Need advise on humidity problem inside garage

[GT350Mike]

We bought our house three years that had a 3-car detached carport that I recently enclosed into a 36x36 garage. The problem that I've had since day one is that the humidity level inside is always high, which is rusting my tools and even my golf clubs. The walls and garage doors are insulated but there is not an attic vent or soffit vents. I'm pretty sure my main problem is due to the guy who build the carport didn't lay a vapor barrier between the ground and the concrete.

I'm not really clear on what my options are at this point but I have a few ideas that I'd like everyone's opinion on. I "think" I need to use a de-humidifier, install (at a minimum) turbine fans on the roof, and a few soffit vents. Will this help reduce the humidity??? Any other ideas?

 

[Stinger]

What are you using for heat? Unvented heater?

 

[GT350Mike]

No heat in the garage, yet. I've used a kerosene heater about once or twice in the past year but the humidity problem is year-round.

 

[e-tek]

Has nothing (or v. little) to do with any vapour barrier under the concrete, nor does moisture IN the room have to do with moisture ABOVE the room. You need air movement plain and simple. Install a fan somewhere to **** air out. Does NOT have to be very powerful - not an "Exhaust" fan. Are there windows? Go open one a crack RIGHT NOW. Then, put a small window fan - or otherwise - in it ASAP.
I like to use "duct fans" - normally used to move more air in a long duct - and install them in a hole cut into the wall. Nice vent outside and wala - done. If you mount a fan - bathroom, duct, otherwise - in the ceiling, you'll need to duct it through the attic above and out the roof. DON'T let it terminate in the attic. One good add is a reo-stat - which turns the fan on at a set humidity level, say 50%. The garage (any room) should be 40-50% RH. But I normally leave mine on 24/7 and especially when I bring a hot and/or wet car in.

As for the seperate issue of the attic space, vent it too. Whirly fan, end vents and'or soffit vents - all are good.

 

[GT350Mike]

Thanks for the feedback.....I should have time to get started on this project this weekend. At a minimum I'll be ablet to install a "whirly" fan and soffits. Thanks again!

 

[kbs2244]

I am glad you know about "whirly" fans, or turbine fans.

Too many people don't.

They are cheap, require no power, and move a lot of low speed air.

And that is what you need in AL.

 

[pcmeiners]

"Has nothing (or v. little) to do with any vapour barrier under the concrete"
Is that so ? 1300 sq feet, a possible 2-5 pounds of water vapor a day per 1000 sq feet is nothing ?...Throw 3/4 of gallon of water on a shop floor every day, aside from the normal humidity, sure it will help cause rust.

http://www.kenbondy.com/images/ProfessionalArticles/VETTalkCGEA.pdf

reo-stat? rheostats= A rheostat is an electrical component that has an adjustable resistance. ,a humidistat is a humidity sensitive switch

 

[StingRay]

A lot depends on climate and your particular building. I'm guessing in Alabama that it's reasonably warm most of the year and that your humidity is fairly high. If your garage cools off and the moist air is trapped as the temp goes down the humidity goes up until it hits the dew point and you essentially have precipatation. You could provide better direct ventilation, an air to air heat exchanger or a dehumidifier. With an insulated and vapor barriered building the moisture has to go somewhere and the vapor barrier is like a zip lock bag. Open the bag ( literally) and a lot of problems go away.

Today we are building our garages like living spaces and expecting to get away with treating them like garages. If we drive in wet cars, wash cars, bring in cars with snow on them or crank the temps down so that trapped air can hit the dew point we are not treating them like the living spaces they are built like. The solutions to your problems are no different than they are for typical residential construction. My house has an air to air heat exchanger for this very reason. In my garage I have a dehumidifier for when we bring vehicles inside in the winter otherwise my nice tight garage is like a green house.

A lack of vapor barrier under the slab may contribute a bit but they have been putting concrete down for a long time with no VB under it. Provide air exchange or condition the air. Ventilating the attic is a good idea but it's not going to reduce moisture in the envelope as the attic should be outside the envelope.

If you feel the floor is the problem then just paint the floor. instant vapor barrier.

 

[KenBaker]

The Garage on the front of my house is also a converted closed-in Carport. I also had a lot of problem with moisture covering everything in the garage. I used concrete epoxy, paying a lot of attention to the cracks and transitions to the walls. I have absolutely no moisture at all now. When it would rain, everything in the garage would be wet, especially coming up through the concrete. You may want to try this in conjunction with some of these other things as it worked well for me.

 

[e-tek]

"Has nothing (or v. little) to do with any vapour barrier under the concrete"
Is that so ? 1300 sq feet, a possible 2-5 pounds of water vapor a day per 1000 sq feet is nothing ?...Throw 3/4 of gallon of water on a shop floor every day, aside from the normal humidity, sure it will help cause rust.

http://www.kenbondy.com/images/ProfessionalArticles/VETTalkCGEA.pdf

reo-stat? rheostats= A rheostat is an electrical component that has an adjustable resistance. ,a humidistat is a humidity sensitive switch

Thanks for the correction on "humidistat" - nothing gets by you! But - as for the slab - people have poured concrete on dirt for MANY years and many places stay perfectly dry - mine does. I'm not saying it doesn't have an effect, especially in this case, but I've never seen any shops with concrete floors on dirt have humidity problems. Humidity in a room (shop/gargae/house) is much more due to other factors - humid weather and air, wet cars, cooking, showers, temp changes. REGARDLESS, I think you'd agree, there's nothing he can do about the concrete now....it's all about getting the moist air out and keeping the air moving across the room (garage or attic).

Edit - he could seal the concrete as above - that's also a great idea!!

 

[pcmeiners]

Your right, if you are lucky to live in a dryer region of the country, moisture and condensation are much less of a concern.
Agree, sealing the concrete with at least paint, or a sealer, would cut down part of the moisture issue. As others mention, with an unheated garage, humidid conditions, it can hit the dew point often, which really aggravates the situation.. when I was a Building Engineer (NYC), once in a while (primarily in the fall), the building blowers would remain on over night, due to a computer control malfunction or unintended over ride. I would come in in the morning and there would be gallons of water ( approx 8-10 gallons) in the first floor hall from condensation within the ducts as the dew point would be hit around 3-4 am.

 

[DirtyWhiteBoy]

my new detached garage is insulated to the point that it stays cooler in the garage than outside. when I open the doors on a hot humid day the floor instantly begins to sweat. fans help, but next summer I hope to have a hvac system installed to dehumidify the place. I have a dehumidifier from Sam's Club in the basement garage that does a good job with the same issue. Good luck with the moisture eradication!

 

[GT350Mike]

Its going to ran like crazy this weekend so I'll have to wait before I can install the whirly's.....Please keep the suggestions coming!

 

[Daniel Dudley]

Google up Radonseal. I used this product on my garage floor, and then used a penetrating paint called Top Secret to seal my floor. I think the problem with using a dehumidifier is that the more water you pull out of the air, the more water you pull out of the concrete.

I believe that Radonseal saved my garage.

 

[Daniel Dudley]

www.radonseal.com

No affiliation.

 

[MrWrencher823]

Sorry to revive an old thread, but thanks to all the users on here who helped answer this! I have been having lots of issues in my garage. I'm going to install a small window fan and somehow find a way to lock the window and fan down.
Thanks guys!

Sent from my HTC6535LVW using Tapatalk