Who can diagnose roof/ventilation problems?

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Old 01-08-09, 08:21 AM
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Who can diagnose roof/ventilation problems?

We have two straight lines of moisture running parallel to each other on the cathedral ceiling, starting where it meets the wall, in our bedroom. Now I think I see evidence of moisture on the wall on the opposite side of the room.

We've had a general contractor out who said it wasn't the roof, but the roof vents weren't large enough. However, he wouldn't fix it and the guy we called to fix it said it was due to condensation forming under the flexible bathroom vent hoses in the attic.

Now we don't know what to do. This problem only happens in the winter, so I suspect ice damming, but the first guy said no. The house is about 8 years old and we do have a more complicated roof line than most houses in our neighborhood. We first noticed this problem two years ago and haven't been able to figure out what to do.

Who should we call to diagnose/fix this problem? Do I call a roofer, another general contractor, or an HVAC company? I know this seems like a crazy question, but I really don't know where to start. This problem is compounded by the fact that 2 or the 3 people in the house has had health problems the last couple of years, and I'm starting to suspect a major mold problem due to this.

thank you.
 
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  #2  
Old 01-08-09, 10:01 AM
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It's not a crazy question at all, it's an entirely reasonable question, but unfortunately it's not one that has an easy answer.

One of the things I've come to appreciate doing moisture intrusion inspections is that there are often multiple contributing causes of a problem, and that sometimes no single trade created them, or can address them.

For instance in your situation warm moist inside air might be migrating from the living spaces below the attic (you describe this as a "cathedral ceiling", however your description makes it seem more likely that you actually have some attic space above it) and into unconditioned (unheated) spaces above (there is a relatively inefficient vapor barrier between conditioned on unconditioned space), it may be condensing on the bathroom exhaust vent lines because of poor design and/or installation (flexible plastic ducting is a poor insulator, and is prone to dip and kink, which can reduce airflow and allow the accumulation of condensed water within the lines) and insufficient or poorly designed attic ventilation may be contributing to the creation of conditions which promote condensation.

Who's responsible? Possibly, everyone involved in the various systems noted above.

Whose responsibility is it to diagnose and fix it?

That's a really vexing question - in my experience sometimes everyone you call out to solve this problem will diagnose it being within their purview.

When I'm called out to look at moisture intrusion problems (I'm in the inspection and diagnostic business, and I don't sell or install any type of product) my approach is to attempt to assess each structure on an individual basis and to suppress the tendency to jump to conclusions based on previous experience.

I start by looking at the entire structure from the exterior, attempting to locate sources of ventilation and exhaust, evidence of improper designer and/or installation (for example at flashings) and for exterior evidence of water intrusion or damage - frequently as result I will spot problems (later verified by infrared photography or direct moisture readings) the structure's owner had not yet noticed.

I then do a quick walk-through of the entire structure that's accessible without entering attic or crawl spaces, again I'm looking not only for evidence of problems but also for conditions that predispose a structure to moisture problems. Foe example I want to know if there are humidifiers present, or if there's evidence of moisture intrusion in the basement that might be migrating in the form of water vapor up wall cavities to the attic. At this point I'm trying to think of the structure as a system, not as an isolated collection of symptoms, because when there are moisture intrusion problems the symptoms sometimes appear at a considerable distance from the cause.

If moisture intrusion is present only on ceilings and/or the upper portion of walls at the top floor, the next step is an infrared survey of the top portions of walls and ceilings in the top conditioned floor of the structure. I note not only anomalies that suggest possible water intrusion but also those that suggest uneven or missing insulation, air infiltration (in either direction) and the like, noting their location in relation to features such as chimneys, interior walls, and heating and plumbing penetrations and recessed ceiling lighting so that that I can later identify their location of the attic. Again, you have to try very hard to suppress the tendency to jump to the "obvious" conclusion, if for no other reason than liquid water can travel substantial distances across horizontal paths such as electrical conduit, HVAC ducting and structural members such as joists.

The next step is to go up into the attic, and see if I can find systematic relationships between what I saw in the conditioned space below and conditions in the attic.

Even in a simple attic (for example a gable roof with no dormers, no attic flooring, and no interior partitioning) I often find multiple potential contributing causes of problems: conditioned air rising through poorly sealed scuttles, chases and other penetrations, poor insulation and vapor barrier practices, uninsulated ducting, bathroom and kitchen fans exhausting into attics and the like.

However many of these conditions will also be present in attics not displaying moisture problems, and you have to be very careful not to jump to conclusions about the proximate cause of the moisture problem below.

For example in your case someone has noted condensation on bathroom exhaust lines as a possible problem.

If the IR scan showed moisture in these areas and/or there is evidence in the attic in the form of either present elevated moisture levels or staining on or below the ducts, even if there are many other apparent possible causes of the moisture problems I would likely suggest starting by replacing the flexible plastic ducts with solid metal, properly pitched, exiting the attic and appropriate location via a correct termination, and insulated to to lower condensation.

Perhaps this will solve the problem, perhaps not.

But it would be a addressing a currently active potential source of moisture problems - a condition which should be corrected in any event - and it would likely the least expensive of the apparent possible causes to correct.

If you can't find some relatively straightforward proximate cause of the problem, then your job becomes tougher as it's often a matter of weighing the probability that a given step will solve the problem against the cost and difficulty of making the change, and at this point to a certain extent you do have to fall back on experience.

For example if I observe rusted nails and widespread discoloration on the underside of the roof sheathing on the north side of the property in my climate, I know that some combination of elevated attic moisture levels and insufficient attic ventilation is likely cause.

However the "best" method of correction however is not always apparent.

For example if there are recessed lights in the ceiling below (a common pathway for conditioned air to to enter the attic, especially if they're located in a kitchen or bathroom) I look for evidence of increased discoloration at the sheathing above the lights, the same is true of other sorts of penetrations as well.

If I see this kind of localized discoloration in addition to the generalized discoloration on the north side it's possible that reducing air infiltration at these locations may be sufficient to substantially reduce condensation on the attic sheathing even if other problems (for example poor attic ventilation) are still present.


Fig 1. It's possible that reducing air infiltration at this point will be sufficient to lower attic mositure levels to the point where condensation is no longer a major problem.

A roofer looking at the same attic may know from experience that improving the attic ventilation will also substantially reduce condensation, and if he or she recommended this solution they would not be "wrong", it just might not be the most cost-effective way to solve the problem - and unfortunately there is often no way to determine which solutions will "work" except by attempting them.

This is a situation in which you now find yourself, you have various tradespeople differently diagnosing the problem, and suggesting different solutions, and much or even all of their advice could conceivably be "correct".

And the best advice I can give you is to listen to them, try and separate out the people who make sense from the people don't, and if there are multiple possible "reasonable" causes, to attempt to resolve the inexpensive ones first.
 

Last edited by Michael Thomas; 01-08-09 at 11:52 AM.
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Old 01-08-09, 11:48 AM
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If you could upload and link pictures of your problem (and if assessable. of the attic above) and link to them, that would be very helpful.
 
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Old 01-08-09, 05:49 PM
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Water Intrusion

Get a infrared thermographer to turn his camera on for you and that will take you to the source of the problem without question.
 
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Old 01-08-09, 06:28 PM
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Originally Posted by bkopps View Post
Get a infrared thermographer to turn his camera on for you and that will take you to the source of the problem without question.
I'm a pretty good thermographer, but I'd never claim that I can locate the source of every leak "without question".
 
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Old 01-09-09, 06:46 AM
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thanks, I'll try to get pictures this weekend.
 
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Old 01-12-09, 03:10 AM
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bathroom vents not being properly routed to your homes exterior is a big mold source (because they provide heat,and moisture) if left alone,and mold is life threatening,SO make sure it`s taken care of properly-the bathroom vents must be vented to the outside---otherwise we could use some pics to see more,and one or two of your ridge/clerestory venting at the top of that cathedral ceiling---also "parallel" to ridge,roof rafters, what ?
 
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Old 01-15-09, 06:59 AM
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the bathroom exhaust is vented to the outside. we had a roofer out this week, he couldn't get on the roof due to the weather but spent a lot of time in the attic. He said ventilation looked fine and saw no evidence of mold or even moisture! He's sure it's the ridge vent and also there's a leak around the fireplace. He'll come out again when the weather's more clear. We'll also get an HVAC person and, hopefully, a good house inspector out. Still working on the pictures. Thanks.
 
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