Attic condensation and roof vents

Old 02-09-04, 08:54 PM
Wayne Liko
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Attic condensation and roof vents

I have two questions but first some background.

I live in a custom built, 3 & 1/2 year old, two storey home. The attic is insulated with blown cellulose (R40 for the most part; more on that later), with a vapor barrier below that. I have vented aluminum soffits and 4 or 5 roof vents. My laundry exhaust runs through my attic, and vents out the bottom of the gable end of the roof. The vent is insulation wrapped under the blown cellulose. The only other vent through the attic is the plumbing. The furnace and HRV vents exit just above ground level. This fall I added a humidifier to my mix of furnace and HRV system. The humidifier has an external sensor to automatically adjust to the exterior/interior temperatures.

Within the last 7 to 10 days, I started hearing a drip coming from my attic hatch, located in a bedroom closet. I popped it open and noticed frost across a good portion of the roof, mixed with some condensation and, of course, water dripping. The most significant water dripping was occurring right over the hatch but it was not the only place. It should be noted that most of January, we saw temps in the -15 Celcius all the way down to -40 Celcius. The sun made an appearance the day the drips began and temps start to climb towards the freezing mark. Iíve been through two winters in the house without these issues.

First question: Can this problem be linked to the new humidifier; is there some link between the increased humidity in the house and the attic problems?

I called over the roofing contractor for a look see. He told me that there should not be any frost or condensation and he felt there wasnít enough attic insulation.
So I call the insulation contractor; he tells me Iím losing significant heat through my attic hatch because it is not as snug as it could be. There seems to be about an inch of dead space in both the length and width but otherwise the hatch has insulation foam on top. And if that is the case, why havenít I had these frost/condensation issues the previous three winters?
I did a walkabout in the attic and measured at various spots. The depth is anywhere from 12Ē down to 7Ē in spots. I would average it out to 9Ē. The insulation contractor tells me the R40 blown cellulose depth settle should be about 10 & 1/4Ē. It seems to me that Iím going to ask him to level it out but, again, why didnít I have these problems the last three years?

Second question: During my attic rounds, I noticed damp spots in the insulation (and a couple of spots had traces of snow) below the roof vents. Is it normal for condensation or snow to come from the roof vents or is this a symptom of another problem?

Iím resizing and re-insulating my attic hatch. Iím likely going to get the attic insulation leveled out. Does anyone have any thoughts or ideas on this matter? Any help would be greatly appreciated.
Old 02-14-04, 01:37 PM
Ed Imeduc's Avatar
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Location: Mountain Williams Missouri
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You have a lot of ifs here. first dont know code there . For if you do have the sq" vents that you need for the home also like 1/2 in and 1/2 out.

Next you put a humidifier. Here we go for one thing. External sensor. That Id cut out first and just control it from the inside

Attic hatch. They now have like a insulated box that you put over that hatch and box it in . you just open it when you want up there.

Your insulation up there 9" to 12" not to bad . But what you want to look for in any blown insulation like there in the attic cellulose or other. Make a box12"X12" open top and bottom out of metal if you can about 16" deep. Now push it down in the insulation. Dig all that insulation out and put it on a scale. This will tell you if they got to you on the insulation. I dont have the books on it here so I cant tell you what the weight should be. but thats how you tell good or bad.
Just off the top here to much humidity and fix the hatch, box it in. Then see if you have enough wents up there

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