Home>Discussions>INSULATION & HVAC>How to increase attic ventilation on one side
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Timothy Miller
Re: How to increase attic ventilation on one side

Howdy there may be enough venting. you may be having back up water from ice damming on the bottom of the north slope how far up the slope of the roof is the wetness? Do you see any bump in the roof snow t word the bottom edge of the roof an is there a rain gutter that may be full of ice on this north slope.

bp21901
Re: How to increase attic ventilation on one side

The wetness goes from the ridge down to just above where the styrofoam air channels terminate at the eave. There is no moisture within the space covered by the air channel which leads me to believe the air flow is there and maybe the styrofoam keeps the moisture from condensing on the roof deck.

There is no ice dam on the N side. I use a snow rake to pull the snow off the roof (on all sides) up past the eave line. This allows any that does melt to make it into the gutter without damming up over the eave space. There is minimal ice in the gutter, it is no where near full.

Timothy Miller
Re: How to increase attic ventilation on one side

Howdy, odd i have inspected thousands of roofs not seen this type of issue . So how many feet of venting does the ridge cap and the eve vents have? Read today it should be the same amount? When did this wetting of the roof decking first occur?

Timothy Miller
Re: How to increase attic ventilation on one side

Howdy one last time. Awoke thinking this over. The bathrooms got exhaust fans? Are they run after shower/ baths 15 minutes? are they vented threw the dwelling to the outside or into the attic? they need to be threw to the outside. How many plants are you growing in the home as this much moisture in the attic is likely due to too much humidity in the home what is the moisture level in the air? If furnace has humidifier turn it off. Lots and lots of plants? Good luck.

canuk
Re: How to increase attic ventilation on one side
bp21901 wrote:

There are bedrooms and a hallway under it. Other side is bedrooms, but no hallway. This is an addition to the original part of the house and makes the structure an L shape. The prevailing winds run W to E parallel to the ridge of the addition where the moisture is on the N side of the roof. There is a noticeable temp difference on the underside of the roof deck, I was up there the other day, its still damp-ish on the N side. There is about 4 to 5 inches of snow still on the roof on the N side and no snow on the S side from the sun hitting it. I had hung a box fan up in the rafters and have it on low trying to dry out the roof decking. I want to dry it out as much as possible before trying the foam board. Like you mentioned before, the issue is I won't be able to see the effect since the foam board will be in place.

C'mon down, we still have about 6-8" of snow, some bare patches where the sun hits regularly. Too early here for golf yet, although I have the putting green cleared off for practice. I'd post a pic if I could, showing the green with the piles of snow all around it!

Hmmm ---- thinking out loud here.
I'm thinking the winds might be the cause and effect here.

The winds coming from the W are creating a positive air pressure on the W side of the home.
When they blow over the roof line onto the E side there is a negative air pressure therefore reducing the positive gradient for the air stream needed for the venting of the N side addition.
This would be more so if the addtion was located on the S end of the existing home ......... if you follow me.

Just a thought.;)

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