# Condensation on cathedral ceiling



## barbaraizac (Sep 20, 2009)

Last December I replaced the composition shingle roof on my entire house. The master bedroom & bath addition, built by the previous owners, had two layers of comp shingles that had to be removed. The master bedroom has a cathedral ceiling and the drywall is attached directly to the rafters, which I'm guessing are 2x6. I am assuming that there is some type of insulation between the two, but I have not yet drilled into the ceiling to make sure.

I live in Southern California and we have had a really hot summer. About three months ago, I noticed that the ceiling was wet about two feet above the skylight (installed in 1991). I immediately called out the roofer to check the flashing. It checked out okay and he told me that I must have a leaking pipe in the ceiling. Then I called out a plumber, and he confirmed that there are no pipes in the ceiling. The wet spot, which I believe to be condensation, is evenly dispersed over a 2x2' section. It appears overnight and then disappears during the day. I got the roofer to come out again two days ago and he installed an O'Haven roofing vent right over the trouble spot. It has failed to correct the problem. I went up on the roof with him when he installed it, and to my horror, I found that the entire section of roofing over the cathedral ceiling was damp. The rest of my roof (with a crawlspace below) was dry. When he pulled up the shingles to install the vent, the paper (felt) was dry.

My question is this: Why did this problem occur following the installation of the new roof? Is it possible that because there were two layers of shingles there before that they kept the heat down and prevented the condensation problem? If not, is it possible that there was some kind of insulation between the old roof and sheathing before that isn't there now?

Please help. I lost my husband to cancer recently and I am lost as far as what to do. I know I need to improve the ventilation, but no one I've talked to can agree on how to do that. I spoke with a contractor who lives down the street, and he told me that I need to remove my roof and put down rigid insulation. Another friend, who works as a handyman, told me I should have solid foam insulation blown into the rafter space (assuming there is no insulation there now). Yet another told me to get a ridge vent. Aaaaaargh! I'm so confused!


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## mics_54 (Sep 7, 2009)

Sorry for your loss and your difficulties.

You apparently have inaddiquate insulation and ventilation in the small space in the roof above your cathedral ceiling. As you probably know warm moist air can condensate upon relatively cooler surfaces under certain conditions. It's not easily predicted if you have sufficient space with a 2x6 rafter to get addiquate insulation to eliminate the dew point circumstances that create the condensate. Unfortunately there are no "cheap" fixes although some may be less costly than others.

Did you change the color of the roof when you had it re-shingled? Making the roof darker would probably cause the space to become warmer. This could have created the circumstances where the dew point was reached where it had not previously.

Unfortunately adding a little ventilation may actually make the problem worse in that it would keep the area supplied with more moisture layden air.


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## stuart45 (Jun 20, 2009)

When the air in the roof space is really hot in the day it will hold a lot of moisture. This will often come from the moisture produced in the house from every day living such as cooking, drying clothes or breathing. At night the roof will loose heat by radiation, especially to your clear blue Californian sky. As the temperature drops condensation is likely to happen in the space. Ventilation will help prevent this as long as the moisture content is lower in the outside air. In the UK condensation in the roof spaces has become a much bigger problem since people started using insulation between the joists in the 60's.


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## barbaraizac (Sep 20, 2009)

*condensation problem on cathedral ceiling*

The color of the new shingles are the same color as the old ones. The only thing that has changed is that there is now one layer of roofing instead of two. My biggest struggle is that no one can agree on what to do. 

I have a building contractor coming over tomorrow evening who was a good friend of my late husband. I really need to understand the structure of the roof better, and he will help me do that.


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## mics_54 (Sep 7, 2009)

I suppose its "possible" that two layers of shingles kept the roof/rafter space temperatures from reaching a dew point that one layer doesn't. It doesn't seem likely though. It sounds fishy that it wasn't wet before a new roofing job and now it is. 
I'm sure your contractor friend can figure it out. 

Interesting that the wet rafter space is directly above the skylight. That space probably doesnt have any air flow from the eaves to the ridge because the skylight blocks the space off.

You probably have a vapor barrier benieth the sheetrock on the ceiling. You contractor can check for one at openings like light fixtures (maybe) or in the attic access area.

It's a mystery.


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## stuart45 (Jun 20, 2009)

Vapour checks often get damaged when things like skylights are installed. I would be surprised if changing the roof covering had caused a condensation problem.


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## barbaraizac (Sep 20, 2009)

*Condensation Problem*

The skylight went in in 1991 and has never caused even the slightest condensation problem in all that time.


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## mics_54 (Sep 7, 2009)

> The skylight went in in 1991 and has never caused even the slightest condensation problem in all that time.


that you know of. The skylight is penetrating the roof...it cant penetrate the roof without blocking off airflow from the eave to the ridge. 

Not saying its causing condensation...but im not saying it isnt either. But if it were...you'd likely not know unless it was bad.


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## stuart45 (Jun 20, 2009)

Is it possible that you have had an exeptionally hot humid summer, with colder nighttime temperatures which could have altered the balance and caused the condensation. For one layer of shingles to make the difference, the surface temperatures of the roof elements must have been very close to the dew points in the original roof.


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## mics_54 (Sep 7, 2009)

....not to mention that a little condensation on sheetrock wouldnt be noticed...repeated condensation eventually saturates the sheetrock. Heat transfer characteristics of saturated drywall are different than dry sheetrock. The moisture causes it to transfer heat more readily and make the problem even worse. Insulation is probably also getting damp making it less effective. Over time the problem becomes noticable from a distance....mold begins to appear...paint flakes..it begins to smell.


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## barbaraizac (Sep 20, 2009)

The humidity is high here. I live less than a mile from the beach. 

So do you think that rigid insulation would help? I know I need to take care of the problem before I get mold, wood rot, termites, etc.

Meanwhile I'm pretty sure that the swine flu has me in its grips. Feels like I've been run over by a bus. Aaaaaargh!


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## mics_54 (Sep 7, 2009)

ridgid or sprayed foam would give you the greatest R value per inch. (around R7/in) All the issues have to be addressed/checked. Insulation, vapor inflitration, ventilation. Let us know what your contractor says!


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## barbaraizac (Sep 20, 2009)

Am down with the flu. Sick as a dog (PIG?), so I called the contractor and told him we'll have to reschedule his inspection. Bad timing to get sick!


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## stuart45 (Jun 20, 2009)

Get well soon barbaraizac.
As mics 54 said there are a number of issues to be checked which can only be done on site. When surveyors check a property for condensation they take the R/H and temperatures of inside the roof space, inside the property and outside. They also use a surface thermometer to take the temperatures of the building elements involved. A number of these readings are taken during the day and night. This can pinpoint when and where condensation is taking place.


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## AaronB (Jan 29, 2005)

Did the roofers replace any decking in the area above the skylight?


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## barbaraizac (Sep 20, 2009)

I'm almost positive that no decking was replaced with the re-roofing, but I'll ask him when I next speak with him.


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## AaronB (Jan 29, 2005)

Reason being... It sounds as if youre missing some insulation at that point. Are you running your air conditioner?


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## barbaraizac (Sep 20, 2009)

I've tried running my air conditioner, as well as leaving it off for several days. No impact on the ceiling sweat either way. Today we are supposed to have very hot, dry conditions. Humidity may fall under 10%. Will be interesting to see how that affects the problem. By late afternoon, I'll have no choice but to turn on the air conditioning, which will dry out the air even more.

Swine flu (no joke) still has me down for the count. Aaaaaargh!


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## AaronB (Jan 29, 2005)

Yeah, flus are nasty every year.


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## Ed the Roofer (Jan 27, 2007)

Go to page 6 of this brochure from Air Vent for your solution to the problem and the reasons why it is occurring.

http://www.airvent.com/pdf/literature/VentViews_HipRoofs.pdf

This previous thread also discusses, somewhat of a similar circumstance.

http://www.diychatroom.com/f9/how-properly-vent-hip-roof-21574/

Ed


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## barbaraizac (Sep 20, 2009)

Ed, thank you, thank you, thank you!:thumbup:


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## AaronB (Jan 29, 2005)

Is this a condensation issue on the interior or an attic condensation issue which is causing damage from the top of the ceiling drywall (attic side) to the bottom (living space side)?


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## barbaraizac (Sep 20, 2009)

Hi Aaron. The condensation is appearing on my cathedral ceiling. There is no attic space whatsoever. The drywall is attached directly to the 2x6" rafters.


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## AaronB (Jan 29, 2005)

In that case I really doubt venting that space would do any good under these conditions. 

Can you provide any pics of the condensation?


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## barbaraizac (Sep 20, 2009)

Aaron, I don't understand. Everything I've read has said that condensation on cathedral ceilings is caused by inadequate ventilation. If I don't try to vent the area between the sheathing and the drywall, then what other solution is there?


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## mics_54 (Sep 7, 2009)

inadiquate ventilation NEVER causes condensation...condensation is only cause by one thing...cooling of moisture laden air. You can remedy condensation with ventilation. The purpose of ventilation is removing warm air from the space.


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## Ed the Roofer (Jan 27, 2007)

barbaraizac said:


> Aaron, I don't understand. Everything I've read has said that condensation on cathedral ceilings is caused by inadequate ventilation. If I don't try to vent the area between the sheathing and the drywall, then what other solution is there?


Don't let them get picky on semantics.

Unobstructed Intake To Exhaust Airflow, known as Ventilation is what is needed to mitigate the condensation symptoms.

Cathedral/Vaulted ceilings pose additional difficulties in creating enough flowage and even the skylight rafter-bay bypass is very rudimentary at best, but at least provides a viable option to consider, while weighting the costs incurred versus the risk of not doing it and the problems that you now know will occur.

Ed


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## AaronB (Jan 29, 2005)

Ok, here's the scenario...

You have condensation on the INTERIOR of your home. The water vapor is condensing on ONE particular cold spot. Find out why this spot in particular is cold and remedy it.


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## mics_54 (Sep 7, 2009)

> Don't let them get picky on semantics.


There are no semantics involved in noting what condensation IS. The fact is that if warm moist air contacts a cold surface and reaches the dew point, it doesnt matter how much ventilation there is...you will get condensation. That's why there is a pan under evaparator coils.

The point is..as previously stated..that all the issues need to be addressed...not just ventilation. She needs some one to diagnose the problem on site. It's weird that it "just started" when she had the roof replaced.


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## AaronB (Jan 29, 2005)

If you had an entire ceiling with condensation on it, I would tell you to insulate and add exhaust ventilation to your conditioned space.

Since it is only on ONE SINGLE SPOT on your ceiling (not in the rafter bays on the underside of the roofdeck) then ventilating the roof isnt going to do you one damned bit of good.

Why arent all you "roofers" thinking of such things????


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## AaronB (Jan 29, 2005)

Ed the Roofer said:


> Don't let them get picky on semantics.
> 
> Unobstructed Intake To Exhaust Airflow, known as Ventilation is what is needed to mitigate the condensation symptoms.
> 
> ...


Ed, how does venting the rafter space relate to this situation???!!!???!!!???


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## barbaraizac (Sep 20, 2009)

No new decking was installed during the re-roofing. 

Although the new roof was installed last winter, I never saw any signs of condensation until it got hot this summer. The skylight was installed in 1991 and never caused any problems with condensation. As I wrote in my first post, the only thing that has changed is that I now have one layer of composition shingle, whereas before there were two layers. Perhaps the additional layer acted as an insulator and lowered the heat build-up between the decking and the drywall? The skylight flashing is in good shape, so it's not causing any problems. 

The problem undoubtedly exists under the entire section of roofing above my ceiling, and not just the area above the skylight. As described earlier, when I went up on the roof in the early morning, I found that ALL of the roofing above the cathedral ceiling was damp. The rest of my house has an attic space, and none of that roofing was damp at all. So even though I'm only seeing condensation above my skylight, where airflow is really restricted, I think the problem is occurring to a lesser extent throughout the entire ceiling.

I really am down with the swine flu. No joke. Once I'm no longer contagious, my contractor friend is going to come over and give me his assessment of the problem, along with what he thinks about the roofer's idea for resolution (which right now is to just drill holes under the eaves). I think a ridge vent will also be required, as well as holes drilled into the bays around the skylight as suggested by Ed.


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## mics_54 (Sep 7, 2009)

good plan..gws


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## AaronB (Jan 29, 2005)

How cold was it outside when you found that you had dew on your area above this ceiling? Was the air conditioner running? What was the relative humidity and barometric pressure? Does this occur even in winter? Are you getting interior condensation on the rest of the cathedral ceiling as well as above the skylight? What time of year was it when you checked the roof? Are you in a mountainous area? There IS a drywall ceiling, correct?


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## AaronB (Jan 29, 2005)

Is there condensation on the inside in the morning on days when the roof above this section is wet and the rest of the roof is not?


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## AaronB (Jan 29, 2005)

The reason I ask is IF you have a situation whereas the moisture is from vapor drive instead of condensation, then water vapor drives from hot to cold. This is why only true vapor barrier membranes (below 1.0 perm) will stop "leaks" on freezers.

I am trying to consider all possibilities, and pictures with time stamps and ambient temperature readings both inside and out with all of the above conditions noted would help a LOT.


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## barbaraizac (Sep 20, 2009)

I live in Southern California less than a mile from the ocean. The relative humidity is usually around 65%. I first noticed the condensation on the sloped ceiling above the skylight (approx 2x2' evenly distributed) about three months ago. No condensation appeared anywhere else in the room. I wasn't using the air conditioner at all then. The shower is tiny in the master bath, so I use another bathroom for showering. I find the condensation above the skylight every morning. By the end of the day, it's almost entirely dried out. This happens every day, whether I use the air conditioner or not. I sleep with the skylight and windows open every night.

I went up on the roof a week ago today. The roofer was there to install an O'Haven roof vent above the skylight (which failed to correct the problem). That's when we saw that the entire roof over the cathedral ceiling was damp. Interestingly enough, that section of roofing also covers the master bath, and the roof was dry above the bathroom area. The bathroom does NOT have a cathedral ceiling, so it has attic space above it. 

I did notice that there are holes drilled under the eaves over the bathroom area for ventilation, but there are no ventilation holes under the bedroom eaves (lower end of slope). 

Right now Southern California is experiencing extremely dry winds and air, so the drywall on my ceiling, while still getting damp, isn't looking nearly as wet as it usually does. I'm definitely feeling better today, so as soon as the sun comes up, I'll go up on the roof and see how wet it looks. I'm sorry to say that I don't have a digital camera, so I can't take any pics. Oh, and the roofer used a 30lbASTM felt underlayment. The slope is 3/12.


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## barbaraizac (Sep 20, 2009)

Forgot to answer the question about the outside temp the morning I discovered the damp roof. It was probably 65-68 degrees, as it is most of our summer mornings. Our highs are usually around 85 in the summer, and other than the last couple of weeks of scorching heat, we've had typical summer weather.


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## barbaraizac (Sep 20, 2009)

Just went up on roof and found that it's damp over the entire house. The marine layer is really heavy this morning. I checked the humidity, and it's 90%. The temp is 62 degrees. Yesterday's high was 92, and the humidity was down to 35%. Bizarre weather for us.


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## AaronB (Jan 29, 2005)

And no air conditioning nor heat is on, correct?


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## barbaraizac (Sep 20, 2009)

Correct; no heating or air conditioning is on.


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## roofboy (Jan 18, 2007)

Hello,

Another possibility is that with the products available today, your roof "tightened up",or it is not letting the roof breathe out through the felt and shingles. 
It is possible that even with two layers it still was able to breathe before.

Just a thought.

Keith


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## AaronB (Jan 29, 2005)

Go back to vacation, Steinke. J/K


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## AaronB (Jan 29, 2005)

The exterior dew is not associated with this situation except whereas it evaporates off the attic areas sooner than the cathedral area because it is generally warmer in the attic areas, advancing the evaporation.

Condensation in the attic or rafter areas is not so much associated with interior condensation, either.

It still sounds to me as if you are missing insulation at that area. Back when I allowed smoking on the roof, someone had dropped a burrning butt into the insulation, requiring us to remove the decking and remove n replace the insulation. This is just one scenario that I have witnessed. Smoking is no longer allowed on my roofs.

Check this area for insulation, and make sure that if it is there, it is ample.


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## barbaraizac (Sep 20, 2009)

Thanks for the insight as to why the entire roofing over the sloped ceiling was wet. That makes a lot of sense.

My late husband's good friend, who is a building contractor, is coming over Monday to check things out for me. I'll have him cut out a small piece of drywall above the skylight to check out the insulation. On Tuesday I'll be on a cruise ship to Cabo with 7 firefighter wives. Mexico will never be the same. :laughing:


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## AaronB (Jan 29, 2005)

I think it would be easier to check from the rooftop.


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## roofboy (Jan 18, 2007)

Hello,

Aaron, other than the humidity and the non paid vacation I would love to stay in Florida.



Keith


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