Condensation on Attic Air Vents/Baffles

[jmsajan]

I have read most of the posts pertaining to my issue, but still have a few questions unique to my situation. I live in Michigan and have recently added an addition off the back of my two story tutor home.

Background The existing second story roof pitch was continued rearward to create the addition roof. It is a 12:3 pitch--not very steep. The existing attic appears and always has appeared very dry to me. It has about

3"-4" of blown-in insulation. It has two side vents and two roof vents. There is a bathroom fan on the second floor but I have it vented into one of the side vents.

Because I extended the existing roof pitch onto the new addition it created very little space for insulation and air venting. I put soffit vents along the entire eave/over hang. I then put those plastic air vents from the soffit all the way into the existing attic space. I then put 5-1/2" R-21 insulation with vapr barrier facing the interior. Because I am working only with the depth of the joist I literally have roof board/air vent/insulation/drywall all stacked on top of eachother. The only air gap is the one created by the plastic air vents.

I was getting ready to drywall when I noticed serious condensation on the flanges of the air vents--the area where you staple. The area of the air vent that is off of the roof is dry but where the flange goes up to contact the roof board it is really wet. Not just like a little condensation where you could write your name, but like many big drops of water. My insulation was wet. I have ten "runs" and they all have this same condition.

Any suggestions on how to resolve this issue? Somebody told me that I need to have equal amount of inlets as I have outlets. I probably have more inlets then I do outlets. Should I install an attic fan? I was reading about a solar powered one, which means it only operates during the day, would that be sufficient?

[buffalobill]

[marson]

then browse thru the search feature and don't forget climate when you

first of all, what kind of vapor barrier do you have? you should have

6 mil poly, seams taped and all penetrations sealed. that alone should go a long way in preventing trouble.

second, it sounds like you have a lot of moisture in your addition. did it rain during construction or something? if so, you might want to try to dry it out for a bit.

finally, a better way to vent a roof is to use a cardboard chute which are available here in the midwest. this staples onto the joists and leaves a continuous air space unlike the foam chutes which just leave an air space in between two joists.

[jmsajan]

My vapor barrier is just the paper on the back of the owens corning pink insulation. Could you explain a little where I put the 6 mil poly? Do I put it between the insulation and drywall? Do I keep the paper on the insulation then? I actually constructed the addition in June and it never rained on it. But I added the air vents and ceiling insulation maybe in the last three weeks. I did not have any condensation/water issue until then.

Cardboard chutes, I have not seen them before. I just did a quick google and all I got was Chutes & Ladders game. Any suggestion where I can get them?

[marson]

yes, you need to staple the poly on the joists between the insulation and the drywall. it is fine to leave the paper in place. i would not cover up wet insulation, though!

i get my chutes at a large lumberyard that caters mainly to contractors. forget home depot and the like. it may not be necessary....i think your lack of an efffective vapor barrier is your problem.

also, the humidity in your house could be from your normal activities--cooking, showering, and the like. do your windows fog up?

[PeleSajan]

The windows on the second floor during the winter months are seriously wet. I have stormer windows and some become a little wet and foggy while others develop into a thich solid sheet of ice. I can not even see out the window through the ice. I can not even slide the stormer window up because the ice has sealed over the levers. These are very old wood windows with the rope and weights that are in bad shape. We have redone the upstairs bath and put in new windows--no fogging issue on these. I also installed an exhaust fan and we always run it when taking a shower(it is vented out of the attic).

Question, if I install the vapor barrier as you describe, it seems to me that the moisture will collect on the interior side of the 6 mil poly and soak my drywall??

[marson]

your insulation should keep the back of the drywall warm enough to prevent condensation. condensation usually happens in the back of the joist cavity, where the air temp is below the dew point.

sounds like you have excess moisture in your house. do some research about the sources and cures. the building science website referred to by an earlier poster is an excellent resource.

[Shirazois]

Sounds like you have warm air coming from somewhere around those vents.

We have the same problem with our back bathroom especially now that the ceiling is open from having a new roof put on and us taking off the interieor drywall ceiling. We have new pink insulation up there, but until the room is completely inclosed, we have to treat it as an OUTSIDE room, I close the air vents and keep a window open, and close the door to that room with either air conditioning or heating in on in the rest of the room

condensation is when warm air meets cool etc. Bathroom plumbing vents, air vents or doors can be the culprit but sounds like your pulling in warm air or vice versa thru those new vents.

Close those vents for now until you f> I have read most of the posts pertaining to my issue, but still have a

[PeleSajan]

Thank you to everyone. I have pulled down the insulation to let it dry. I am going to install a solar attic fan. I am going to install the 6 mil poly although I feel that I have to remove the vapor barrier from the insulation. I am going to do a trial over a few joists and wait a week to see if it resolves the situation. Do you guys/girls feel a week is sufficient?

Also, I started thinking about the sources, so I checked my furnace humidifier and it was turned up to almost 40. So I lowered it down to

1. This should help.

Any ideas how to do the vapor barrier around can lights?