Where is moisture in part of attic coming from?

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Old 12-19-04, 11:53 AM
jdaresta
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Where is moisture in part of attic coming from?

By chance working on another issue in an accessible part of my attic (measuring the second floor joist width) I happen to notice in a few spots yesterday some water drops periodically on the nails (which some had rust on them and others did not) through the decking. It was sporadic which ones had it and which ones did not. On the wood I notices a few spots that were dark much like mildew. there was one place that I could feel moisture on the decking, but not much. This section of attic is angled and on one side is the slope and the other is a wall that goes to a large upstairs room. Above this large room is the peak of the angle that meets a low sloping roof. the second floor ceiling and the peak/slope there is probably about 2 feet max space. The only way I can see this space is by moving the upstairs bathroom exhaust vent and sticking my head up. The slope that goes to the part of the attic I was in has gaps between the second floor celing insulation and the decking supposedly to allow air to move. Btw, the second floor roof is metal and other than gable vents on the sides the bathroom pipe vents there is no vents. There where before small box vents (similar to http://www.owenscorning.com/around/v....asp?ProdID=24). they were removed though as the metal roof installer said they were not doing much and they could cause leaks through the metal due to the slope being that steep.

Obviously I was concerned. My first guess was that it was exhaust from a 1st floor bath that its vent goes to a plastic tube that runs up the center of the house to the in accessible part (about 11ft). The builders back in 1968 I suppose venting it to the attic was a good idea or something. So I spent hours trying to figure how I could rework the vent to somewhere else. After several tries of vents and such I gave up and put the old one back and I am calling the metal roofer to find out about adding an exahaust vent. However, I am not sure the exhaust is the culprit. Today I went into this area and there was no moisture at all. This time it was nice and dry. What also made me wonder if it was the exahaust vent is that in the inaccessible area when I peeked at it with flashlight and looked at where the vent should be coming up there is no mildew or moisture. FYI, the last shower in the downstairs bath was at 8am on Friday and I saw the moisture 11am on Sat.

So now I am confused. I do know the area I was at has limited ventilation and it is above two bedrooms. What is odd is that I would assume there would be moisture and such in the place where the exhaust from the bath goes, but there is none. Is it possible the moisture goes up, goes down through the tight squeeze of the slope into this attic space? Or could it be bad ventilation. This attic spot is backward L shaped and its on the longer part of the L. Its on the shorter end that there is a single gable vent. I do have a few soffit vents, but they are not the best. Until 3 years ago there were no soffit vents.

I guess my question is whether its possible moisture would travel from the top peak through the slope and collect? What other possibilities could there be to contribute to this? What should I look for?

Thanks.
 
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Old 12-19-04, 12:08 PM
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Sounds like you need some vents up there by the ridge for sure. Also get that exhaust fan to a vent up and out side the attic that is a no no. If he roofed it he sure can put a jack on there to vent that bath vents for sure.

ED
 
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Old 12-19-04, 03:40 PM
jdaresta
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Thanks. I left a message for the contractor and I plan to call tomorrow afternoon just in case.

One question I have though is what are the pitfalls of having vents cut into a metal roof. With shingles they usually lap over the top of the vent. How do they put vents on a solid piece of metal? Also, currently underneath the metal is the old tar and such roof with decking underneath. Any concerns I need to be aware of? Last thing I need out of all of this is any leaks.
 
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Old 12-19-04, 04:41 PM
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Hard when you cant draw it out. You have a 3" pipe. So you cut the hole a little over . Now how big or what kind of roof jack?????? So cut the hole in the metal so it would go around the outside of the jacks pipe. Then cut a slice in the metal roof across the center of the hole. "Running with the ridge" Now the top of the jacks flashing will slip under the metal roof and go up till its over the hole for the pipe the bottom part of the flash put roof cement under it and tack it down. Should hold. Do it all the time.

ED
 
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Old 12-23-04, 05:33 PM
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Normal Condensation

What you are exhibiting appears to be normal minor and intermittant condensation that occurs in all homes at various times thru thr heating/cooling season.

Anytime that the surface temperature of the roof deck or nails drops below the dew point for a given mass of air at a fixed relatively humidity, condensation occurs.

This condensation can and does occur irrelevant to whether or not excess mositure is present in the attic and can be spotty based upon the differences in temperature between surfaces in differing parts of an attic.

Moisture in attics is also not limited to being introduced simply by way of bathroom vents.

Any duct, chase, chimney, pipe, wire, cable door, hatch or other opening from the heated space below into the attic can allow in warmed moisture from the living space below.

Likewise, water is gas form will penetrate directly through walls and ceilings into an attic space...right through the drywall, plaster, studs and other permeable materials as it moves from high areas of concentration (heated moist interior air) to areas of less concentration (cooler attic air).

The type of condensation you are seeing is normal and can even occur in summer months given the right combinations of temperature and humidity.

Doesn't appear to be anything that needs to be treated and should be considered harmless and normal.
 
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