# Insulating and drywalling eichler ceiling



## djcohn (Apr 27, 2016)

This is a bit of a cross-topic post.

I've got a vaulted Eichler style ceiling in my L-shaped living room/dining room with tongue and groove boards over exposed "beams" that are really just two sistered 2x12s wrapped in cheap paneling. There's probably an inch or two of insulation above the boards but it isn't doing much to keep the room cool in the summer sun, even if the upstairs is perfectly cool. The thermostat is in this room. Additionally, we want to install cans to get more light in the rooms.

So I'm thinking of installing furring strips and drywall to the underside of the beam after installing some sort of insulation and cans. My questions are:


The space between the drywall and current ceiling would be unventelated. Is that ok?
What type of insulation should I use? I was thinking some sort of rigid foam, but there are many kinds. Or should I be using batt insulation? Spray foam is probaby cost prohibitive.
What R-value should I target? Cost is a factor for sure, but I dont want to save a few bucks and then have insulation that doesn't do jack squat.
Any specific recommendations on how to support the drywall and what orientation? The beams are about 40 inches apart and 4 inches thick, and from the outside wall to the apex is about 13.5 feet.
What thickness drywall would you recommend?

Thanks in advance


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## Windows on Wash (Aug 30, 2011)

Questions for you:


What is the roofing material that is above that section
Is there an overhang
Where is the home
Answers:


I can work. As long as you have an air impermeable insulation and haven't noted condensation issues previously, there shouldn't be any reason that you can continue the air/insulation barrier thickness. I would be wary of any air gaps that might allow roomside moisture to diffuse or move via bulk air transfer up to the T&G. If that happened after you insulated, you most certainly would have a condensation issue as that T&G would be much, much colder than it is now as the room heat warms that surface.
Spray foam is ideal here because is automatically (installed properly) forms the air barrier with the insulation. Rigid foam and batt insulation can work but you really need to get it well sealed when you do it. Where the home is and what the condensation potential are is also important here.
Depends on where the home is as to what is going to be effective, but R-38 is typically what you will see as a default in a ceiling.
https://energycode.pnl.gov/EnergyCodeReqs/

Consult the drywall manufacturer as to what they require in terms of span and board thickness in a ceiling application. I think you are going to need to frame in some intermediary support.
See above.


Good luck. Depending on the square footage, I think you have a decent sized project on your hands.


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## djcohn (Apr 27, 2016)

Sorry, i thought I had mentioned in my previous post that I'm in Chicago. Guess I didn't.

The roof is asphalt shingles


By overhang do you mean the roof overhanging the side of the house? If so, yes, it's about 2 feet on one side of the house, and the other side of the house the roofline continues out to become a carport. Both sides have soffit vents. I can't tell, but I don't think the air gap continues into the area of the roof over the house, I think it's just in the overhang. If I broke through the wall inside in the area that would be closed in, I'd be breaking into that space I think, but I don't know yet if there's brick there or not, and I really don't want to start with breaking through brick.

I know that the better way to do this would be to tear off the roof, insulate above the sheathing and put on a new roof. With my current solution I'll be conducting some heat through the beams. When I'm due for a new roof, I might do that as well, but for now, I don't have the money for a new roof, nor is it due to be replaced yet.


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