Attic Ventilation

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  #1  
Old 11-29-16, 06:46 PM
J
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Attic Ventilation

We recently (1/16) bought a new house about 20 years old, but when the inspection was done there was extensive mold in the attic mostly on the south side.

After a battle with homeowner and mold company it was re-mediated in march of last year. They removed all the baffles in the attic and stated that some of the insulation was too far forward blocking the baffles in the soffit. The bathroom fan was also looked at and working correctly venting through the roof. The house has a ridge vent and looks ok to me in the attic, about 4" wide.

I went up in the attic tonight and for the most part it looks ok, but it's still early in the heating season and I did notice some areas where it looked like the mold is coming back. It also doesn't feel very airy up there either, I know in my last house when I was up in the attic I could feel the air moving around up there. There was also some spotty moisture up there on the insulation.

My plan at this point is to watch it closely, but looking to see if I'm missing something here?

Thanx
 
  #2  
Old 11-29-16, 07:41 PM
B
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Hi johnboy,
Sounds like you still have a problem. Step one is to seal all air leaks from house to attic, the house is where the moisture comes from, unless you are in a very humid location.
Step two is to verify you have adequate ventilation. Soffit vents have a net free area rating that tells you how much actual vent area they represent. Describe what you have or post some pictures. And of course they need to be open to the attic. As for the ridge vent, even though you can see that the sheathing has been cut back it can still be an issue that they covered the top with underlayment and forgot to go back and cut it out. Happens far too often. Some form of smoke could be used to test to see if there is any air flow going out the ridge. None of my friends smoke cigarettes any more so I use a smoke pencil, but a punk stick or incense stick will work also. Ridge vents can be poorly installed as well and greatly reduce the air flow.

Double check bath fan ducts and same for the kitchen fan.

Last is to address the moisture level inside the house. If it is really high that increases the moisture level in the attic.

I've added a link about air sealing.
https://www.energystar.gov/ia/partne...ide_062507.pdf

Bud
 
  #3  
Old 11-30-16, 04:06 AM
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Bud is right on with sealing. Attic ventilation is a natural process, so when the baffles are blocked air must continue to flow and leaks begin from within the interior. Seal as best you can, including the bathroom fan.

Also, make certain the baffles and soffit vents are sufficient for the house.

Finally, inadequate insulation may also lead to moisture issues.
 
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Old 11-30-16, 05:57 AM
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All,

Thanks for the responses, I'll pursue these suggestions and post a follow-up. I'll also post some pics for evaluation.

Part me feels this house has always had a ventilation problem as it looks like most of the plywood in the attic was changed when the roof was done several years ago. The plywood is already delaminated in many areas.
 
  #5  
Old 11-30-16, 07:27 AM
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Since you suspect the attic moisture (ventilation issue) has been an ongoing problem I would look for some of the major bypass areas that provide a path from house or basement directly to the attic. 20 years ago they didn't pay a lot of attention to what we now know are common problems. In that link you will see the chimney chase, plumbing vents, recessed lights, and all sorts of electrical penetrations, but the big ones I have found deal with framing errors and are hard to see unless you can see through the walls.

Examples, a front porch may have been built without the plywood sheathing covering the frame of the house. Or dormers or a stairwell built where the studs provide an unexpected air path.

If you go into the attic and look around, watch for dirty insulation, especially if it is fiberglass. Air leaking into the attic will deposit years of dust as a telltale sign of an air leak.

If you want to kick it up a notch you can rent an infrared camera and during the cold season any leaks into the attic will glow with a heat signature. Just be sure to close the access hatch behind you. The next step up from that would be to bring in an energy auditor (I'm one of them) and have them do the infrared searching for you while pressurizing the house with their blower door equipment. The rest of their report can be very useful as well.

Bud
 
  #6  
Old 12-05-16, 04:01 PM
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Just a quick follow-up on some things I've looked at it:

Noticed the attic hatch didn't have any insulation on it and around edges were not insulated. Also sealed gaps around bathroom fan. Other than that not a lot of intrusions into the attic. I didn't see any dirt on the insulation up there indicating a leak.

As far as the house it's standard 2000 sq. ft. colonial. The only addition that was done several years ago was removal of one of the garages for a family room. The soffit vents are 8" wide and ridge vent was tested with smoke and appears to be working.

At this point I know what I'm starting with and will monitor every few weeks for now. Any further mold growth I'll call an energy auditor as Bud suggested.

Thanx

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  #7  
Old 12-05-16, 05:08 PM
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Nice house. I spent a few years in NJ that style was very popular.
One observation, the overhang in the front where the second story extends out past the first floor wall creates another soffit which needs to be sealed tight. Any leakage there may have access to those extended floor cavities and then all interior walls. I said "may" as the builder might (rarely) have added some solid blocking above that wall.

Bud
 
 

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