Excessive Moisture on Windows and Doors

[shunting]

I have a problem with excessive moisture on some of my windows and doors in my garage since I insulated it. Here are some stats..

poured foundation, sealed with perimeter drain
vapor barrier under concrete slab
22' x 40' x 8 1/2'
2" x 6" walls
Sill Seal
Vinyl siding over house wrap over 7/16" OSB
R19 Owens Corning pink with vapor barrier in the walls
R29 blown cellulous insulation (9 1/2") in the attic, no vapor barrier (per mfg recommendation)
Well ventilated attic
7/16 OSB interior sheeting, all seams and corners caluked, painted with latex paint

Prior to insulating and finishing the garage I had NO moisture problems at all for 2 years. The moisture seems to gather on the insulated overhead garage door and the stationary Pella windows. The crank out casement Pella windows do not have moisture. There is a huge temperature difference between the outside and inside even when the garage is not heated. The other day it was 4* outside and 48* inside without heating it and it rarely goes below 50*. This seams great, but the moisture is excessive. I am really worried that I am going to rot out the (expensive) aluminum clad Pella wood windows and the framing under them, because the windows and overhead door are literally dripping. I am hoping this is because of all the new wood, insulation, and paint I have put on. Maybe things need time to "dry out"???? If this problem persists next winter I am really gonna get worried. Any ideas would be appreciated. Thanks, Shawn

 

[anojones]

Warmer air holds more moisture as vapor than colder air. When that warm air hits the cold surfaces of the door and window you get condensation. It wasn't a problem before insulation because the garage was cold inside, now it's warm. It sounds like you either need more ventilation or a dehumidifier.

 

[shunting]

Thanks for the reply. I have tried a dehumidifier, but it doesn't pull much moisture out of the air at all. I have run a box fan out there to circulate the air and that seems to help. I was just hoping that running a fan all winter would not be a long-term solution.

 

[Franz©]

Keeping the air circulating will minimize condensation.
Household dehumidifiers haven't got a hope in hell of handling most garage situations.

You can cycle exhaust the humid air inside the garage a few times and probably improve things, or you can just mop the windows down.
If the situation is ongoing it might be time to think about building a dehumidifier that acts in concert with Mother Nature and doesn't consume many endangered electrons causing you to have to buy Carbon Credits.

 

[Vicegrip]

What are you using for heat? An unvented gas heater will dump lots of water into the air.

 

[CraigFL]

The real problem here is that the dewpoint temperature, the temp where water condenses, is the same or lower than the inside surfaces. The only remedy is to heat the garage so that the surfaces are above the dewpoint temperature(so the water doesn't condense) or to remove as much water as possible. As noted, dehumidfiers do not work well in cooler spaces. If your dehumidifier is removing any water at all, you might find it more effective to locate it in the warmest spot in the garage-- near the ceiling next to the house. And as mentioned, unvented combustion type heaters pour water into the heated space and therefore should be vented.

 

[shunting]

Thanks for the feedback guys. To answer a couple of questions....

The dehumidifier does seem to draw more moisture out of the air when the garage is heated.

The moisture situation is happening both when it is heated and when it is not. I believe it is slightly worse when it is heated.

I am using a 80000 BTU portable propane fired convection construction heater. It basically looks like a metal bucket turned upside down with slots cut in the side.

 

[CraigFL]

...I am using a 80000 BTU portable propane fired convection construction heater. It basically looks like a metal bucket turned upside down with slots cut in the side.

What this heater does is convert oxygen and propane to water and heat. It is the source of your water problem because the combustion products and the heat are being discharged into the garage.

 

[shunting]

I agree that the heater does add moisture and contributes to the problem, but it happens even when I am not heating the garage. I suppose moisture could be trapped in the garage from when the heater was on. Is there something I can use that would provide a dryer heat? Something that won't break the bank? I don't need much, even though the garage is 880 square feet, it stays pretty warm without using a heater.

 

[Franz©]

Unless you go to a heater that exhausts the product of combustion outside of the garage, youmight as well hang a lawn sprinkler in the garage and save the cost of propane.

Thise heaters are real nice, I own a couple, but they produce huge amounts of water vapor when they burn gas.

 

[CraigFL]

Unfortunately, this is one of the problems with cheap heat. You really need a gas heater that isolates the combustion from the heat circulation -- called a furnace. It uses outside air for combustion and just heats the indoor air adding no moisture. You could also use electric heat from strip heaters or resistance heat like those small towers you buy in the store that glow red and have fans.

Even if you do all this, you will probably still have some condensation that will need to be removed by your dehumidifier. You should use it when the room is warm so it's most efficient at removing the moisture.

 

[Vicegrip]

Thanks for the feedback guys. To answer a couple of questions....


I am using a 80000 BTU portable propane fired convection construction heater. It basically looks like a metal bucket turned upside down with slots cut in the side.

Bingo. When it is on it is dumping water in your shop. When it is off the water condenses. This water soaks into everything including your OSB walls and waits until the temps drop. Ditch the un-vented heater and the problem will go away.

 

[kbs2244]

Full agreement.
You need venting. Big time.
Either get a vented heater or open a window, and "waste" some heat, to vent what you are useing now. If you leave the window open about 2 inchs for an hour after you are done working it will cool down the garage, but that escaping heat will also **** a lot of moisture out with it.

 

[skinanbones]

how about using a wood stove for heating the garage its a very dry heat and if used continually would dry out all moisture in the garage. If space is a issue look at pellet stoves same kind of heat takes up less room and these could be left on continually so you have a warm shop to use when you want. As far as cost to install just as cheap or cheaper than a gas furnace if you shop around and cost to run is diffenantly allot cheaper than gas. I've got two or three customers that will have the complette system paid for in three year with what they are saving from gas or oil.

 

[Vicegrip]

Where do you live and how often are you in the shop? Use profile can help to make a recommendation on a heat method that might be the least cost over a long time. a big gas fired furnace might be the cheapest to run but might be the most expensive to install. When you are working in the shop how long are you there? If you are in the shop for 8 hours a week 2 hours at a time and live in a warmer climate the ROI will be 50 years compared to some cheap electric baseboard heaters or a couple kerosine heaters.

 

[shunting]

I live in Central Ohio and I am in my garage most evenings for 1-2 hours and on the weekends 2-8 hours. This weekend was a little warmer so I did not run a heater at all. Garage was 55*-60* and there was still a lot of moisture, probably left over from when I was heating it. I was thinking about some electric heaters. I also have some infrared (I think that's what they are called) vent-less propane heaters left over from our home remodel. They are the type that have ceramic looking grids in them that glow. They mount to the wall for a secondary heat source. Would those be OK? I know you guys said that I need to have it vented, but I was wondering if these would be marginally better than what I have now.

 

[Franz©]

For every cubic foot of gas you burn you create X volume of exhaust gas. The exhaust is a combination of water vapor and Co2. It's basic chemistry, and unless your name is AlGore you can't change the laws of Physics & Chemistry.

Presuming the BTU value necessary to heat the garage doesn't drop the infrared units will create the same number of cubic feet of water vapor.

About the best option would be to determine if the infrared unit came in a vented model, and if so retrofit the units you have to vented operation.

 

[SteveU]

I would like to put in the vented IR tube heaters in my shop to both keep everything warm enough to minimize condensation & get away from the fumes of running the kerosene salamander.

 

[Vicegrip]

IMO Get some all electric units and heat as much or as little as you need unless you can hang some vented heaters or go with a heat pump. Little portable heaters are cheap up front. Electric will be low cost to start but more expensive in the long run. How long depends on what better systems are out there and how much you need to pay for over what you can do for yourself. A through wall, split or standard heat pump might be nice as you get heat and cool from one outlay of $.

Another cheap up front method was mentioned. Kerosene heaters don't dump the water like gas does. There are clean non smelling fuels that you can use to get away from the smell if it bothers you. It costs more than kerosene.

Don't burn your shop down with a portable heater! They are a common fire starter.