# Cathedral Ceiling Insulation Options



## Bret Hart (Jan 3, 2013)

Just wondering what would be the best option for adding to the R-value of a cathedral ceiling in a modular home or just improving it's performance. It is just under 2000 sq. ft. and appeared to be fairly well insulated and vented. I don't see any obvious openings from the inside for heat to escape at any kind of volume. When I put the new chimney through the ceiling, I could see what looked like at least 10" of fiberglass batts. so I'm guessing at around R-30. Ice dam build up is more than expected. 

It has 10 or 12 of these vents: http://www.lowes.com/pd_157025-52595-PRV61BL_0__?productId=3284536&Ntt=roof+vent near the ridge only they are 12"x12" and the eves are vented from end to end of the building.

I am hoping that my only option isn't removing all the drywall and starting over.


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## jharkin (Jan 3, 2013)

Im guessing the problem is not R value, but rather you have leaks letting conditioned air into the ceiling. Do you have any recessed lights in that area?

I had a similar situation, cathedral ceiling over kitchen with R-32 fibergalss _and_ vent space_ and_ a continuous ridge vent that still ice dammed. 

I found the problem was 4 old style non-airtight, non-IC can lights in that ceiling with 65watt floods that were leaking massive heat into the ceiling. I replaced them with airtight/IC cans, caulked them tight and replaced the 65w bulbs with 15w LEDs.  Ice damming solved.


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## Bret Hart (Jan 3, 2013)

There aren't any recessed lights anywhere in the home and the ice dam is the same from end to end on both the front and back of the house. Maybe I should remove the molding where the walls meet the ceiling and look for gaps there or just plan on caulking it all and replacing the molding. I do agree that there is excess heat getting up there somehow.

This is what the ice dam looked like before it warmed up a bit last weekend and I carefully removed it after the water got between the ice and shingles.


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## ScotO (Jan 3, 2013)

What kind of vapor barrier do you have in that ceiling?  I just installed two cathedral ceilings in my living room project, using tongue and groove pine, air-tite recessed light cans and a good heavy plastic vapor barrier.  The vapor barrier is taped at all seams and where staples were ripped through, etc., and sealed with hi-temp RTV around the can light openings.  I can tell you that the vapor barrier makes a HUGE difference.  I used a total of R43 in that ceiling, with both baffles at the eaves and a ridgevent at the peak.  I am leaking a miniscule amount of heat/vapor through some spots in the can lights, I plan on sealing those spots with high temp silicone......but I have NO ice damming issues whatsoever, the roof still has snow (no ice) on it and I've had the fire burning out there pretty much nonstop since Thanksgiving...


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## semipro (Jan 3, 2013)

Check out this article: http://www.finehomebuilding.com/how-to/articles/a-crash-course-in-roof-venting.aspx
Option 3 is is a "cold roof" where ventilation is removed and insulation is added above the sheathing. 
Further info on this can be found at www.buildingscience.com.


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## GaryGary (Jan 3, 2013)

Hi,
This is not a great solution, but it does work pretty well -- at least until you can work out something better.

Get a roof-rake and use it to pull the snow off the roof after snowstorms.
http://www.roofrake.com/   several outfits make them.

Its surprisingly fast to use and it definitely reduces ice dam problems.  Since you don't have the snow on the higher parts of the roof melting, running down, and then freezing at the edge of the roof to add to the dam.

Gary


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## Bret Hart (Jan 4, 2013)

Thanks for the tips.

Gary,
I was hoping to stay away from the roof rake because of the work involved. We get a lot of lake effect snow here and I'm thinking I might look like a body builder by spring. The "Warden" might like that though instead of my beer belly. 

Scott,
Now that you mentioned it, I don't remember seeing a vapor barrier up there when installing the chimney and cathedral box. Might have just missed it though because I didn't specifically look for it. If it's not there, I'll bet that's one of the biggest issues. I will find a way to get my mechanics scope up in there and have a look around.

By the way, awesome job on your hearth build.

Semipro,
Thanks for the links. I will be reading them thoroughly to see what I can do.


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## jharkin (Jan 4, 2013)

Even if you have no vapor barrier don't loose hope. I don't have one and have been able to eliminate a lot of the ice with careful sealing and blown in insulation retrofit. The only part of my roof that still gets any meltis the area over the section of storage attic. In this area I have the internal chimney for the stove, a bath ceiling that didn't get enough insulation and a leaky attic door. I'm working on insulating and sealing those now.

I'm no expert, but I think with some careful work you should be able to limit leakage enough to keep the ice manageable without gutting the attic. You might always have some but at least not enough to cause damage (assume the roof has ice and water shield).


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## 91LMS (Jan 4, 2013)

when i insulated my cathedral ceiling with r30 paper faced insulation i was told in no way to put a vapor barrier or foamular directly against the paper faced insulation or i would run into issues.  if any moisture were to develope it would be trapped and form mold.  not that it cant be done but an air gap needs to be established via strapping?  i get ice buildup around my chimney where i had to dead end the rafter mate vent so basically the roof has no way of staying cold there by drafting cold air from the soffit up to the ridge vent. 

 i may have made a poor choice selecting paper face insulation which painted me into that corner????


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## Bret Hart (Jan 4, 2013)

jharkin said:


> Even if you have no vapor barrier don't loose hope. I don't have one and have been able to eliminate a lot of the ice with careful sealing and blown in insulation retrofit. The only part of my roof that still gets any meltis the area over the section of storage attic. In this area I have the internal chimney for the stove, a bath ceiling that didn't get enough insulation and a leaky attic door. I'm working on insulating and sealing those now.
> 
> I'm no expert, but I think with some careful work you should be able to limit leakage enough to keep the ice manageable without gutting the attic. You might always have some but at least not enough to cause damage (assume the roof has ice and water shield).


 

That's the part that worries me. There isn't any attic space to speak of.
At the outside walls, there is about 6 or 8 inches from the top of the insulation to the bottom of the beams that hold the roof sheathing and at the ridge it looks like there is about 12 to 14 inches. No way to get in there without removing the drywall ceiling which would be a job I'm not interested in. Not sure if insulation could be blown in all the way to the ridge from the soffit openings as I've never done anything like that.


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## ScotO (Jan 4, 2013)

91LMS said:


> when i insulated my cathedral ceiling with r30 paper faced insulation i was told in no way to put a vapor barrier or foamular directly against the paper faced insulation or i would run into issues.  if any moisture were to develope it would be trapped and form mold.  not that it cant be done but an air gap needs to be established via strapping?  i get ice buildup around my chimney where i had to dead end the rafter mate vent so basically the roof has no way of staying cold there by drafting cold air from the soffit up to the ridge vent.
> 
> i may have made a poor choice selecting paper face insulation which painted me into that corner????


After extensive.research prior to my install, I chose unfaced insulation (R30 above the truss, R13 between them), and used the good, sealed, plastic vapor barrier for total coverage.  With paper faced insulation, you still get a lot of vapor loss (from what I read on it).  You are correct about NOT installing a plastic vapor barrier over a paper faced insulation.......the double vapor barrier will trap moisture and definitely lead to mold problems.  My ceiling is properly vented, baffled, and so far I'm impressed with the performance of it.  It really pays to research your options before committing on a procedure.  Every climate has pros and cons in regards to the different installation methods.


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## Bret Hart (Jan 4, 2013)

91LMS said:


> when i insulated my cathedral ceiling with r30 paper faced insulation i was told in no way to put a vapor barrier or foamular directly against the paper faced insulation or i would run into issues. if any moisture were to develope it would be trapped and form mold. not that it cant be done but an air gap needs to be established via strapping? i get ice buildup around my chimney where i had to dead end the rafter mate vent so basically the roof has no way of staying cold there by drafting cold air from the soffit up to the ridge vent.
> 
> i may have made a poor choice selecting paper face insulation which painted me into that corner????


 
Your post just made me remember that the insulation up there has the paper face so I guess there is a vapor barrier.

This isn't looking good.


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## ScotO (Jan 4, 2013)

Bret Hart said:


> Your post just made me remember that the insulation up there has the paper face so I guess there is a vapor barrier.
> 
> This isn't looking good.


like Jeremy said earlier, don't lose hope.  There might be another way around this.  

Worst case scenario, you MAY have to take the ceiling down (again, worst case scenario).  How big of a space are we talking about here?  Any recessed (can) lights in this ceiling?  Any other leaky places (trap doors, bathroom ceiling vent dans, etc.)?

Have you considered maybe installing heat tape along the eaves to help keep the ice from damming up?  That may possibly be an option (if all else fails and you do not want to tear that ceiling out).


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## Bret Hart (Jan 4, 2013)

Scotty Overkill said:


> like Jeremy said earlier, don't lose hope. There might be another way around this.
> 
> Worst case scenario, you MAY have to take the ceiling down (again, worst case scenario). How big of a space are we talking about here? Any recessed (can) lights in this ceiling? Any other leaky places (trap doors, bathroom ceiling vent dans, etc.)?
> 
> Have you considered maybe installing heat tape along the eaves to help keep the ice from damming up? That may possibly be an option (if all else fails and you do not want to tear that ceiling out).


 

There are 2 bath vents and nothing else is recessed. No trap doors either. I am thinking I should seal all the light fixtures, might have been done poorly when built, since this could add to the problem.

The space is fairly small in volume (see post #10) but it runs the entire length of the house which is around 70 or so feet.

The thing that gets me is, I would have thought the ice dam would be worse in the areas of the vent fans or the chimney with the extra localized heat. It isn't though. The ice dam is almost dead even the entire length of the roof on both the front and back side.

I have thought about the heat tape but spinning the electric meter faster isn't very appealing. Might have to do it though. Starting to think that a few feet of flashing up from the drip edge in the spring may be someplace to start.


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## woodgeek (Jan 4, 2013)

If the cath ceiling is drywalled completely, then there is no airflow, and the vapor diffusion through drywall+paint is NOT going to be a problem with a vented roof.  The ice damming IS telling you you have conditioned air flow (or an insulation gap) into the ceiling cavity, but it is not happening because of vapor diffusing through drywall (or lack of a 'vapor barrier').

More likely, there is an air path between the wall cavities and the ceiling, or not enough insulation right at the corner due to some detail of the framing.  The Worst case scenario is not a whole roof full of mold (the venting will prevent that), or a complete tearout of the entire ceiling.  The choice is either live with the ice dams (lots of folks do), rake or install a heat rope along your eaves. For a permanent and passive fix: tear into the corner (either the wall or the bottom of the ceiling) and seal the paths, or beef up the insulation with spray foam, and then re-drywall.  JEremy's suggestion of blowing some AIR retardant insulation into the wall cavities would help, if your walls needed that also.


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## Bret Hart (Jan 4, 2013)

woodgeek said:


> If the cath ceiling is drywalled completely, then there is no airflow, and the vapor diffusion through drywall+paint is NOT going to be a problem with a vented roof. The ice damming IS telling you you have conditioned air flow (or an insulation gap) into the ceiling cavity, but it is not happening because of vapor diffusing through drywall (or lack of a 'vapor barrier').
> 
> More likely, there is an air path between the wall cavities and the ceiling, or not enough insulation right at the corner due to some detail of the framing. The Worst case scenario is not a whole roof full of mold (the venting will prevent that), or a complete tearout of the entire ceiling. The choice is either live with the ice dams (lots of folks do), rake or install a heat rope along your eaves. For a permanent and passive fix: tear into the corner (either the wall or the bottom of the ceiling) and seal the paths, or beef up the insulation with spray foam, and then re-drywall. JEremy's suggestion of blowing some AIR retardant insulation into the wall cavities would help, if your walls needed that also.


 

Thanks woodgeek. This is a manufactured home, basically a mobile built in some factory and hauled here and set on the foundation with a crane. The walls are 2x6 and I've pulled a few switch plates to check how they were insulated. Cavity is full and the walls never feel cold. I will pull a few more pieces of the soffit cover down and check the insulation where the ceiling meets the walls. I think I'm going to check every inch of where the walls meet the ceiling inside with my laser thermometer tonight when the temp drops to see if I can find any cooler spots.

It looks as if they built the entire outer shell of the house, drywalled the ceiling, and then added the interior walls where they wanted them afterward. I don't think there is any leakage from the interior walls if you meant that as well? Just guessing here as I'm no pro at this which I'm sure you can tell.


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## semipro (Jan 4, 2013)

woodgeek said:


> The choice is either live with the ice dams (lots of folks do), rake or install a heat rope along your eaves.


...Or insulate above the existing roof as I pointed out earlier which is widely promoted by many experts such as those at BuidlingScience.com, a resource commonly referenced here. If you do this (correctly) you get:

Less overall conductive heat loss through the roof and prevention of ice damming
Less overall convective heat loss through the roof because venting is not required (and should be removed)
Prevention of moisture related issues in the existing roof structure because the dew point is moved to a point within the foam insulation added to the roof. So condensation of any moisture making its way into your ceiling does not form on:
the drywall,
within the fiberglass insulation,
at any vapor barrier already in the ceiling/roof
or on the underside of the roof sheathing.


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## woodgeek (Jan 4, 2013)

Bret Hart said:


> Thanks woodgeek. This is a manufactured home, basically a mobile built in some factory and hauled here and set on the foundation with a crane. The walls are 2x6 and I've pulled a few switch plates to check how they were insulated. Cavity is full and the walls never feel cold. I will pull a few more pieces of the soffit cover down and check the insulation where the ceiling meets the walls. I think I'm going to check every inch of where the walls meet the ceiling inside with my laser thermometer tonight when the temp drops to see if I can find any cooler spots.
> 
> It looks as if they built the entire outer shell of the house, drywalled the ceiling, and then added the interior walls where they wanted them afterward. I don't think there is any leakage from the interior walls if you meant that as well? Just guessing here as I'm no pro at this which I'm sure you can tell.


 
I'm no pro either.  Can the manufacturer send you a drawing of the wall/ceiling interface??  Do you have any 'unfinished' locations you can inspect to try to figure out if the ceiling cavity is airsealed near that point??


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## ScotO (Jan 4, 2013)

semipro said:


> ...Or insulate above the existing roof as I pointed out earlier which is widely promoted by many experts such as those at BuidlingScience.com, a resource commonly referenced here. If you do this (correctly) you get:
> 
> Less overall conductive heat loss through the roof and prevention of ice damming
> Less overall convective heat loss through the roof because venting is not required (and should be removed)
> ...


I read that link and that's an interesting method.......if that was to be used, maybe Bret could consider installing a metal roof as well (which would further help out with getting rid of the ice dams).


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## semipro (Jan 4, 2013)

Scotty Overkill said:


> I read that link and that's an interesting method.......if that was to be used, maybe Bret could consider installing a metal roof as well (which would further help out with getting rid of the ice dams).


Which is exactly what I plan to do.
I followed  your insulation project Scotty and wished I could have done something similar. 
Unfortunately, I'm stuck in a situation where all the drywall (and plaster veneer) is already up and the roof structure is complex because of a mix of cathedral and non-cathedral type ceilings with some weird attic spaces.


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## Bret Hart (Jan 4, 2013)

semipro said:


> ...Or insulate above the existing roof as I pointed out earlier which is widely promoted by many experts such as those at BuidlingScience.com, a resource commonly referenced here. If you do this (correctly) you get:
> 
> Less overall conductive heat loss through the roof and prevention of ice damming
> Less overall convective heat loss through the roof because venting is not required (and should be removed)
> ...


 
Still reading through all of that info. Damn, that's a lot to take in but the pros know what they are doing.

I had hoped to have a few more years left in that roof but after all of this, maybe it's time to move that up on the list. Option 3 looks good to me provided I can afford it.


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## ScotO (Jan 4, 2013)

semipro said:


> Which is exactly what I plan to do.
> I followed  your insulation project Scotty and wished I could have done something similar.
> Unfortunately, I'm stuck in a situation where all the drywall (and plaster veneer) is already up and the roof structure is complex because of a mix of cathedral and non-cathedral type ceilings with some weird attic spaces.



That sounds like a great plan, keep me posted on your install.  Down the road, I will be installing a metal roof.  I'll definitely be considering insulating the sheathing when I go to do that roof......


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## nate379 (Jan 4, 2013)

Well I had put a post but its gone now?

Metal roof would help out.


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## semipro (Jan 4, 2013)

Bret Hart said:


> Option 3 looks good to me provided I can afford it.


Actually, now that I look back at the PDF at that link what you'd really have would be what is shown as "Option 2" on page 71.  This is where the roof is converted from vented to non-vented and the existing fiberglass insulation is used in combination with foam board installed above the existing sheathing to create a "cold roof".


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## ihookem (Jan 5, 2013)

If you can get into an attic and see how it was insulated it will tell ya a bunch. Also, do you have much ice damming where there is no cathederal ceiling? I did notice with all the snow on the roof it takes little heat loss to make ice cicles. I had -9 and -4 here last week and there is no frost in the ground. That stuff insulates a lot. I don't get any ice cicles but I have energy heel trusses, closed off and sprayed with foam 4' up the bottom of the sheathing to not get ice. If you are getting ice where there is flat ceiling this is what I have done a few times to fix ice damming. I take 1" foam between the trusses. Keep foam 1" from the roof sheathing. This will make an air vent. Close off with foam between the top of wall and bottom of foam above the outside of the wall where the wall sheathing is. Foam doesn't have a dew point after 1" Make the foam go up between the trusses till ya get well above the insulation. I've done this before and it has worked. You may need more insulation and more venting to get the warm air out of the attic. I hope it wasn't confusing. By the way, my mom gre up in Utica.


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## Circus (Jan 30, 2013)

I just skimmed over the responsives and maybe someone commented already. I didn't see any ice dams in your pictures. At least anything caused by escaping heat.
When the air temperature is near freezing and you have two feet of snow insulating the roof there's going to be a little melting no matter how well insulated. The question is how often. Once every five years or once a day. Rot needs a lot of soakings.
Vapor barrior faults cause water stains on your ceiling.


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## Bret Chase (Jan 30, 2013)

91LMS said:


> when i insulated my cathedral ceiling with r30 paper faced insulation i was told in no way to put a vapor barrier or foamular directly against the paper faced insulation or i would run into issues. if any moisture were to develope it would be trapped and form mold. not that it cant be done but an air gap needs to be established via strapping? i get ice buildup around my chimney where i had to dead end the rafter mate vent so basically the roof has no way of staying cold there by drafting cold air from the soffit up to the ridge vent.
> 
> i may have made a poor choice selecting paper face insulation which painted me into that corner????


 
I don't use kraft paper faced insulation..... ever... There can only be a single vapor barrier in the whole system...  otherwise you run into moisture problems...


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## Bret Chase (Jan 30, 2013)

Bret Hart said:


> Thanks woodgeek. This is a manufactured home, basically a mobile built in some factory and hauled here and set on the foundation with a crane. The walls are 2x6 and I've pulled a few switch plates to check how they were insulated. Cavity is full and the walls never feel cold. I will pull a few more pieces of the soffit cover down and check the insulation where the ceiling meets the walls. I think I'm going to check every inch of where the walls meet the ceiling inside with my laser thermometer tonight when the temp drops to see if I can find any cooler spots.
> 
> It looks as if they built the entire outer shell of the house, drywalled the ceiling, and then added the interior walls where they wanted them afterward. I don't think there is any leakage from the interior walls if you meant that as well? Just guessing here as I'm no pro at this which I'm sure you can tell.


 
Ugh... modular housing... my brother has a modular, brand new in 2005... my house was built in 1865... he spent more than I did to heat his house with LPG than I did with K1....   K1 far more expensive than LPG (especially since he is getting the Selkirk rate....) and my house had NO insulation!. figure that one out...

BH, building a house as you've described is excellent from a fire prevention point of view... not always great from a energy savings point of view... pay close attention to where the modules were joined.... that is where you will lose the most heat.


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## 91LMS (Jan 31, 2013)

Bret Chase said:


> I don't use kraft paper faced insulation..... ever... There can only be a single vapor barrier in the whole system... otherwise you run into moisture problems...


 
with only having insulation and whichever material is chosen to finish, whether it be sheetrock, t&g, etc., are you saying paper faces is still a bad choice then?


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## Circus (Jan 31, 2013)

Bret Chase said:


> I don't use kraft paper faced insulation..... ever... There can only be a single vapor barrier in the whole system... otherwise you run into moisture problems...​


 You can lay a plastic barrior on the kraft paper side (interior) of kraft paper insulation. That still would only be one vapor barrior. Without all the holes.


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## Bret Hart (Jan 31, 2013)

Circus said:


> I just skimmed over the responsives and maybe someone commented already. I didn't see any ice dams in your pictures. At least anything caused by escaping heat.
> When the air temperature is near freezing and you have two feet of snow insulating the roof there's going to be a little melting no matter how well insulated. The question is how often. Once every five years or once a day. Rot needs a lot of soakings.
> Vapor barrior faults cause water stains on your ceiling.


 
No stains on the ceilings and thanks for pointing out the normal melting issues.





Bret Chase said:


> Ugh... modular housing... my brother has a modular, brand new in 2005... my house was built in 1865... he spent more than I did to heat his house with LPG than I did with K1.... K1 far more expensive than LPG (especially since he is getting the Selkirk rate....) and my house had NO insulation!. figure that one out...
> 
> BH, building a house as you've described is excellent from a fire prevention point of view... not always great from a energy savings point of view... pay close attention to where the modules were joined.... that is where you will lose the most heat.


 

Thanks BC. I spent some time with the IR temp gun and noticed that there was a bit of difference at the center of the house where they are joined. Going to pull the molding down and seal things up some when I get through the overload of work in the shop. Just been trying not to look at the ice since this is my busiest time of year.


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## Bret Chase (Jan 31, 2013)

91LMS said:


> with only having insulation and whichever material is chosen to finish, whether it be sheetrock, t&g, etc., are you saying paper faces is still a bad choice then?


 
Using unfaced batts and covering the walls with sheets of 6 mil poly with TAPED seams is far, far better as a vapor barrier than kraft paper is. paper is far too easily damaged and detriorates fairly quickly within the wall space..


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## Bret Chase (Jan 31, 2013)

Circus said:


> You can lay a plastic barrior on the kraft paper side (interior) of kraft paper insulation. That still would only be one vapor barrior. Without all the holes.


 
in that case, you'd be better served pulling the faces off the batt.... otherwise you're going to end up with water trapped between the poly and the paper...


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## woodgeek (Jan 31, 2013)

Just to be precise.....kraft paper is a lousy air barrier and vapor barrier (air and vapor both go around the paper). Properly detailed poly is a great air barrier and vapor barrier....but in most lower 48 climate zones a vapor barrier is not required (or can be bad) if a proper air barrier is in place. Intact drywall, with sealing of penetrations and framing gaps can be an effective air barrier while maintaining a small amount of (beneficial) drying capacity.

Torn/perforated kraft paper FG behind drywall is harmless, so long as there is no conditioned (humid) air moving in the cavity.

Poly is ok/recommended in Canada and (more or less) the US states on the canadian border.


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## Bret Chase (Jan 31, 2013)

a vapor barrier is most definitely required by code and is the standard practice in the state of Maine.... whether it was done properly or not... is an entirely different story...


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## woodgeek (Jan 31, 2013)

And one of these days....it will be dropped from the code.


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## Bret Chase (Jan 31, 2013)

I don't see that happening... with the MUBEC... the push is towards buildings so tight that w/o makeup air... the occupants would die in a day or two...


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## woodgeek (Feb 1, 2013)

And when they are airsealed (at the drywall, housewrap, etc), there is no need whatsoever for poly.


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## Circus (Feb 1, 2013)

woodgeek said:


> in most lower 48 climate zones a vapor barrier is not required (or can be bad) if a proper air barrier is in place.​


 
Wrong. Without a vapor barrior water condenses on the cold inner surface of the exterior wall and the cold exterior surface of the insulation. Shortly the insulation becomes soaked, the rafters drip water onto the ceiling and your building rots.


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## Ehouse (Feb 1, 2013)

I've used a vapor barrier primer in bathrooms instead of poly.


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## semipro (Feb 1, 2013)

woodgeek said:


> And when they are airsealed (at the drywall, housewrap, etc), there is no need whatsoever for poly





Circus said:


> Wrong. Without a vapor barrior water condenses on the cold inner surface of the exterior wall and the cold exterior surface of the insulation. Shortly the insulation becomes soaked, the rafters drip water onto the ceiling and your building rots.


This is actually fairly controversial. Conventional knowledge may be outdated.
These are really good articles on the subject which I strongly recommend those here read
http://www.greenbuildingadvisor.com/blogs/dept/musings/do-i-need-vapor-retarder.
http://www.greenbuildingadvisor.com/blogs/dept/musings/vapor-retarders-and-vapor-barriers


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## begreen (Feb 1, 2013)

Circus said:


> Wrong. Without a vapor barrior water condenses on the cold inner surface of the exterior wall and the cold exterior surface of the insulation. Shortly the insulation becomes soaked, the rafters drip water onto the ceiling and your building rots.


 
FWIW, our house is 88 yrs old. It has no vapor barrier and no house wrap. It was insulated about 16 yrs ago by a previous owner. When we did the remodel in 2006 a few walls were opened to make way for window or partition changes. Rodent damage we found in one area, but rot or moisture, no.


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## woodgeek (Feb 1, 2013)

Controversial is a good way to describe it. Semi's links are good, I also like:

http://www.energyvanguard.com/blog-...54110/You-Don-t-Need-a-Vapor-Barrier-Probably

Moisture problems are due to the leakage of conditioned air, not diffusion through sheet goods. A wall that has air leakage through the cavity and a vapor barrier between the interior and the cavity is still wet (due to the air leak) and can't dry (b/c of the poly).

Scotty did the right thing putting poly in his ceiling b/c he was using T&G boards, he needed something as an air barrier (tyvek would have been good) but poly was ok since the roof was vented above the insulation....it could dry upwards.


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## Bret Chase (Feb 1, 2013)

begreen said:


> FWIW, our house is 88 yrs old. It has no vapor barrier and no house wrap. It was insulated about 16 yrs ago by a previous owner. When we did the remodel in 2006 a few walls were opened to make way for window or partition changes. Rodent damage we found in one area, but rot or moisture, no.


 
that's because your house most likely leaks air like a sieve... just like my almost 150 year old house does... all that air leakage carries the water away with it...


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## begreen (Feb 2, 2013)

Exactly, there are no absolutes.


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## RustyShackleford (Feb 28, 2013)

jharkin said:


> Im guessing the problem is not R value, but rather you have leaks ...


I'd guess the same. If it's a cathedral ceiling, you're not gonna get that much better than R30, maybe R38 (and you'd have to add bafflles). A little arithmetic will show you that's not worth much.

Your btus/hour per degree-fahreinheit for your 2000 sqft ceiling will go from 2000/30 to 2000/38, reducing that number by about 14. So over the course of a 5000 degree-day winter (typical for your area ?), you will save about 1.7 million btus or 500 kilowatt hours. Using electric resistance heat and a typical 10 cents per kwh rate, you'd save $50 a year (in heating). Use a heat pump or natural gas (or A/C, which is also a heat pump) and it's way less savings.

Of course there's also the issue of comfort (as was pointed out to me when I posted a similar calculation while wondering aloud whether to go with more expensive window glass), but as others have pointed out, air leakage has a vastly more important effect on comfort.


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## welderboyjk (Mar 4, 2013)

I've got a question for the original poster, with all of the snow that I can see in the two roof pics you posted I'm guessing that your vents near the peak of the roof were covered, correct?
Absolutely NO insulation is perfect, the purpose of venting is to let the heat that does wander through the insulation out. If they were covered I can see why you had some ice. BTW it didn't look that bad to me either.


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## Bret Hart (Mar 14, 2013)

welderboyjk said:


> I've got a question for the original poster, with all of the snow that I can see in the two roof pics you posted I'm guessing that your vents near the peak of the roof were covered, correct?
> Absolutely NO insulation is perfect, the purpose of venting is to let the heat that does wander through the insulation out. If they were covered I can see why you had some ice. BTW it didn't look that bad to me either.


 

Just noticed that I missed this post. The vents were definitely covered after that snow in the pics but much of the 3 inch thick ice at the edge of the roof was there prior to that deep snow. The vents had been clear and working.

Thanks for all the help and for the reassurance that maybe it's not too bad after all.


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