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Old 12-09-2012, 11:55 AM   #16
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Roof venting on colonial with no soffit


Hot moist air will disperse very rapidly throughout the attic, it does not stay on one end. We are talking about pressure here, and the temperature will constantly attempt to reach equilibrium. I suspect that what WOW says is correct. There is just enough of a difference on the north end to create the conditions you have. You may very well have hot air coming from somewhere else, considering the fact that someone dumped your bathroom vent into the attic. I am pretty darn sure that gable end venting will solve your problem, Scott. I had a home in North Jersey in which they dumped the bathroom vents into the attic. It had gable end venting, and never had a mold problem, but I had to install through roof venting due to a whole house inspection when I sold it.

PS They are Trusses, not trusts

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Old 12-09-2012, 03:22 PM   #17
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Roof venting on colonial with no soffit


I hope I'm wrong and just venting the bath fans outside solves your problems.

Gary
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Old 12-10-2012, 08:41 AM   #18
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Roof venting on colonial with no soffit


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I hope I'm wrong and just venting the bath fans outside solves your problems.

Gary

That is certainly the first thing that I would do to start with.
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Old 12-10-2012, 03:34 PM   #19
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I agree, that goes without saying. I usually site the Code requirements for bath venting but find it unnecessary as more members have read them from me here over the past 4 years... just as more accurate info is given on basement insulation and vapor barriers. I was looking at the mold on the roof sheathing, low down and close to the cellulose at the sloped ceiling area, hope it is not coming from there (no baffles pictured). If after bath fan venting; shows new mold, the OP knows where we are...lol.

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Old 12-10-2012, 03:48 PM   #20
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Roof venting on colonial with no soffit


Hi Gary,

It may very well be that a lot of that gray we are seeing came from that blown in cellulose when it was blown in against the underside of the plywood. I would personally never use that crap again as an insulation. It likes water.
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Old 12-11-2012, 09:40 AM   #21
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Roof venting on colonial with no soffit


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Originally Posted by GBR in WA View Post
I agree, that goes without saying. I usually site the Code requirements for bath venting but find it unnecessary as more members have read them from me here over the past 4 years... just as more accurate info is given on basement insulation and vapor barriers. I was looking at the mold on the roof sheathing, low down and close to the cellulose at the sloped ceiling area, hope it is not coming from there (no baffles pictured). If after bath fan venting; shows new mold, the OP knows where we are...lol.

Gary
I agree that it is a likely combination of issues. Poor venting (probably via obstruction and just a poorly designed roof venting layout/deployment) combined with additional moisture being dumped in the attic.

I have seen plenty of scenarios where bath fans are dumped in attics without manifesting mold growth. Never a good idea but if the attic if vented and other air loss/moisture migration is controlled, it usually does not become and issue.

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Hi Gary,

It may very well be that a lot of that gray we are seeing came from that blown in cellulose when it was blown in against the underside of the plywood. I would personally never use that crap again as an insulation. It likes water.
Gary has cited that idea of the hygroscopic nature of cellulose but I have never observed and issue with it in this climate and as you know, it gets pretty humid up here.

Here is the information I got back from the engineer at NuWool (of course he is going to be a bit biased):

There are no issues specific to cellulose insulation in high humid or coastal areas. Cellulosic insulation does not act as a desiccant pulling water vapor from the air but rather acts as the wood it originally came from. That is to say the moisture content will increase or decrease as a function of the relative humidity just like construction lumber. We have Nu Wool installed from Minnesota to Mississippi without issues.

I haven't found anything online (to date) with any concrete example of a moisture issue in a loose fill blown attic with cellulose.

It tends to form a bit of a skin on the top as it settles and I suspect that this might help with the moisture resistance at that level as it certainly helps with the air movement.

http://www.applegateinsulation.com/P...es/249224.aspx
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Old 12-11-2012, 10:38 PM   #22
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Roof venting on colonial with no soffit


"I haven't found anything online (to date) with any concrete example of a moisture issue in a loose fill blown attic with cellulose."-------- me neither, other than; if dense-packed, it needs to breathe if up against painted-tight siding- esp. on the S. and W. side due to solar gain as WoW said already; http://www.buildingscience.com/docum...oss-enclosures

I've seen a few case with exterior sprinklers hitting the brick veneer and moisture lifts the interior paint and drywall tape from the great capillarity of cellulose (moving the moisture (wicking) from source to other areas, fine if air-space next to it). It's not night-sky radiation as there are no soffit vents; http://www.buildingscience.com/docum...bout-diffusion

Scott, did you check the rectangular 3-1/4 x 10 (standard size for range hood ducting) to make sure those are bath fans? Very hard to run two (or even one) round ducted exhaust into a rectangle without getting a lot of condensation water in the duct opposite, at the transition joint- has to drain somewhere, IMO. I was concerned with the dark color (wet) of the plywood, all the way down to the cellulose in the left side of the pic. So, there are no baffles and the cellulose looses R-value by conduction touching the colder roof sheathing constantly. Any diffusion through the sloped ceiling wets the top layer of cellulose/plywood without any air benefit to remove same, do you have a vapor retarder/barrier next to the drywall ceiling?

Gary
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Old 12-11-2012, 10:45 PM   #23
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I did a full inspection of the attic. The duct leads all the way down to the crawl space. I removed it and packed insulation in the hole. I will vapor seal the opening in the crawl space. Both bath fan vents to the outside were laying in the attic so I will need to vent those outside.

Now the next step is to add in the gable vents, but I am hesitant to do so. I am afraid the gables will draw in rain and snow when used in combination with the ridge vent that is already installed. Will this be fine?

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