Attic shingle nails wet (condensation) - looking for list of solutions

[keeena]

Hi, Before I begin, I will note that I searched the NGs for this problem and found enough answers to get me started. I want to get some more input based on my specific problem. I just noticed this issue in Nov; I'm in MA and its easily below freezing @ night.

HOUSE INFO: Attic shingle nails are wet and many of them have droplets hanging/dripping from them.. House is 1.5 yrs old, colonial. R30 in attic, kraft-faced, facing living space. Facing is not tacked to joists, insulation is just stuffed in from the top. Ridge and soffit vents w/ soffit vent "ducts" (no blockages). I keep the heat fairly low in the winter (60*). No ice on nails. No rain in the last few days (and no snow yet). Never had icicles on the outside of the house last winter and roof seemed to have uniform frost/snow coverage.

I'm pretty sure its a condensation issue. I'm going to look at sealing up all openings: whole house fan, bathroom fans/ducting and lighting. I do remove the WHF in the winter and cover the opening w/ 2 sheets of foam insulation (4-5" thick tot.), but this is probably still leaking lots of air and hopefully the major culprit.

QUESTIONS: How significant of a problem is this? I don't have any water spots on my drywalled ceiling. I noticed it due to water drops on attic-side of the access panel (which is insulated and has a foam gasket).

Does this stuffed-in kraft-faced fiberglass normally create a sufficient vapor barrier? Or will I still have issues after super-insulating the items I mentioned above? I'd rather have taped

6mil vapor barrier across all the joists coupled w/ unfaced batts (prior to furring strips & drywall). I'm under the impression that VB should be continuous and right now its far from it.

Lastly, are there any other things to investigate which may help? I'd rather not redo the ceiling or add more insulation. I may want to add gable vents due to poor exhaust for the WHF (ridge/soffit doesn't cut it...another story). Would add'l vents help this condensation problem by naturally venting more attic air?

Big thanks,

-K

[JoeSpareBedroom]

Got a fan in the bathroom? Where does it vent? There are builders stupid enough to vent them right into the attic, with no hose to a roof vent.

[Speedy Jim]

Another is the furnace chimney. Combustion products can soak the chimney masonry with moisture which then migrates to the attic. I've seen cases where it was practically raining in the attic! A metallic flue liner solves that.

Jim

[jolt]

The two most common reason for what you describe are water in a crawl space or a whole house humidifier set too high on the humidistat. I've been in attics in the winter that you could use a raincoat and umbrella. If the RH (relative humidity) is very high in the house it will migrate to the attic, where it will condense on the cold decking of the roof.

Sealing up the attic won't help because the circulation of cooler, dryer outdoor air will lower the RH of air in the attic and would help with your problem not make it worse. Cooler air can not hold as much vapor as warmer air, so cooler air is normally dryer air.

[keeena]

To answer some of the posts:

I have 2 bathroom vents on the second floor. Both are ducted to exterior (I know because 1 of them was not; I had them fix this last year when I noticed it). But I will be taping the connections as well as sealing the fixtures against the ceiling.

The chimney does not run through the attic air space - its all exterior to the building.

No crawl space; its a poured foundation.

I have forced hot water heating only - no air ducts/no central air/etc...

Thanks for the suggestions so far! Thankfully none of these additional things seem to apply to my house. Any thoughts on my vapor barrier (insulation) question? Should this be happening given the current state of the attic as I've described?

-K

[Malcolm Hoar]

Sealing up that duct work would be wise, I think.

So where do you think this water is coming from? Clearly, it's coming from somewhere. I have a hard time imagining this is caused by condensation from the cold outside air. As I recall, the humidity is not terribly high in Mass at this time of year. But maybe this a beachside property?

Of course, you live there and know the situation far better than me/us. Do you think that moisture is entering via the cold outside air? If not, keep looking (really hard) for some other source.

[keeena]

Malcolm, I think the idea is that the air in the living area is working its way into the attic. It then condenses on the cold metal nails in the attic. Its doing this in a large enough volume to cause my problem. In most cases, it probably occurs normally with much smaller volumes of air and is normally managed via soffit/ridge venting (in a perfect world, no interior air would escape).

I noted a few things I can do to help seal up some holes. My concern is that I may not have thought of all leaks...on top of the fact that the attic insulation / vapor barrier may not be up to par. I'm waiting to see if someone chimes in on how my attic insulation was installed and if its sufficient.

I unfortunately don't have waterfront property. :)

-K

[marson]

Here are two more ideas:

paint with vapor impermeable primer. I know Ben Moore makes a version

crawl up in the attic and find as many "bypasses" as you can..i.e. plumbing vents, wires that reach into the attic, etc, and plug them with expanding foam.

[ND]

"keeena" wrote

I think this could be your biggest problem. I'm in the Great Lakes area, and have R-50 in my attic. I forget what they say about once you reach a certain R value, it isn't cost effective to keep piling it on, but I think it's about R-50.

Here's a link that you might like to try out.