Cathedral Ceiling Insulation

[upsnake]

What about the door though? I am assuming that I would have to move the door over towards the center of the room to get the height clearance, that or the ceiling steps down after the door, but it seems like that would look odd. haha...

 

[GeeVee]

Yep! Been There; Done That... Sister 1x2 or 1 x 1 1/2 to each 2x6 so you have space between each one. Staple 1/4" lauan to the 1x2's to create an air space and spray foam over the lauan or use the egg crate between each. After you kill the mold.
Your roof needs to breath..

+1...

I use a 1x2 on each side of the rafter, pushed up against the bottom of the roof sheathing, and THERMOPLY- shiny side up against the 1x2 to create the vent gap from wall/eave to the peak/ridge vent, then insulate with fiberglass batts. You could get an R-30 (9.5") in that space left over when using the THERMOPLY as a radiant barrier and only putting a .5 x.5 spacer up. A half inch air gap is enough, the THERMOPLY will do well for you, and 9.5 inches of insulation only last about a year before settling to about 7 inches. All fiberglass insualtion shrinks a bit with gravity.

The air gap is important, but so is closing the end over the wall vertically, and the peak/ridge. Cold air is venting in- in the wintertime, let it flow without getting to your insulation

In the summer, heat conducting through the shingles is heating up your sheathing, and radiating heat into the insulation. The THERMOPLY will reflect this heat and send the hot air through the ridge vent, saving R-Value in the insulation and house. Radiant heat elimination in the summer is going to be a big energy saving, the THERMOPLY will also cut way down on your cold air sucikng heat out of the your heated space.

I see a lot of foam down here being used, and i might consider it for walls, but never my ceilings. You get a roof leak with foam in your ceilings, good luck finding it, and by then, the mold will be un fixable.

THERMOPLY is a great product. Light, easy to work with, inexpensive. Structural sub siding was its intended use, all out of an 1/8 piece of what feels like cardboard....

 

[mga]

What about the door though? I am assuming that I would have to move the door over towards the center of the room to get the height clearance, that or the ceiling steps down after the door, but it seems like that would look odd. haha...

yep.

i was going to suggest the same as aokpops....sister the joists, but then i saw the door pic.

cathedral ceilings are nice, but they must be designed properly when the house is being built. i've seen a few disasters when people decided to make a cathedral ceiling out of a regular ceiling and thought insulating it would work.

better give that project some serious thought or you'll end up back to square one in a couple of years.

 

[dave_dj1]

Your only talking about the unfinished side correct? If this is the case, do what you said initially. Install continuous prop a vent, put in some R 19 batts or high density R 23, then put 1" high R Thermax sheet over the rafters. This would give you an approximate R value of batts (R23 if you use high density) and R 6.5 for the one inch Thermax for a total of R 29.5.
You could put a 5/4" board in the angle portion of the door jamb, cut the door down approx. 1". I think this would be the most economical way out for you. Door would still look ok and would allow for the proper insulation in the unfinished side.
Most likely cause of the mold is an un vented attic, like I said before, check to see that the ridge is in fact vented. I've seen builders "forget" to cut the sheathing and/or the roof underlayment back to allow it to vent.
I'm a builder and have been for 33 years. If you have any other questions feel free to message me or ask here.

 

[upsnake]

Geevee -

Is this somewhat accurate to what you were describing?
Getting R30 in there would be great if i could.

I think the key thing more so than the value of the insulation is that i get the soffit and ridge vent correct.

Once again thanks for all your help everybody.

 

[elmoleaf]

Lots of advice and lots of opinions, I think you better have someone actually go there and look at it and offer an onsite opinion. I've built house for over 25 years and have built a few hundred in Michigan too. We got sued on one in Michigan and ended up paying over $100 g's just to make it go away. That particular house was a close design to your pictures, mold was the issue, homeowners was the problem. The pictures help but you really need someone to look at the whole thing to make sure it is done correctly. I like the idea of sprayfoam but I also like the idea of proper ventilation so I would think if you could put continous vents in the rafter space from the lower birds mouth to actual working ridge vent the foam would be the way to go. I see that adding to the rafter width isn't an easy fix so again the foam is out ahead again.

+1 on this. Not sure of building code requirements in your location, but 2009 IRBC requires R38 or R49 in the coldest climate zones.
There are also important details like those recessed lights. Air leakage through just a couple of cans can quickly lead to a lot of problems.
An architect would be an excellent source of information on how to properly do this work. Or, educate yourself: buildingscience.com has the information you need.

 

[upsnake]

+1 on this. Not sure of building code requirements in your location, but 2009 IRBC requires R38 or R49 in the coldest climate zones.
There are also important details like those recessed lights. Air leakage through just a couple of cans can quickly lead to a lot of problems.
An architect would be an excellent source of information on how to properly do this work. Or, educate yourself: buildingscience.com has the information you need.

Ya i have thought about the recessed lights those are coming out. Haha. I was thinking of replacing them with two ceiling fans one on each end of the room. (The room is 24 x 11)

Or was just thinking of track lighting in there, but the cans are definitively coming out.

 

[cantoo]

elmoleaf, there are different insulation requirements depending on the type of install. Cathedral rafter(sloping) amounts are less than a flat ceiling joist or truss.
Upsnake, you also have the vertical wall to cathedral rafter joint to be concerned with. Make sure your vapor barrier is continous up the vertical wall and onto the rafters. I've built lots of kneewalls and this is always a spot that has to be watched.

 

[hydrodog]

This may help you

Journal of light construction reprint
http://www.jlconline.com/Images/Tight Cathedral Ceilings_tcm96-1149952.pdf

 

[elmoleaf]

elmoleaf, there are different insulation requirements depending on the type of install. Cathedral rafter(sloping) amounts are less than a flat ceiling joist or truss.
Upsnake, you also have the vertical wall to cathedral rafter joint to be concerned with. Make sure your vapor barrier is continous up the vertical wall and onto the rafters. I've built lots of kneewalls and this is always a spot that has to be watched.

If you are refering to IRBC 2009, can you provide a code section?
I don't see anywhere in SECTION N1102 BUILDING THERMAL ENVELOPE and TABLE N1102.1 INSULATION AND FENESTRATION REQUIREMENTS BY COMPONENT a provision for what you indicate.

Edited to add: I'd be very careful following that JLC reprint from 1990. A lot has been learned since then. Again, I highly recommend research at buildingscience.com.

 

[justchecknjr]

All i can say is do your homework!



i have a guy that is BPI certified, He can help you with all the pros and cons in person. I have been with him on a few quotes, he knows what hes taking about. Not biased to one insulation over another.

At the least call a few insulators in the area and gain some other opinions that see it in person.

 

[GeeVee]

All i can say is do your homework!



i have a guy that is BPI certified, He can help you with all the pros and cons in person. I have been with him on a few quotes, he knows what hes taking about. Not biased to one insulation over another.

At the least call a few insulators in the area and gain some other opinions that see it in person.

Welp.... Yes, I agree to a large extent. Seek advice from those that live an work in your locale.

However- I am skeptical of blanket rules and codes purportenances. Common sense and practical solutions to common problems trumps ALL. In your case- no permit and no inspection would mean you are merely an idiot, and not smart enough to know better- which is negligence. Stupid is defensible, Negligence is actionable.

But yes Too. Your graphic is good. Excellent.

Yes absolutely, getting the radiant barrier correct is the sole key. I dislike plastics. You use insulation both ways.

You don't need much of a nailer, A 3/4" x 3/4" (or 1x1" )strip can be nailed with a trim gun, and the thermoply can be nailed up with a slap stapler or staple gun. From what I saw of your pics, you should have an easy time putting up a tight bit of insulation- properly.

When you have the thermoply, set your blade on your razor knife to extend out about a smidge to cut a wall flap, not enough to cut all the way through the foil side, and score a line, it will fold nicely on that line and not seperate... This after you cut some rips out of a full sheet. You got 16" centers, you get three 14.5" pieces x 96"... or two at 22.5". Score a transverse "flap" at 10" (you have a steep roof IIRC 12/12 P so 10" may be enough to "returnt o the the Wall vertically above the ceiling.) Install the "Wall up the rake" piece first. Then flap another piece as needed (height of nailer) and install top down. Cut filler pieces flat.

I may need to look at your pics again, but only to see the run and rise.....

Thermoply, a trim nailer, and a roofing coil nailer are the hot set-up. A trim nailer is about the only way to get the nailer in place, and it only has to be be big enough to be nailed, the air gap you are providing at 1/2" is PLENTY....

Feel free to PM me for me Phone Number, and I'd be happy to talk with you tomorrow while at work....

GeeVee

 

[deepsouth]

A successful DIY way to kill mould is Oil of Cloves diluted and applied by spray bottle.

Leaves dead mould spores that can be cleaned off or left.

Bleach actually feeds some mould, it doesnt kill all types.

 

[stihly dan]

Welp.... Yes, I agree to a large extent. Seek advice from those that live an work in your locale.

However- I am skeptical of blanket rules and codes purportenances. Common sense and practical solutions to common problems trumps ALL. In your case- no permit and no inspection would mean you are merely an idiot, and not smart enough to know better- which is negligence. Stupid is defensible, Negligence is actionable.

But yes Too. Your graphic is good. Excellent.

Yes absolutely, getting the radiant barrier correct is the sole key. I dislike plastics. You use insulation both ways.

You don't need much of a nailer, A 3/4" x 3/4" (or 1x1" )strip can be nailed with a trim gun, and the thermoply can be nailed up with a slap stapler or staple gun. From what I saw of your pics, you should have an easy time putting up a tight bit of insulation- properly.

When you have the thermoply, set your blade on your razor knife to extend out about a smidge to cut a wall flap, not enough to cut all the way through the foil side, and score a line, it will fold nicely on that line and not seperate... This after you cut some rips out of a full sheet. You got 16" centers, you get three 14.5" pieces x 96"... or two at 22.5". Score a transverse "flap" at 10" (you have a steep roof IIRC 12/12 P so 10" may be enough to "returnt o the the Wall vertically above the ceiling.) Install the "Wall up the rake" piece first. Then flap another piece as needed (height of nailer) and install top down. Cut filler pieces flat.

I may need to look at your pics again, but only to see the run and rise.....

Thermoply, a trim nailer, and a roofing coil nailer are the hot set-up. A trim nailer is about the only way to get the nailer in place, and it only has to be be big enough to be nailed, the air gap you are providing at 1/2" is PLENTY....

Feel free to PM me for me Phone Number, and I'd be happy to talk with you tomorrow while at work....

GeeVee

Are you saying no vapor barrier? They are very important up in the cold climates.

 

[GeeVee]

Are you saying no vapor barrier? They are very important up in the cold climates.

No, not really, vapor barrier is also indicated.

Another option for him would be the 3/4 thick sheet styrofoam, one that has a foil face up. cutting rips 3/4" to make his air gap nailer with, using an adhesive and a few trim nails to hold it while the adhesive sets up is also another option.

 

[Hddnis]

You have to be careful to not end up with two vapor barriers as it were and in a cold climate the vapor barrier cannot be on the cold side or it will collect moisture and literally soak the ceiling. Most reflective insulation products also act as a vapor barrier. In a standard attic they work because both sides are vented. In the OP's application venting both sides is impractical due to space limitations.



Mr. HE

 

[Metals406]

KISS. . .

3" of 2 lb. closed-cell foam, finish with bats -- done. A space sealed with closed-cell foam doesn't need a vapor barrier or ventilation.

Fer Christ's sake, move that stupid door, what a retarded place to put it.

Even if that's a bearing wall, moving the door is easy.

Oh, and don't take advice you get online as Gospel -- call a couple local insulation contractors and have them come out and tell you how they'd do it. Call a few references that they give you (wink wink) to see what kind of work they do.

As mentioned earlier, a lot of times they can be cheaper than you doing it yourself on higher sq. ft. jobs.

 

[Hddnis]

KISS. . .

3" of 2 lb. closed-cell foam, finish with bats -- done. A space sealed with closed-cell foam doesn't need a vapor barrier or ventilation.

Fer Christ's sake, move that stupid door, what a retarded place to put it.

Even if that's a bearing wall, moving the door is easy.

Oh, and don't take advice you get online as Gospel -- call a couple local insulation contractors and have them come out and tell you how they'd do it. Call a few references that they give you (wink wink) to see what kind of work they do.

As mentioned earlier, a lot of times they can be cheaper than you doing it yourself on higher sq. ft. jobs.

The living space might not, but the roof might. Heat kills asphalt shingle roofing and venting the underside of the roof for cooling is covered in shingle warranties. (Not that anyone ever reads them. )

Also can cut way down on AC costs in the summer, meaning a little trouble can pay back in real money.

Otherwise, agree with what you said.:msp_wink:

The balance is that this is the time to think about it, make a plan, then do the work.



Mr. HE

 

[brenndatomu]

The living space might not, but the roof might. Heat kills asphalt shingle roofing and venting the underside of the roof for cooling is covered in shingle warranties. (Not that anyone ever reads them. )

Also can cut way down on AC costs in the summer, meaning a little trouble can pay back in real money.

Otherwise, agree with what you said.:msp_wink:

The balance is that this is the time to think about it, make a plan, then do the work.



Mr. HE

FYI, I checked into this a couple years ago when getting ready to do a re-roof and re-insulate. Most major shingle manufacturers will now honor warranty for shingles installed on spray foamed roof sheeting.

+1 on moving the door, it's not that hard to do, if it'll save you some headaches.

 

[Hddnis]

FYI, I checked into this a couple years ago when getting ready to do a re-roof and re-insulate. Most major shingle manufacturers will now honor warranty for shingles installed on spray foamed roof sheeting.

Good to hear.

I know we had one try to deny a warranty for wrong color shingles because the roof venting didn't meet new codes. A little discussion about involving the state attorney general if they wouldn't honor color warranty claim over venting and they saw it our way and replaced the shingles. I started reading the warranties after that and found venting of the underside of the sheathing to be mentioned in all of them. I did wonder about some of the cathedral ceilings where there is no venting because it is split about 50/50 around here with and without venting in that application. New construction seems to be going without venting more and more. Local inspectors have said that if an architect drew it that way they'll sign off on it, but Joe homeowner has to follow venting codes, which is kind of silly.

I'm guessing that the foam sealing out moisture from the underside of the shingles helps to protect them from the degrading effects of high heat coupled with high humidity.


Mr. HE