Thread: Attic Moisture

Greetings from the Northwest (Portland area)... I'm new, I'm green (see my first post in the "introductions..new members" area)... but I have been a "voyeur" of inspection news for quite awhile and want and need your expertise... Besides learning and working on home inspections (30 or so) with an inspector of over 20 years I'm baffled (and so is he) on this attic that is way too wet. This is a custom home (3,500 sq ft) neighbor, that I have been doing "handyman" work for a couple recently moved from So Cal (the only people that can afford to buy here these days...hence why I may not be able to actually break into home inspection like I want) that was built in 99 and has the original shake roof. The roof is definately nearing it's end (we all know how newer cedar shakes don't compare to the "old growth" shakes as far as life span, right?)... Even though the new owners were skeptical of the roof, it has had a "roof cert", has been inspected by four different home inspectors, an independent roofing company, an HVAC technicial and a mold specialist. The roof does NOT leak and has not in the past. Ventilation was then brought up. But this house has more than enough ventilation (soffits and roof) and all are clear. Then there was the bath exhaust fans in question. However they are all well installed and the owners even quit using them for two weeks to see if that helped - nothing. There was the furnace as a question.. but the flue/chimney is perfect and it is no more damp there (or less than anywhere else in the attic). Then the crawl space was addressed... it's bone dry (and has remained that way). The first red flag was when we found out that the roof had been "power washed" prior to the sale. So we all jumped on that band wagon! And actually, the new owners had put fans up in the attic and we had dry weather for two weeks straight.. I got up there again and everything seemed much drier.... it was done... it was good, it was dry! No more moist, wet insulation, the ducts that had "perspiration" all over them was gone, etc. Then a few days later, we just had very heavy rains (you may have seen it on the news). I got back up there yesterday and it is back! It's damp, perspiration and moisture in the insulation, droplets all over... it's the same as prior, just as bad as before... and yet still, no evidence of roof leakage anywhere..... I know it's the northwest, but an attic should not be wet! None of the other attics that I have been in, here, are like that... mine is totally dry, every expert agrees... it should not be wet.... so why is it? Any ideas? I don't have pictures, but can certainly get them tomorrow and post them (and believe me, even a bad camera will illustrate what I'm talking about.... it's everywhere up there, uniform and throughout. I'd love to learn and figure this one out........

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What have been the temperature swings in your area? I am in a northern climate and have had a condition we call attic rain. During a cold spell moisture making its way into the attic, via attic by-pass, freezes on the the nails and framing. Then, when we get a quick shot of warm air, all this ice thaws resulting in a soaking wet attic.

Does the home have a lot of reccessed cans? Another source can be soffit drops that have not been properly draft stopped. I would also look the stair case ceiling over. If it has been pitched it also may be lacking any draft stopping.

This is a shake roof and not a shingle roof correct? Just thingking that if this is a shingle roof it should be on spaced out roof boards to allow the shingles to dry. If this drying process woud be working in reverse it may be adding to a high moisture level in the attic.

Quit guessing... enough of that has already been done several times over (it sounds like). Time to get out the big guns and have some thermal imaging done.

It does sound like that the problem is related to condensation being caused by an attic that is being supplied with alot of heat. The source of the heat should be determined and detected to find out what part of the home is leaking such amounts.

It certaily sounds like the heat from below is condensing the cold/ wet / saturated shakes above and causing the moisture issue. Find the heat loss and you find the source of the problem.

Rich

Originally Posted by Chris Yahn

Greetings from the Northwest (Portland area)... I'm new, I'm green (see my first post in the "introductions..new members" area)... but I have been a "voyeur" of inspection news for quite awhile and want and need your expertise... Besides learning and working on home inspections (30 or so) with an inspector of over 20 years I'm baffled (and so is he) on this attic that is way too wet. This is a custom home (3,500 sq ft) neighbor, that I have been doing "handyman" work for a couple recently moved from So Cal (the only people that can afford to buy here these days...hence why I may not be able to actually break into home inspection like I want) that was built in 99 and has the original shake roof. The roof is definately nearing it's end (we all know how newer cedar shakes don't compare to the "old growth" shakes as far as life span, right?)... Even though the new owners were skeptical of the roof, it has had a "roof cert", has been inspected by four different home inspectors, an independent roofing company, an HVAC technicial and a mold specialist. The roof does NOT leak and has not in the past. Ventilation was then brought up. But this house has more than enough ventilation (soffits and roof) and all are clear. Then there was the bath exhaust fans in question. However they are all well installed and the owners even quit using them for two weeks to see if that helped - nothing. There was the furnace as a question.. but the flue/chimney is perfect and it is no more damp there (or less than anywhere else in the attic). Then the crawl space was addressed... it's bone dry (and has remained that way). The first red flag was when we found out that the roof had been "power washed" prior to the sale. So we all jumped on that band wagon! And actually, the new owners had put fans up in the attic and we had dry weather for two weeks straight.. I got up there again and everything seemed much drier.... it was done... it was good, it was dry! No more moist, wet insulation, the ducts that had "perspiration" all over them was gone, etc. Then a few days later, we just had very heavy rains (you may have seen it on the news). I got back up there yesterday and it is back! It's damp, perspiration and moisture in the insulation, droplets all over... it's the same as prior, just as bad as before... and yet still, no evidence of roof leakage anywhere..... I know it's the northwest, but an attic should not be wet! None of the other attics that I have been in, here, are like that... mine is totally dry, every expert agrees... it should not be wet.... so why is it? Any ideas? I don't have pictures, but can certainly get them tomorrow and post them (and believe me, even a bad camera will illustrate what I'm talking about.... it's everywhere up there, uniform and throughout. I'd love to learn and figure this one out........

Hi Chris and Welcome!

First, your post is hard to read. Try paragraphs the next time, it really helps to break it up.

As for the moisture in the attic. It really sounds like a ventilation problem. Either too much air (wet moist air) is being sucked into the attic or the moisture from the water soaked shingles is not being vented out of the attic.

What type of insulation is in the attic?

What type of deck are the shakes on?

You said the house had a "Roof Cert" who and what is this and who did it?

Power washed shake shingles? This is a No No!

My thinking is revolving around the shake roof as being part of the problem.

Chris,
Simply having ventilation will not solve the issue. The ventilation must be installed correctly and it must be balanced. What typo of roof is it, hip, gable ect??. Where are the exhaust vents, are the on the same plane, same line, what type are they, are the the same type. Is there a balance between intake and exhaust? If not is there more exhaust or more intake? Too much exhaust and not enough intake can make a negative system. Mixing exhaust types or installation on different planes, or height lines is bad also. It is estimated that 90% or more of roofs are improperly vented and this voids the manufactures warranty for most major shingle manufactures.

The amount of moisture given off from normal usage in the home is enormous and given homes are sealed better than ever, moisture is a constant issue. It is common for this moisture to work its way into the attic space and without proper ventilation that is where it stays.

There are good web sites that can help with that regarding venting manufacturers documentation. I have some but not with me at the time, on the road. If the venting is installed correctly (doubt so) then there must be a source of moisture, from the inside.

Here is one thing you can try, it might help determine where the problem is coming from (it could also be from both sources):

Attach some plastic sheeting to the underside of the rafters or top chords, covering a large section of the roof.

Go back a few days later and see if the condensation is on the underside of the plastic sheeting (moisture from below - i.e., from the house) or on the top side (moisture from above).

From there you could try other experiments with the plastic, covering a large section from the soffit vents to the ridge vents (if installed) thereby ventilation only the roof in that area, not the attic, see what effect that causes/has.

Chris:

Is this a slab home or is the attic space have the plumbing lines, pipes will sweat and cause problems.

Also newer forced vent furnaces will cause condensation (as well as water heater flue pipes).

Try these items

Rolland Pruner

Hey... great stuff, thanks for all of your suggestions, tips and thoughts. As far as the attic status now, it's still wet. I set up another (larger) box fan and think that maybe the ridge vents are blocked or partially blocked with needles.
So I heading over to clear those. As far as your questions, I did take some photos, which I think answer most of them.

I'll check back to see if you still have questions or additional thoghts and let you know just how badly the ridge vents were blocked.

Thanks again, this truly is on the job training at it's best, and "Inspection News" is an awesome tool for someone trying to break in to the biz...

Chris,

What is the second photo of ... an off ridge vent?

If it is, it is not very large. I'd start by doing a rough calculation of the upper free net vent area and the lower free net vent area, and then roughly calculate the attic area to see if it meets minimum ventilation requirements.