Vaulted Ceilings

Weekend Warrior DIY

Okay, quick question, I installed R-19 fiberglass insulation in my vaulted ceiling, in 2 x 8 rafters. Someone, plumber on site, mentioned whether or not I was going to use the foam 'egg crate' things for ventilation.

It got me thinking but R-19 is less than 6" and the rafter is 7 1/2", I believe I should have plenty of an air gap between the ridge vent and the eves.

Please let me know your thoughts.

gwilkrrs

i am required to have a 1" air space between the insulation and the bottom side of roof sheathing here......

Weekend Warrior DIY

I don't know what we're required to have, SE PA, but I have at least an inch so I think I'm safe. I will find out soon enough.

joecaption

Go back and add your location to your profile, yes it makes a big differance!
http://www.energystar.gov/index.cfm?...sulation_table

Gary in WA

BSC recommends 2" gap as 1" (minimum code) is not sufficient, baffles all the way; http://www.buildingscience.com/docum...n-roof-venting

Gary

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Weekend Warrior DIY

Thanks for the replies. There's about a 2" gap so I think I'm set. I guess if I'm wrong the BI will tell me when they come out.

Gary in WA

Cathedrals require baffles or you will wind-wash the fibrous insulation, negating its R-value 40-60%. http://www.reedconstructiondata.com/.../pennsylvania/
As the outdoor air deposits its moisture on the insulation (great filter- think furnaces), expect 60-70% R-value loss; http://archive.nrc-cnrc.gc.ca/eng/ib...ling-heat.html

Expect to add 2x6 furring to the rafter bottoms before/after inspection to reach code minimum R-38, unless the inspector accepts R-30; http://publicecodes.cyberregs.com/ic...9_4_par004.htm

for your State- under the IECC, 2009; http://www.reedconstructiondata.com/.../pennsylvania/

This should all be listed on your approved plans for the permit...

Gary

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AndyGump

Are your ceilings vented?
Do they have blocking in them that would prevent air flow from eave to ridge?

Andy.

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Residential Drafter/Designer

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Weekend Warrior DIY

Yes, my ceilings are vented via a ridge vent and eve vents.

GBR, I researched the links you referenced and even though they look 100% correct, the house was built with 2 x 8's and inspected as such. Why in the world and how could the BI require me to put in R-30 or higher which requires a higher rafter after it was all inspected and approved?

Doesn't make much sense to me.

Gary in WA

Me either. Your whole state is under that Energy Code, with no local amendments. My state requires R-49 (Zone 4 marine) as we have our very own Energy Code, so fortunate to go above and beyond the IRC, IBC, and IECC code minimum...surprised they didn't say anything before.

Gary

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gwilkrrs

wen was your permit aproved?on your drawings did they call out the r values on the wall and roof sections? my permit was pulled last year prior to them updating the code so i fall under the older values. on my permit drwaings he highlighted te note on wall sections and wrote R13 and such. i had a long conversation with the building inspector on this as mine was stick framed with 2x12 rafters for a cathedral cieling- and how to insulate this properly and to achieve the r factor. under the current code this is impossible and now requires te rafter to be padded out or a scissor truss to be used to achieve this......

great links by the way....

Weekend Warrior DIY

Last year, around July-ish. Per my township the homeowner is allowed to produce their own drawings. I was checking them out the other day and there's nothing on there stating anything about insulation, etc. The only thing called out is with regards to needing permits for anything else, i.e. electrical, plumbing, mechanical, etc.

Gary in WA

I'd give the field inspector a call and ask him. Let us know the outcome...

Gary

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