[DErnest]

I recently built an addition that has cathedral ceilings. I used 2 x 10 rafters. Do I really need to install the plastic or foam ventilation channels in each rafter??? If I use insulation that is only 6 inches thick then it will leave a greater space for ventilation that the plastic channels will leave. Is there another purpose that is important??? Any advise will be helpful. I estimated that cost for the channels at approximately $500.00 - is it worth this???

Thanks in advance!!

 

[hatchet]

First off - are you using 6" of rigid insulation? I don't think there is a batt type insulation that will give you R-38. Most energy conservation codes required R-38 in ceilings. Aside from that - if using 6" - you don't need the baffles. I would suggest putting them at the eaves of the building if there is even a chance of the insulation blocking the air flow.
Grumpy will probably have more complete information

 

[AaronB.]

The most economical way is to install the channels and use spf one pound foam before you close the ceiling. If if guarantees air flow under your roof deck, thus preserving the integrity of your roofing for its full expected cycle, then I say it is priceless. $500.00 is pennies compared to a rotten or delaminated roof deck.

 

[jmorgan]

Hachet is right. Code requires 2 R-19 batts. This will fill the cavity and actually requires a 12" space, not 10". Of course, if you can get away with only one batt, then you have plenty of ventillation....otherwise, the deflectors are needed. $500 sounds like alot for foam deflectors.
Jim

 

[pondman]

If you built it with 2X10's instead of 2X12's you need to furr it down. Then you can use the baffles in the eaves. Always make your cathedrals 2X12 minimum for insulation purposes.

And yes $500 is a bit much for just the baffles.

Mark

 

[jmorgan]

Good idea, Pondman. Fir it enough and skip the deflectors. Around here most of our construction is 14" TJI's, so we always have plenty of room.
Jim

 

[DErnest]

Thanks for the advice guys. I guess what I really wanted to know was what was the main purpose for the baffles. It sounds like the only reason is to provide plenty of ventilation. Thanks again!

 

[pondman]

Anytime, glad we could all help you.

Pond

 

[AaronB.]

I would never say 500 is too much for anything regarding someone else's work, you fools, until you know the specifics. Friggin ignorance runeth rampant.

 

[Grumpy]

I was actually thinking $500 is cheap for a typical easy installation.