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Moisture in the attic.

post #1 of 20
Thread Starter 
I have an attic with about six inches of insulation over the living area. This past weekend I went up to check things and found moisture droplets on a plastic bag covering a portable natural gas heater I have stored there. The attic has three gable vents two of which are temporarily sealed for the winter, I also have pull down folding steps for which I made a box for out of rigid insulation. This was shortly after we both took showers so I know where the moisture came from (shower is vented thru the attic to one of the gables) and the heater was next to the stairs. My question is it better to leave the gables open so the humidity can escape?
post #2 of 20
Quote:
Originally Posted by squidder 329 View Post

I have an attic with about six inches of insulation over the living area. This past weekend I went up to check things and found moisture droplets on a plastic bag covering a portable natural gas heater I have stored there. The attic has three gable vents two of which are temporarily sealed for the winter, I also have pull down folding steps for which I made a box for out of rigid insulation. This was shortly after we both took showers so I know where the moisture came from (shower is vented thru the attic to one of the gables) and the heater was next to the stairs. My question is it better to leave the gables open so the humidity can escape?



Yes
post #3 of 20
Quote:
Originally Posted by longcaster View Post

Quote:
Originally Posted by squidder 329 View Post

I have an attic with about six inches of insulation over the living area. This past weekend I went up to check things and found moisture droplets on a plastic bag covering a portable natural gas heater I have stored there. The attic has three gable vents two of which are temporarily sealed for the winter, I also have pull down folding steps for which I made a box for out of rigid insulation. This was shortly after we both took showers so I know where the moisture came from (shower is vented thru the attic to one of the gables) and the heater was next to the stairs. My question is it better to leave the gables open so the humidity can escape?



Yes

+1

post #4 of 20
Lotta variables here. Does the fan vent to the one open gable vent? How long is the hose run? Is the hose insulated? Where is the fan motor? Gotta ask, any roof leaks? I dont know how big the attic is and how big the vents are but im thinking that blocking two of them is not the cause. If ya get a chance, take the two hot showers then go up to attic 20 mins later and look for condensation on hose, or any other cause. Good luck.
post #5 of 20
I agree with the PP, more ventilation isn't always the fix. Eliminating the source of the moisture always is.
post #6 of 20
Yeah, this time of year you're going to get condensation from any moisture that gets up there. I'd have a look at any ceiling penetrations (especially in the bathroom) to see if they are sealed, and inspect the fan ducting and any connections to make sure there are no leaks there.
post #7 of 20
6" of insulation seems light for this part of the country. Is that R19 when you should be over R30?
post #8 of 20
Thread Starter 
Thanks for all the responses, the sealed gable vents are at the east and west ends (west has gable fan) the unsealed faces south.They are about 12x20 inches. The exhaust fan is on the attic side of the bathroom ceiling with approx 15' of the silvery type flex lightly insulated and I did feel moisture on the vent hose.The house in mainly used in the summer and used on the weekends in the winter, the heat is kept at 52 when vacant. I will check around the exhaust fan itself for wetness. I was holding off on more insulation till we live there full time and the roof is one year old.
post #9 of 20
Adding more insulation without air sealing is kinda pointless. And it still wont address the moisture issue. That great stuff foam in a can is... well great stuff smile.gif.
post #10 of 20
The fan should have a damper where the air blows out, might wanna make sure its not stuck open. Also, if its blowing out through a gable vent i'll bet there is no louver cap. Maybe make a dedicated exit for the air either through the gable side wall or the roof. Going through the roof may allow for the shortest hose run which should help. They make roof caps for 4" hose. Could also get a timer switch for the fan that would allow it to run 10-15 mins after the shower is done. I have seen significant water inside the exhaust hoses in attics, moreso in long runs. Use as much rigid pipe as you can and pitch it out, if joining sections point the male out and check for water at louver. Hope this helps.
post #11 of 20
You need to see if your roof ventillation is BALANCED. Just because you have vents doesn't mean they are doing diddly squat. Look up roof ventillation on the GAF site.....You need the sum total of the intake at the soffit to equal or exceed the vent at the ridge.

Trust me....I had the same issue you had and it cost me alot of money because I had to have 80% of the Plywood replaced from rot when I did my roof. You need to have a balance between intake on the soffit and exhaust at the roof peak. As soon as you comprimise convection, the roof ceases to ventillate and you get moisture build up and rotting wood.

What I have now is SV-10 intake vents at the soffit and an appropriate and matching ventillation at the ridge vent. No many roofers know about this and think a gable vent and/or a fan is gonna fix things and there dead wrong because I had both.

Check out this video...I didn't use this product, but it explains what you need.
post #12 of 20

Unblock your attic vents. They're probably too small anyway especially if they have screens (50% drop in effective area). The vents are there to solve the problem you're having right now. I may have missed it in the previous posts but your bath fan needs to vent outside and not in the attic even if it's right near a vent.

post #13 of 20
Thread Starter 
I really appreciate all of the knowledgeable response, it is really great how many people extend themselves to help someone else they don't even know. I'm going to do a little experimenting with vents blocked and unblocked , the situation isn't critical now but when we become full time shore people it will need to be resolved. I'm aware of the damage moisture can do as I know some one who had his roof rot. Thanks again.
post #14 of 20
As Ed has mentioned, start by eliminating the source of airflow from the living space into the attic. Fiberglass batt insulation will not do it. To find air leaks, pull the batts back and look for obvious penetrations (Pipes, wires, wall plates etc) and fill them with foam. If the air leak is bad enough, your insulation will be darkened by dust-laden air moving through it...check out this doozy from my attic. I recommend purchasing a foam gun and cartridge cans over single cans of Great Stuff because the the gun allows you to shoot some here, some there, close the valve and do some more in a week etc....Great Stuff cans require you to shoot the whole thing in a short time, otherwise the dispensing straw will gum up. Only after you have sealed all penetrations, and I do mean all, should you move on to ventilation which, IMO, should only be needed in the summer to vent super-heated air out of your attic. It should not be needed to vent moisture-laden air in the winter as you are literally paying to heat the atmosphere.

post #15 of 20
Thread Starter 
The past weekend I was the only one at the house, so when I showered I kept the bathroom door shut and ran the exhaust fan as well as opening the window. I let the fan run while I dressed when I went to check the attic there was a lot less moisture. Our pull down attic stairs are directly outside the bathroom door in a small hallway so I believe they are the majority of the cause and I'm going to make them more air tight. I'll work out from there including having the bride keeping the door shut, she likes it open to lessen the steam in the bathroom.
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