Insulation, Radiant and Vapor Barriers - skylight-does it need vapor barrier if in vaulted ceiling? -need answer ASAP

I have addition that has shed roof and skylight in center. I decided not to but up ceiling joists and left it vaulted. it was originally built with 2x8, but to get the space for required R-38 insulation the carpenters added 2x4 to the bottom. The insulation has been put in. The put up the baffles from soffit to top (I was told by inspector that I should have roofer put vents at top near where the roof meets the wall of old house) The rest of the space is occupied by the insulation. The company doing insulation said that since the entire "chase" of skylight is filled with insulation that no other vapor barrier is needed. Is that correct?

Drywall being put up tomorrow. we noticed that the frame for the skylight needs to be furred a little. On one side I had to add a 3/4" piece of plywood and on two short sides I need to add 1/2" sheet of plywood that will have to be tapered to 1/4". so do I put anything to fill the gap that will be created between the framing and the drywall. See photo showing the 3/4" plywood in place.

http://i42.photobucket.com/albums/e311/hammerash/DSCN5585.jpg

Going back one step, what's the pitch on that roof?

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Also, best practice is to allow airflow past the skylight:

http://paragoninspects.com/images/vent/attic-roof/skykight.jpg

thanks for the pic. I had thought about something like that. I think I will try to do some holes tonight. I don't see where the ones on high side are really needed though? the air goes up toward skylight, over through the holes and then upward to peak. the high side of skylight bay just goes up to peak.

the pitch is 4/12

ran into a problem. took some insulation out below skylight and they didn't put any of the baffles in those bays. I did see baffle in bay next to skylight. I am going to have to go to peak and pull each one to see if baffles are there. I would have to cancel drywall to get some baffles and drill holes. but another thing is the bay is only about 11" deep so need the baffles to create air pathway. but hard to drill holes connecting bays since the holes would have to be way at top of the 2x8 rafter (so air spaces created by baffles up high could communicate) but you can't really drill holes in that location. holes should be in about middle of rafter? options to ventilate the bays below skylight?

Little late now, but the slick way to do it is with "RafterVent" (http://www.dciproducts.com/html/raftervent.htm)

There is also a special vent I see from time to time designed for the intersection of you shed roof with a wall - I've got the name around here somewhere, THAT you still might be able to do.

ran into a problem. took some insulation out below skylight and they didn't put any of the baffles in those bays.

Probably, they didn't seem much point in doing so, as ( at least the way they installed it) there is no vent at the high-end.

Found it, same company:

They suggest using their eave vents at the roof/wall intersection:

http://www.dciproducts.com/images/shed-500.gif

Here's what's allowed in terms of notching and boring:

R802.7.1 Sawn lumber. Notches in solid lumber joists, rafters and beams shall not exceed one-sixth of the depth of the member, shall not be longer than one-third of the depth of the member and shall not be located in the middle one-third of the span. Notches at the ends of the member shall not exceed one-fourth the depth of the member. The tension side of members 4 inches (102 mm) or greater in nominal thickness shall not be notched except at the ends of the members. The diameter of the holes bored or cut into members shall not exceed one-third the depth of the member. Holes shall not be closer than 2 inches (51mm)to the top or bottom of the member-, or to any other hole located in the member. Where the member is also notched, the hole shall not be closer than 2 inches (51 mm) to the notch.

yeh, that stuff would have been nice. so what can I do now and is it worth it? Here is what I thought about doing. take piece of baffle and cut it so it will fit sideways in each bay. cut holes in rafters so they communicate. then cut the side of that piece so that you can shove another baffle into the first. the second will run the normal direction of the rafters. so the holes would have to be cut in a 8" long by 1.25" deep rectangle at the top of each rafter. see pic with blue square-actually trapezoid I guess. is this worth it? lot of work for me to do as this skylight is 44" across and will have to delay drywall. what size holes and how many? I see benefit of doing up top as well as bottom. My concern with this is just drilling so close to edge of the rafter? although I guess it really isn't supporting much since the lengths are so short till you hit the header of the skylight-then all weight transferred to the king rafters (don't know if that is actually term used but you get point)

http://i42.photobucket.com/albums/e311/hammerash/DSCN5600.jpg

http://i42.photobucket.com/albums/e311/hammerash/DSCN5599.jpg

http://i42.photobucket.com/albums/e311/hammerash/DSCN5602.jpg

looks like our posts crossed. so if I cut holes 2" from top edge, they will not be able to communicate through the rafter vent that I have since it is only 1.25" deep. so my plan won't work. Any thoughts what I can do at this point? I already spoke to drywall and told them there was problem so I can delay drywall IF there is something to do and if worth it. back to my original question-any vapor barrier needed or since surround by insulation is it not needed?

Hi, just read your post. Sounds like Michael is taking care of you.

1. I can't make out from the pic, is that label 38 or 38C ?

2. Here it says R38 is 12" thick, R38 C is 10-1/4". 2x8 = 7-1/4+ 3-1/2 = 10-3/4" minus 1" air space is 9-3/4", correct?

http://www.fibertekinsulation.com/products/big_batt_kraft.pdf

3. The insulation should be stapled so the bottom edge of flange is flush with bottom of rafter. It's already tight by 1/2", so anything less is not good (less air space).

Look over the ceiling for all insulation flanges flush.

4. The vapor retarder is already installed (kraft paper).

5. 1-1/2" holes 1-1/2" down, 4" apart times 3 is fine. Even if you notched higher, it would reduce the rafter down one size to a 2x6, which still spans 11'9" (no snow load) x 24" o.c. or 14'1" x 16"o.c. (no snow load)DF#2. (I would stay away from the roofing nails in the very top of rafter).

6. What R- rating on insulation? Be safe, G

R38 not R38C. I guess it should have been R38C. what is difference and how can it be thinner yet still have same R rating? so I am really tight --2 1/4" less than the 12" batt using 1" as air space. so if I am going to drill 1 1/2" holes 1 1/2" from top, with the intention of having open communication between bays, my air space is then 3" ( 1.5 + 1.5 to bottom of holes) meaning I would be 4 1/4" short of the 12" batt. doesn't seem too good. And I don't have anything to keep insulation that far from roof deck since the baffles are only a little over an inch thick. Am I better of just not doing anything? or can anyone think of something.

Contact the installer, ask him how this can work being the wrong application. Contact the manufacturer, ask him if the web site is current and tell him your joist depth.

You're losing 17% of the insulation value already, not counting the poor application where it is pushed up the joist space (compressed).

Be safe, G