 01-18-2007 at 02:20 PM.
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Old 01-18-2007, 02:21 PM   #3
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Moisture problems when 'heating only when needed' in insulated garage?


Thanks for the reply. I will defenitely look into the concrete sealer (seems like a good idea for spills/etc anyways).

Won't all the moisture exit the chimney? Intake air will come from inside (through the draft right?) so I shouldn't be producing most air into the garage right?

How expensive are dehumidifiers to run in this situation?

Thanks again for the reply.

Tim
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Old 01-18-2007, 04:44 PM   #4
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Moisture problems when 'heating only when needed' in insulated garage?


Quote:
Originally Posted by timg View Post
Thanks for the reply. I will defenitely look into the concrete sealer (seems like a good idea for spills/etc anyways).

Won't all the moisture exit the chimney? Intake air will come from inside (through the draft right?) so I shouldn't be producing most air into the garage right?

How expensive are dehumidifiers to run in this situation?

Thanks again for the reply.

Tim
I'd say a small dehumidifier and small AC draw about the same power. You could put the dehumidifier on a timer so turn it on when you go in and have it shut itself off when you leave.

With the concrete paints I've seen you may as well paint a layer of ice on the floor. As soon as it gets wet it turns to a scateing rink. Useing somthing with sand or a texture can help.

The moisture from the wood will exit the chimney but the stove sucks air in from the garage so the garage will suck air in from the easiest path be it inside your house or outside the garage.

I wouldn't worry about rusting tools. I've worked in many garages that go hot-cold on a regular basis without rust problems. Then in my basement everything rusts despite dehumidiers going all the time.
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Old 01-18-2007, 04:44 PM   #5
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Moisture problems when 'heating only when needed' in insulated garage?


Nope, moisture doesn't necessarily always leave the chimney. It can come from both the draw into the area and from the unit itself. Most of it does go up the flu...but not all.

And yes, the sealers are a good idea and they work well for spills too. The ones I sell are pretty simple. I've done my garage and I've spilled moldicide and mold coatings (think thin paint) on the concrete many times without any issues.

Dehumids aren't horribly expensive to run. A simple portable unit would do it (just remember to drain the tank!) All you are trying to do is take the edge off. 50% is a good number to shoot for. You may not even need one if the floor stops wicking. Buy one of those inexpensive thermometer/humidity units, put it in there and see what the humidity reads after you do the sealing and put in the stove.
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Old 01-18-2007, 04:49 PM   #6
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Moisture problems when 'heating only when needed' in insulated garage?


Great advice here guys! Really appreciate the expertise.

I'll see if I can find some concrete sealer locally. MoldBuster, can you suggest any brand/type of the stuff?

I'll be sure to get a thermometer/humidity unit to keep an eye on things.

Thanks again, just came across this website and it has been great so far!

Tim
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Old 01-18-2007, 04:56 PM   #7
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Moisture problems when 'heating only when needed' in insulated garage?


The one I like is WET Deepseal 1000. If you can't find it locally PM me and I can probably have it drop shipped to you. Works best if you have an on-grade slab without any major cracks or seepage problems. There are other products I recommend if that isn't the case.
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Old 01-18-2007, 05:03 PM   #8
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Moisture problems when 'heating only when needed' in insulated garage?


I'm actually in Canada, so unless the drop ship cost is 'great' I'll probably have to go local.

Thanks, I'll see what I can find. I can apply this myself with a regular ole garden sprayer?

Tim
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Old 01-18-2007, 05:05 PM   #9
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Moisture problems when 'heating only when needed' in insulated garage?


Where in Canada? If you happen to be in B.C. I'm just south of the border in Bellingham. Can meet at the border (have it in stock).
Yes, a regular garden sprayer works fine.
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Old 01-18-2007, 05:26 PM   #10
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Moisture problems when 'heating only when needed' in insulated garage?


Eastern Canada (Halifax, Nova Scotia).

So how exactly should I refer to this type of product?

Thanks
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Old 01-18-2007, 05:38 PM   #11
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Moisture problems when 'heating only when needed' in insulated garage?


Ah...other side of the continent. You want a silicate sealer. This is NOT the same thing as a garage floor paint or a normal surface concrete sealer. It penetrates down into the concrete structure and forms silica crystals which block water and strenthen the concrete structure. The more water in the slab, the stronger it gets. Kryton is another product to look at and they are Canadian based so you may have an easier go of finding it locally.

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