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How do I properly insulate and ventilate a roof with a cathedral ceiling and single peak?

I am building an 88 square foot office studio that I would like to be sure it is well insulated. Here's a picture of it: http://www.summerwood.com/plans/home-studios/catalina/1045/detail.html

My question is how to properly insulate the roof.. As you can see from the picture, it has 5 sides and the roof has a single peak. The rafters will be built with 2x8s. I am planning on sheeting rocking the inside ceiling. Should I:
1. Insulate with batt FG insulation between the rafters and install soffit vents in the eaves to be sure the roof is properly ventilated along with ridge vents along all 5 of the ridges?

2. Put rigid insulation on the outside of the roof sheathing and then add another layer of sheating to nail the roof shingles to..but do this with-OUT ventilation?

3. Other options?

I'm really stuck on this one so advice would be much appreciated.

I live just outside of San Francisco, so fairly temperate climate but I do want this studio to be comfortable especially on cold/rainy days.

Thanks in advance!
tom

Asked by tom maz
Posted Sun, 01/12/2014 - 03:53

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Tom,
This type of roof does not lend itself to a vented roof assembly. The solution is to build an unvented roof assembly.

To read about the different ways to build an unvented roof assembly, see How to Build an Insulated Cathedral Ceiling.

Answered by Martin Holladay, GBA Advisor
Posted Sun, 01/12/2014 - 08:15

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