roof insulation ...

[Greg Cuetara]

Question for you house builders out there. What do you typically use for wall and roof insulation? I have 2x6 walls and think I have r-19 in the walls with 1" rigid foam insulation on the inside of the studs. I have a sloped ceiling which is open for 2 stories. It is 2x10 construction. The house is 30 years old. The original builder used chicken wire to hold the insulation back a few inches from the roof sheathing. It sounds and looks like it works well.

I have no idea exactly how much insulation is up in the roof. The house is also pretty tight and seems to be well insulated.

Now the reason I am asking...I have a leak in my roof and had an 'Engineer' come into the house and say that I should have r-38 in the ceiling which I probably don't have. He is saying that the leak is caused by lack of proper ventilation and insulation in the roof. There is a bit more to it all and really hard for anyone to judge the problem.

What I am really looking for is how much insulation I should have in my ceiling?

Thanks,
Greg

[Brian Effinger]

Greg, in a 2x10 cathedral ceiling, the most you can get is R-30, and that is if you buy the batts specifically made for these types of ceilings. Otherwise it is an R-26 (2 layers of R-13 which add up to 26 and 7" in depth).

I am not sure how proper insulation and ventilation can cause a leak though. It is true that you do need both, especially ventilation. It helps with the heating of the house as well as moisture. Also there should be some sort of vent down at the bottom of the roof, and a vent up high, like a ridge vent.

I have a few questions though, so I can try to offer my 2 cents. What is the pitch of the roof? How old is the roof? And, does the roof butt up to any walls?
A low pitch roof is always worse than one with a high pitch (water & ice / snow don't flow off as well), and the age may indicate the construction methods, not to mention the fact that old roofs are ticking time bombs. As for the adjacent walls, if the roof was not flashed properly into it, it can leak.

As for my qualifications (if you can call it that :D) I'm an architect.

Brian

[Greg Cuetara]

Brian,
Let me see if I can answer your questions. At the soffit I have 4" dia. round vents in each 16" bay to let the air in. Not 100% ideal but they seem to do the job well right now. I think there is a ridge vent at the top.

The roof is a 7:12 pitch which I think is more steep than flat. The roof is about 10 years old but I don't think they used ice and water shield etc. Yes the roof does butt up against a wall which is where I think the leak is. I don't think the roofer flashed things properly or used ice and water shield...after a few hard winters with some ice build up and there is a leak. The 'Engineer' is saying that the roof is not insulated correctly, there is not enough air flow and that has caused the leak.

What would you use for insulation in a cathedral ceiling now? What would have been used 30 years ago?

Not sure if this makes a difference but the relative humidity outside was 35% and inside was 42%...from the 'Engineer's' calculations. He is saying that this 'Large' difference is causing condensation on the vapor barrier.

Thanks,
Greg

[Brian Effinger]

A 4"dia vent every 16" is good. It probably has as much (if not more) open area than the vented vinyl soffit used today. As long as the air is sucked in there, and has a free path up to the ridge, then the ventilation should be fine. You said the original builder used a wire mesh to keep the insulation off of the roof sheathing, so you should be ok. When I detail a house, I'll show a 1" airspace between the insulation and the underside of the sheathing. The 7:12 pitch is good too - not really steep, but not flat either. Not having ice & water shield is a bit of a bummer though. I believe it is required by code now, 2 feet back up the roof from the inside face of the wall.
With out standing in your yard and looking at your house, my bet would be on the wall / roof transition. There is probably a problem with the flashing and water & ice are getting in there.
Another question though that relates to ventilation. In the winter does the snow sit on the roof, or does it melt and drip down to the overhang and create icicles? If it does that, then the ventilation may not be properly done. And that could create havoc at the wall / roof transition as well.
I've attached a pdf detail of a recent addition that may be helpful.

[Brian Effinger]

I just saw the last sentence you added Greg. In this case the vapor barrier is the underside of the roof sheathing, so when the moisture from inside of the house migrates up into the roof assembly, if it is not properly ventilated it will condese on the plywood and build up until it leaks. If there is a ventilation space, then the moisture is sucked up the roof and out of the ridge vent.

[Greg Cuetara]

Brian,
Regarding the snow. I have lived in the house for 5 full winters. For the first 3 winters we did not have any problems and the snow was normal and not too much ice. A few icicles would form but typical for the climate up here in Maine. The past 2 winters have wreached havoc on my house. Last year we had snow...then it would get warm and melt a little bit and then drop down to negative temps overnight and freeze then it would rain and freeze and snow and warm up and get cold....etc. etc. This year has not been as bad with the ice but we did get some of the same as last winter, we also did get some build up in the gutters....it would warm up during the day and melt into the gutter and then freeze overnight. I am not positive the gutters have enough slope to them but they do drain well during rain storms during the summer time. Snow has gotten stuck in the gutters and I think backed things up a little bit.

About the vapor barrier. I am pretty sure there is a vapor barrier right on the inside of the drywall. Not quite sure if this is a good thing or a bad thing. I have heard conflicting things about vapor barriers.

Also, the detail you posted looks almost exactly like my wall / roof construction. Except for the ice and water shield that is.

I think you hit the nail on the head and hope that there is just a leak somewhere. Probably have to tear the roof apart to find the leak and fix the flashing.

Greg

[Brian Effinger]

Greg,
We've had the same kind of unusual winter here too. It has been really cold, and then we'd get a few days of above normal warmth. The constant thaw & then freezing is not good for typical residential construction - whether it was built properly or not. That could be a contributing factor too.

I hope you don't have a vapor barrier under the ceiling drywall. The vapor barrier should be on the wall, not the ceiling. The way your house was constructed, you want the moisture to go up into the ceiling cavity and escape through the ridge vent. As for the leak, if it is in the flashing at the wall, then it could be anywhere along the wall. Water has a bad habit of traveling some distance before showing itself.
If you have some time tomorrow, I wouldn't mind seeing a picture of the outside of the house. It may help to diagnose things. Also, an interior picture, in the room with the leak would probably help also. Might have a eureka moment looking at them.

Brian

[Greg Cuetara]

Brian,

Here is a picture of the roof / wall transition.

115003

As you can see there was some ice build up. This picture was taken right after we started getting a leak in the house. Most of the time there is no ice or snow right up against the wall.

At the interior there is a heavy timber beam with 4 - 2x6 studs as a support and all of the studs were rotted out. I don't think this could have happened with just condensation....even over 30 years.

Thanks for looking.
Greg

[Jim Kountz]

Could have been improperly flashed against the side too that could cause your leak. Whenever I have a wall that meets a roof surface like that I start with some 24" flashing bent in half. Then I roll out my felt up and over this followed by ice shield. Then when the shingles go on, step flashing is an absolute must. Siding should come down close but not touch the finished roofing surface unless its vinyl then it doesnt matter much. Im my neck of the woods ice shield is not a requirement just yet but I use the stuff freely on everything I build.

[Bob Lloyd]

Greg


I do not think the leak is cause by lack of insulation or ventilation, there are many homes with the same situation as yours that do not leak, except they would have rafter vents instead of the chicken wire. If you have a ridge vent then it appears that you have adequate ventilation. The insulation may not meet current code but it was probably fine when it was installed. If it is held "a few inches from the roof sheathing" you could use some more but as Brian said, you cannot get more than R-30 with fiberglass in that situation even if use use high density batts. The rot you have suggests that it has been leaking for a while and just now is showing itself. Different winters cause different effects. The leak appears to be in the area where the roof abuts the wall which suggests the flashing. If it was me I would fix the situation on the outside of the house by removing the roof shingles and flashing adjacent to the second story wall; you would also have to remove some walls shingles to do a good job. Laying ice barrier on the roof and up the wall should prevent the problem.

[David G Baker]

Brian,
My old farm house has several add on rooms and there are several areas that have leaked in the area that you are showing in your photo. When I had a new roof put on the roofer ran ice shield up the wall at every area where a new room was added. He also put two passes of ice shield on every overhang and at the peaks with the exception of the sides where he only used one pass. He put flashing up underneath the vinyl siding and used a lot of roofers caulk to hold them in place. No leaks since the new roof was installed.
I still have some ice dams on the lower edges of the roof but that is due to poor wall insulation and heat loss. The wall insulation is my next big project.

[Jim Becker]

I'm not so sure about the "leak" being caused by inadequate insulation, but yes, the current "standards" for roof insulation are in the R-38 range in most places. With 2x10, closed cell spray foam might be a good choice so you can get that R-value without adding wood to the rafters for the extra depth needed. We're at about R50 in our addition (contractor over-shot) and didn't use the entire depth of the 2x12 rafters and we did use baffles as required by our township. The closed cell foam also adds structural rigidity which should reduce flex and the lessen nail-pops, etc., with your roofing material.

On that roof-wall transition, ice/water membrane off the deck and up the wall about a foot will help tremendously to reduce the chance of a leak at that point. We have a similar, but actually more complex situation where the roof lines of the addition and original home/walls come together and the membrane was just one part of the solution to keep things dry over time.

[Lee Schierer]

Your "leak" was probably due to an ice dam on the lower portion of the roof. Even though your rafter bays may provide for air flow with the 4" hole at the bottom and ridge vent at the top, all of that air flow stops once you get a heavy layer of snow and/or ice over the ridge vent. What happens when the air flow stops is heat that leaks through the insulation, (yes even R-32 leaks heat) melts snow on the roof. The water runs down hill until it reaches the lower portion of the roof over the eves where the temperature is at freezing and the water freezes. Over time this ice layer gets bigger and bigger until water backs up higher than a course of shingles. At that point the water gets through the roofing and drips into the house.

The only cure is to have ice and water shield material installed under the roofing for 3-6' up from the edge of the roof before the shingles are installed and to keep the air moving. Even ice and water shield won't always prevent ice dams if the area under the shingles gets warmer than outside temps.

I had the same problem on my roof when it was reroofed 3 years ago without changing the insulation in the attic. They switched from peak vents to a ridge vent and the first time in 25+ years of owning the house we had ice build up on the roof whenever the snow got more than an inch or two over the ridge vent. I have reopened the peak vents so we will see next year if the problem reappears.

[Ken Higginbotham]

I used to work for a roofing company and have seen condensation so bad in an attic that it dripped on the ceiling sheetrock and looked like a leaky roof. The reason, in this case was because the owner had put plastic over the gable end vents. The tell-tell test for this is to examine the roofing nails that go through the decking that you can see from in the attic. If there are dark mildew looking stains around them then you have a condensation issue as the condensation will occur around the cooler nails first.

[Brian Effinger]

Brian,

Here is a picture of the roof / wall transition.

115003

As you can see there was some ice build up. This picture was taken right after we started getting a leak in the house. Most of the time there is no ice or snow right up against the wall.

At the interior there is a heavy timber beam with 4 - 2x6 studs as a support and all of the studs were rotted out. I don't think this could have happened with just condensation....even over 30 years.

Thanks for looking.
Greg

Greg, you'd be surprised how much condensation can build up in an attic, but I'd still suspect that it was a leak because of improper flashing. Just to throw a wrench into things, there is also a slight possibility that the roof 2 feet above the other one is the culprit. Again, it would be flashing against the wall there, but as I said it is only a slight possibility.

Even though it is only 10 years old, you may want to think about having a new roof installed in that area by a good contractor. Make sure there is ice and water shield used and that the proper flashing is used up against the wall. You said those supporting studs are rotted out, so you'll have some interior work as well. Now may be the time to update the insulation in the ceiling cavities with an R-30 (Owens Corning - the pink one - makes it). These 2 things don't necessarily have to be done together. Since this is quite an expense, you could do the roof soon and then follow up with the insulation a year or two down the road. Of course you should repair the 2x6 studs right away.


Could have been improperly flashed against the side too that could cause your leak. Whenever I have a wall that meets a roof surface like that I start with some 24" flashing bent in half. Then I roll out my felt up and over this followed by ice shield. Then when the shingles go on, step flashing is an absolute must. Siding should come down close but not touch the finished roofing surface unless its vinyl then it doesnt matter much. Im my neck of the woods ice shield is not a requirement just yet but I use the stuff freely on everything I build.

That ice & water shield is great stuff, isn't it? It seals up around the penetrating nails, and adheres to the roof. I am a firm believer in using it. It is especially useful on low pitched roofs. Just ice & water shield the whole thing.


I'm not so sure about the "leak" being caused by inadequate insulation, but yes, the current "standards" for roof insulation are in the R-38 range in most places. With 2x10, closed cell spray foam might be a good choice so you can get that R-value without adding wood to the rafters for the extra depth needed. We're at about R50 in our addition (contractor over-shot) and didn't use the entire depth of the 2x12 rafters and we did use baffles as required by our township. The closed cell foam also adds structural rigidity which should reduce flex and the lessen nail-pops, etc., with your roofing material.

I think that spray insulation is the way of the future. I just hope prices will come down as more people use it. With the closed cell variety, you don't even need ventilation in the attic spaces, you just need to have the attic conditioned. The foam acts as a vapor barrier and the HVAC system will take the moisture away. It is the same theory behind sips.

[David G Baker]

My roof had to be replaced due to lack of ventilation. The previous roofer did not open up the soffits, left insulation jammed tight against the soffits and caused the 1"X8" along with the 1/2" OSB to rot. I had to have all of the OSB and the 1"X8"s replaced. The 1x8s were soggy and black, the OSB that was 1/2 inch was swollen to approximately 3/4 inch thick in many places. The porch roof felt like sponge when walked on and the add on bedroom was the same as the porch roof. Cost me $14,000 to have the work done. The roof that was replaced was only 5 years old. Most of the damage was due to lack of ventilation and some was caused by water leaks. It is amazing how much moisture can accumulate in an attic that is not properly vented.

[Greg Cuetara]

Thanks for all the thoughts.

I really think my problem is due to a bad roofing job or improper flashing etc. We have a pretty tight house so I think things are working well but who really knows what is happening behind a wall without taking it down. I am pretty sure they did not use ice and water shield so I am thinking that would be the best place to start.

Greg

[Fred LeBail]

Greg,


I hope you don't have a vapor barrier under the ceiling drywall. The vapor barrier should be on the wall, not the ceiling. The way your house was constructed, you want the moisture to go up into the ceiling cavity and escape through the ridge vent.
Brian

I know we are a little farther north but we use vapor barrier under the ceiling drywall. In any moisture problems that I have had I was told be "the experts" was that there must be a problem with the vapor barrier and the escaping moisture is condensing in the cold attic air. Attic temp should be only 1 deg higher than the outside temp.