exposed rafters

Old 10-03-01, 10:38 AM
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Hello everyone,

This is my first post. I am hoping someone can help me with my problem.

I have just purchased a "cabin" on a Lake Wabuansee in Kansas. Actually it was a P.O.W. camp during WWII for ****'s.
These are old barracks that they have walled off at mid point, making two "cabin's". I bought it gutted and have decided I would like to leave the vaulted ceiling open. Another words, exposed rafters. I would like to add cleats to each side of the rafters and face the space between rafters with old barn wood. My problem is I'm not sure how/what to insulate with under the barn wood. My concerns are moisture, condensation and if I need to add vents at cap, eaves or what. I cannot find any literature on this subject. Anyone have any ideas?


Michael T. Stark
Old 10-05-01, 05:52 AM
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Your concern about moisture is justified. You also have the problem of about 20-30% more ceiling area than for a flat area, so, your heat gain/loss is much greater than a flat ceiling.

I have done many of these and you should have venting above the insulation. See The will tell you the proper ratio.

You didn't give the rafter dim., So, I will give you some alternatives.

I am recommending high efficiency, 97%, radiant barriers (RB) because any other type of insulation would only be about 10%, (fiber glass} or 20% (foam). As you know they can create moisture problems, the RBs can't. The RB will also act as a very effective vapor barrier. The RB will take up the least space and out perform the other two for summer and winter.

You need a minimum two layers of RB. I'm recommending two because you probably have odd rafter widths and the two single layers will be easier to work with on odd ball widths. You didn't say the c/c, but, I'm quessing 24" max.
Install 2x2 between the rafters 24"c/c about one inch down from sheathing (vent space). Install one layer as close to the top of 2x2 as possible. DO NOT INSTALL ON TOP OF 2x2.
Install the second layer about 3/4" below the first layer.
Attach your dry wall and finish.

You could use a 2x3 or 2x4, but, that would reduce the amount of exposed rafter.

If you are more concerned about energy savings than exposed rafters, then do the following.

As good as the RB is, tou still have above normal heat gain/loss thru the rafters. To minimize this, install as follows.

Install between the rafters, lenght ways, one layer of RB between the rafters about one inch up from the bottom surface of the rafter.
Install second layer to the bottom surface of the rafters.
Install ACROSS the bottom surface of the rafters 7/8" steel furring channel. Install dry wall and finish. You can install fake beams if you want.

I'm guessing that this is single story. If you do the walls and crawl space(?) with the RBs you will have a very efficient house with no moisture, mold or insulation induce dry rot. Maximun a/c per 1,000 sf., 3/4 ton.

Thank you for considering my opinion. If you have any ?'s about method or source of material, let me know.

For RB info, enter into your search engine, "radiant barriers" "or reflective insulation".
Old 10-05-01, 11:57 AM
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Thumbs up exposed rafters

Thanks rbisys,

Thank you for replying to my post. I greatly appreciate it.

I will look into your suggestions and visit cor-a- Sorry I didn't give c/c, but you guessed right. I have read about RB and I'm greatly concerned with the above normal heat/gain loss. The fake beams are a great idea.


Michael T. Stark

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