Attic nails dripping

[Gntry]

I live in western NY and the weather here for the last week or so has been around low 30"s, I was in the attic the other day and the nails coming through the roof are dripping water....I have a full ridge vent, full soffit on the west side of the house(and they aren't blocked by any insulation), and gable vents. It is definately cold in the attic and there is about R25 on floor w/ barrier down towards living space, the roof was replaced about

10 yrs ago....what is causing this and should I be concerned?

[Speedy Jim]

Might not be your cause, but I had a similar situation that defied explanation. It was so bad that at times it was practically raining in the attic!

Turns out that that the gas furnace was the culprit. It vented into a brick chimney which had a proper clay flue liner. The chimney was in the center of the attic space.

The original monster furnace had been replaced with a much smaller unit and, I surmise, flue gas temps inside the chimney were now low enough to cause more condensation. This moisture could actually be seen weeping out of the brick mortar joints.

A metallic liner for the flue cured the problem.

Jim

[Don Phillipson]

First, find out whether this is moisture traveling along the nails from the roof top surface to the under side, or condensing from the interior attic air onto the surface of the nails (cooled by their heads through the sheathing.)

[Trajen]

Just guessing but.... I suspect the cause is why a cold glass of beer sweats on a hot summer day. The nail is much colder than the warmer attic air. When dewpoint gets close to temperature you get visible water vapor. Try a small fan to get the air moving. Again, only a guess.

[Roger]

Haven't experience that, but guessing it may be simple condensation. The nail conducts the cold from the base of the shingles, and if you have a warmish, humid attic, it will condense, just like on the inside of a single glazed window on a cold day. Perhaps your attic needs more ventilation to lower the humidity.

[bill allemann]

might be condensation. the nails would be at somewhat lower temp than the surrounding materials. is attic vented? any exhaust from the living space vented into the attic instead of outdoors?

bill

[CJT]

I think he covered that!

[Doug Kanter]

Maybe a bathroom fan whose duct is leaking moist air into the attic?

[CJT]

I think you need to quantify "cold in the attic." Put a thermometer up there. It could be pretty cold and still be warm enough for the nails to be a lot colder. Everything's relative when you're talking about relative humidity. :-)

In fact, you could probably also directly measure the humidity up there with a cheap hygrometer (although I don't know how good they are at cold temps).

Is your furnace in the attic, by any chance?

Could there be gaps in that moisture barrier, perhaps around light fixtures, vent pipes, etc., that are leaking enough conditioned air to carry the moisture you're seeing?

Can you discern whether some are dripping more than others? The worst offenders might be nearest the source of moisture.

I would be concerned, particularly because of the possibility of mold developing.

[barry]

Roger that, Roger, on the moisture condensing. Under prev. owner, my house had a variety of air leaks from heated space into attic. Roofing nails, having their large heads very near the Great Outdoors and having much greater thermal conductivity than plywood deck, served as main points of condensation. Such that you could see pattern of staining around their protruding shanks in summer. Slowly fading now. And ... energy consumption waaaaay down.

OP might look for entry point(s) of relatively high absolute humidity air from below. They sure are there, and with chimney-effect it doesn't take a lot of flow-area.

HTH, J

[Bob]

Is it possible that the problem is caused by having the attic door opened? If you go up, is the moisture there when you first get there, or only after its been opened for awhile?

Bob

[Jane Cook]

I have a brand new roof. Has ridgevent, and there is a vent on one side of the attic. When it warms up I am getting water dripping from the nail sheath. What’s wrong? Who do I call?

[Marilyn Manson]

Sounds like excess moisture in the attic. I'd start with whoever put on the roof and get their opinion, although it might not be worth much, because

I'm not sure why there is a gable vent if they installed a ridge vent. It may or may not be related to your moisture problem, but it's not a good idea in any case. Are you sure that they didn't block the gable vent e.g. cover it with plywood on the inside?

[micky]

Too many steamy hot showers? Bathroom fan vent doesn't go all the way through the roof, or at least to just under the ridgevent?

Though I woudln't expect them to change yoru fan vent, maybe for some reason they did. Conceivably they moved it and forgot to put it back.

I have two vent fans that stop about 4" below the ridge vent, but I never take steamy showers. OTOH, I have 100 n'bors with the same house and probably half of them had the same plumbers and haven't heard any complaints.

What's the out side temp, how warm is the attic when you call it warm?

Except for double bulb and maybe sling hygrometers, they aren't very accurate, but even a cheap inaccurate one might give valuable information. Yesterday I put a thermometer/hygrometer in my shirt pocket under my jacket and a few minutes late the temp when from about

70 to over 80, and the humidity went from 40 down to 30. Later it was back up. It's the cheapest hygrometer Ive ever seen, but it does move.

Ghostbusters

[trader_4]

That covers the outgoing air, what about the incoming? Is there sufficient soffit venting? If there is venting, is it being blocked by insulation? Not unusual to see that, insulation guys shove insulation blocking the vents. They have plastic baffle like chute things that you can staple between the rafters to keep a channel free of insulation.

And like others have said, anything venting into the attic that should not be? Bath fans, dryers, etc?

[micky]

I had soffits that were largely blocked by milkweed. At least, I thought it was milkweed but it was something else. On the outside. Easy not to notice and though it arose during the summer, it didn't go away in the winter.

When I was on a ladder, I could peel it off like the lint on a clothes dryer filter.

I think a tree near my house fell down and it's not a problem anymore.

[Marilyn Manson]

Also not unusual for roofers to (correctly) say "If we're adding a roof vent, we also have to add soffit vents." Then they cut in the soffit vents but don't do anything about dealing with the insulation that was already there (or not dealing with it correctly, e.g. the baffles you mentioned, etc.)

When I had my roof done the roofer (a family friend) said to me "I've seen your attic. It's going to be a real PITA to put baffles in, especially during this heat wave. I'm going to have to charge you accordingly. Option 2: I'll toss in enough baffles for free and you can do it yourself in the evenings, when it cools down."

I took him up on his offer and he was right. What a PITA. Dirty, sweaty, cramped.

BTW...I built one of these to put over the drop down stairs. Works like a champ. Mine has such a snug fit that I added a couple of old cabinet doors handles to the underside of the top so I can just grab them and pull it down into the opening.