I have a roughly 20x20 attached garage. Needs cross ventilation to prevent mildew from building up on the ceiling/walls. Should I punch a couple holes in the nice garage doors to install vents (assuming it would be best to do that at the base), or punch through the walls at the upper wall area to create a vent to the outside? Do the vents need to be on opposite sides or is two on same side (walls) ok?
venting an attached garage - suggestions needed
- Thread starter CT2012
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sands35
Well-known member
Where do you live? (Update your profile for your location please!)
It might be better to install a dehumidifier or AC unit.
It might be better to install a dehumidifier or AC unit.
sands35
Well-known member
A ceiling fan or two then.
Any other sort of ventilation will require holes in the walls anyway. In that case, you might as well put in a dehumidifier.
Any other sort of ventilation will require holes in the walls anyway. In that case, you might as well put in a dehumidifier.
Sorry I meant I'm fine with a hole in wall for a vent but would prefer to not have hole at base for dehumidifier condensate drain if I can avoid it (for aesthetic and practical reasons). House is built on a sloping hill, so at least 1 wall vent, while about 6' from garage floor, is really about 1-2' above the foundation ledge. I can stick a shrub in front of that and it'd be hidden.
sands35
Well-known member
Ah - then put the de-humidifier on a shelf?
You can get condensation pumps for not much.
The basic problem is that unless you cut humidity, there will still be a moisture problem. Fans will help to keep moisture suspended and limit condensation, but it's not the same as removing humidity from the air. That presumes that you have reasonable air leak control.
Do you know where the moisture is coming from? Outside air or infiltration through the floor or below ground wall?
You can get condensation pumps for not much.
The basic problem is that unless you cut humidity, there will still be a moisture problem. Fans will help to keep moisture suspended and limit condensation, but it's not the same as removing humidity from the air. That presumes that you have reasonable air leak control.
Do you know where the moisture is coming from? Outside air or infiltration through the floor or below ground wall?
duh....a humidifier on a shelf! that's actually a great idea. sometimes the simplest solutions work best.
i happen to have a ceiling-mounted outlet to plug a humidifier into (prior owner installed it; it was likely in there for hanging shop lighting).
there is an air handler in an adjacent room (basement) with a pvc condensate drain line that punches through the garage sheetrock and is mounted to the garage wall, traveling outside into gutter downspout drain line. that air handler drain could easily be tapped if I get the humidifier a few inches higher on a shelf to let gravity do its magic.
terrific idea, thanks.
p.s. moisture source is a great question, i'm not exactly sure where it's coming from. not through floor, that's nice & dry. likely a combo of outside air and at the foundation. as soon as things dry up i'm either doing myself or have someone dig a trench and put in french drain outside along the wall that runs the perimeter of the garage foundation wall. that will be a lousy job, i'm not looking forward to the labor (of myself) or the cost if someone else does it. tight cramped space too, since a deck covers a chunk of that length of wall. i have eaves and gutters that keep a good amount of water away from foundation, but again, the house is on a slope so water will find its way wherever it wants to go, eventually.
i happen to have a ceiling-mounted outlet to plug a humidifier into (prior owner installed it; it was likely in there for hanging shop lighting).
there is an air handler in an adjacent room (basement) with a pvc condensate drain line that punches through the garage sheetrock and is mounted to the garage wall, traveling outside into gutter downspout drain line. that air handler drain could easily be tapped if I get the humidifier a few inches higher on a shelf to let gravity do its magic.
terrific idea, thanks.
p.s. moisture source is a great question, i'm not exactly sure where it's coming from. not through floor, that's nice & dry. likely a combo of outside air and at the foundation. as soon as things dry up i'm either doing myself or have someone dig a trench and put in french drain outside along the wall that runs the perimeter of the garage foundation wall. that will be a lousy job, i'm not looking forward to the labor (of myself) or the cost if someone else does it. tight cramped space too, since a deck covers a chunk of that length of wall. i have eaves and gutters that keep a good amount of water away from foundation, but again, the house is on a slope so water will find its way wherever it wants to go, eventually.
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sands35
Well-known member
I don't think it will matter how high you mount it. Just so you can service it if needed and get the gravity drain working properly. It shouldn't block the air vents either. If you put it on a shelf, you will want to either strap it to the wall with bungees or something or put a lip on the shelf so it can't vibrate off.
Frankly I don't know how to size dehumidifiers, but garages have big doors and are probably leaky.
If you don't have any obvious water leaks, it may be an air gap someplace. Think about taking off outlet covers and caulking around the electrical box and sealing off where the wire comes into the electrical box. If the air-leak if big enough, you could even see dirt streaks around the spot.
If you have an attic or crawl space above the garage, the builders might not have dressed the insulation properly around the top plate and rafter joint.
Yeah - keeping water away from the foundation is a good idea too. It will be a PITA, but it will be worth it in 10 years when you don't have a rotten wall because of a "minor" moisture problem.
Frankly I don't know how to size dehumidifiers, but garages have big doors and are probably leaky.
If you don't have any obvious water leaks, it may be an air gap someplace. Think about taking off outlet covers and caulking around the electrical box and sealing off where the wire comes into the electrical box. If the air-leak if big enough, you could even see dirt streaks around the spot.
If you have an attic or crawl space above the garage, the builders might not have dressed the insulation properly around the top plate and rafter joint.
Yeah - keeping water away from the foundation is a good idea too. It will be a PITA, but it will be worth it in 10 years when you don't have a rotten wall because of a "minor" moisture problem.
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BillK
Well-known member
ct,
I think I would put my energy towards finding the source of the moisture. Unless you are right on the water there really is no reason for an attached garage to have a humidity problem. Washington DC area is about as humid as it gets during the summer and I don't have any issues with stuff in my attached garage. Have never seen a bit of rust on anything.
I think I would put my energy towards finding the source of the moisture. Unless you are right on the water there really is no reason for an attached garage to have a humidity problem. Washington DC area is about as humid as it gets during the summer and I don't have any issues with stuff in my attached garage. Have never seen a bit of rust on anything.
bill i'm really stumped on source of h20. my house is built into a sloped hill and the garage has exposed cinderblock walls on both sides. the blocks themselves, however, have no leakage, not one drop of moisture anywhere. it's got drylock on it, but even then, no evidence anywhere in case the drylock was penetrated. i took that as comfort when re-doing my garage (i put r-9 foam board against the block in between the joists).
i did, however, have a leak at a point above the block foundation ledge that must have trickled in over the years (this house is new to us by the way, so the leak happened during prior owner's tenure). maybe it is a clapboard issue (if so, i might find it, because the house is getting painted and a lot of clapboard repair is being done). a small section of drywall in the garage had mold on it (about 10 sq. ft.). i ripped that out and re-did it with green board.
i'm thinking that water trickled in from or along another part of the foundation ledge (again, maybe via clapboard issue) and made it's way to the garage area. that's a needle in haystack, unfortunately, and digging a trench with a drain is my only real potential cure. i've got good roof eaves and gutters to divert water from the foundation itself, which is a good thing. but again, the house is on a slope and there's only so much i can do without doing a massive re-thinking & re-building of areas that might present water penetration (I'd have to rip out a ton of decking and **** several feet down to trench).
i did, however, have a leak at a point above the block foundation ledge that must have trickled in over the years (this house is new to us by the way, so the leak happened during prior owner's tenure). maybe it is a clapboard issue (if so, i might find it, because the house is getting painted and a lot of clapboard repair is being done). a small section of drywall in the garage had mold on it (about 10 sq. ft.). i ripped that out and re-did it with green board.
i'm thinking that water trickled in from or along another part of the foundation ledge (again, maybe via clapboard issue) and made it's way to the garage area. that's a needle in haystack, unfortunately, and digging a trench with a drain is my only real potential cure. i've got good roof eaves and gutters to divert water from the foundation itself, which is a good thing. but again, the house is on a slope and there's only so much i can do without doing a massive re-thinking & re-building of areas that might present water penetration (I'd have to rip out a ton of decking and **** several feet down to trench).
BillK
Well-known member
Backing up a bit ...... why do you think you have a humidity issue ? Things rusting ? Have you actually put a humidistat in there to see what it actually is ?
feels like a sauna, some condensation on ceiling/walls. when we moved in the ceiling had surface mildew on it (wiped right off).
last night i tried sands' recommendation for a fan, and that worked wonders. cracked the garage door just a tad as well.
no moisture coming through concrete floor by the way, that's tight, no issues there.
last night i tried sands' recommendation for a fan, and that worked wonders. cracked the garage door just a tad as well.
no moisture coming through concrete floor by the way, that's tight, no issues there.
sands--of all the basic things, i've had a floor fan going in the garage for the past couple hot & humid days, that's done the trick just fine. simple & effective. dunno how long or continuous i can run a fan, however. it's a bigger one from hampton bay (home depot), identical to this:
BillK
Well-known member
I think you need to find out where the moisture is coming from. That is not normal unless you are right on a lake or the ocean and even then it should not be that bad. I have a cousin that lives on the Cape and he has no problems like that.
My biggest concern is if there is water leaking or something similar that is causing the moisture. If there is, where else is it causing damage ??? You say that the floor is dry ? Why don't you try the test the use for epoxy, take about a 2 ft square piece of clear plastic and tape it to the floor with some duct tape. Let it sit overnight and see how much moisture is under the plastic.
Is there any chance that the previous owner did something stupid like run a dryer vent or bathroom exhaust fan ducts into the attic above the garage ?
bill i'll give the floor/plastic thing a try. thanks for the tip.
no weird venting in the room. above the garage is living room, so there's no attic. def. no water leaking from pipes. we've ripped through a lot of walls during renovation and haven't seen any evidence of pipe leakage anywhere, so that's a plus.
i should clarify my sauna comment--it wasn't that bad, but the lower part of the walls on one side (where the hill is steepest) would get light moisture on it. when we bought the house, the garage ceiling had surface mildew on it, so clearly they had some sort of a problem. now how long it took to get that mildew, i dunno. could have been years, and they never cleaned it off.
again, the fan thing has been night and day in terms of air circulation and dampness/smell. basically nothing to speak of since running the fan.
the rains here have been positively insane lately (northeast), and like i said, the house is built on a hill (wedged into a slope), so there's fill on both sides of the block foundation. i dunno what or how far down any perimeter drainage there is. i've been doing a lot of landscaping lately and finding new pipes here and there (that were previously blocked and/or hidden). based on their positioning, my guess is there's some drainage on both sides.
no weird venting in the room. above the garage is living room, so there's no attic. def. no water leaking from pipes. we've ripped through a lot of walls during renovation and haven't seen any evidence of pipe leakage anywhere, so that's a plus.
i should clarify my sauna comment--it wasn't that bad, but the lower part of the walls on one side (where the hill is steepest) would get light moisture on it. when we bought the house, the garage ceiling had surface mildew on it, so clearly they had some sort of a problem. now how long it took to get that mildew, i dunno. could have been years, and they never cleaned it off.
again, the fan thing has been night and day in terms of air circulation and dampness/smell. basically nothing to speak of since running the fan.
the rains here have been positively insane lately (northeast), and like i said, the house is built on a hill (wedged into a slope), so there's fill on both sides of the block foundation. i dunno what or how far down any perimeter drainage there is. i've been doing a lot of landscaping lately and finding new pipes here and there (that were previously blocked and/or hidden). based on their positioning, my guess is there's some drainage on both sides.
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sands35
Well-known member
The footer drains are normally against the footers - so all the way down at the bottom of the wall. If surface water is expected, then there can be surface french drains as well.
The 1st house I owned had clogged footer drains - and running water through the basement wall. Of course the roof gutter drains where clogged and that didn't help.
The engineering behind condensation is pretty simple. If there is a surface that is below dew point, condensation will form. So if you are getting condensation against a wall that has fill on the other side, I'd bet it is close to 55-60*F, then you either need to lower humidity or raise the temperature of the surface or both. All the fans do is promote evaporation of water that is trying to condense. So it will help with mildew, but your water problem is still there.
If you decide you need to get down to the footer drains, you can rent a mini-excavator for a few hundred a day There is a learning curve, but that is half the fun. You can have the walls excavated in a half a day. I know you mentioned you have a deck there, but that is one idea to get the digging done fast.
I'd check the obvious first with the roof gutters and surface water.
The 1st house I owned had clogged footer drains - and running water through the basement wall. Of course the roof gutter drains where clogged and that didn't help.
The engineering behind condensation is pretty simple. If there is a surface that is below dew point, condensation will form. So if you are getting condensation against a wall that has fill on the other side, I'd bet it is close to 55-60*F, then you either need to lower humidity or raise the temperature of the surface or both. All the fans do is promote evaporation of water that is trying to condense. So it will help with mildew, but your water problem is still there.
If you decide you need to get down to the footer drains, you can rent a mini-excavator for a few hundred a day There is a learning curve, but that is half the fun. You can have the walls excavated in a half a day. I know you mentioned you have a deck there, but that is one idea to get the digging done fast.
I'd check the obvious first with the roof gutters and surface water.
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very good question and i'll make note of that. all gutters are fine and cleared. i'm having some gutter work done in a few weeks and will have a crew run a camera into the main drain line where certain downspouts feed into. i know one side of the house where the downspouts feed into is fine (i just replaced about 60' of 4" drain line to redirect the flow into a certain part of the yard). the other, where the condensation is, might be affected somehow. i don't know there the drain feeds to on that side of the house. i can see the junction underneath the deck, but from there it goes into the ground. maybe the leach field (i'm on a septic system).
sands35
Well-known member
Put a hose down it and see where it goes. If it bubbles up, it's clogged. It might be tied into the road gutter drains (just a guess). You should be able to hear or see the discharge to find it.
Does your house have a sump? Might run there. BTW, probably not good if gutters go into the footer drains.
Does your house have a sump? Might run there. BTW, probably not good if gutters go into the footer drains.
I installed a "Garage Unit Air Extractor Dehumidifier" in my detached garage. Keeps the humidity down, keeps the rust off tools, keeps the garage smelling fresh. Easy install, just goes through an exterior wall like a dryer vent, and needs to be within 1 foot of the floor.
http://homehardware.ca/en/rec/index...Ntk-All_EN/R-I3824952?Ntt=garage+dehumidifier
http://homehardware.ca/en/rec/index...Ntk-All_EN/R-I3824952?Ntt=garage+dehumidifier
good suggestion, will do.
not tied to road drains. i'm in the boonies, have a septic and a few leach fields. one drain ties into half the house downspouts and flows into a field in front of house. the other half flows out to the back. i can see the 4" "t" junctions where it all ties together. i just don't know where it goes from there, as it runs underground.
ain't home ownership fun?
not tied to road drains. i'm in the boonies, have a septic and a few leach fields. one drain ties into half the house downspouts and flows into a field in front of house. the other half flows out to the back. i can see the 4" "t" junctions where it all ties together. i just don't know where it goes from there, as it runs underground.
ain't home ownership fun?
As a follow up to this thread, does placement of dehumidifier matter? Meaning, could I place it in any part of the garage and will it pull moisture equally?
I have one spot on opposite side of garage (from where there typically is more moisture) and where running a drain to the exterior would be ideal.
I have one spot on opposite side of garage (from where there typically is more moisture) and where running a drain to the exterior would be ideal.
pseudorealityx
Well-known member
Ideally, you want it in the warmest, wettest location possible.
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