Helpful? 0

What barrier should I use under wall shingles to increase insulation in a single wall cabin?

I have a 100 year old redwood cabin in Northern California in the coastal area.

It is single wall construction consisting of 1x12 redwood boards and framing visible on the inside, and with cedar plank covered by redwood shingle on the outside.

I am replacing the shingle and will be repairing damaged cedar plank as necessary.

I do not want to turn the cabin into double wall construction with interior insulation as it will wreck the character.

In addition to building paper, what can I use between the ceder plank and shingles to increase the energy efficiency of the cabin?

Please take into account that this old redwood should not be wrapped in a plastic bag as it needs to breath in this foggy climate.

Thank you,
Mark

Asked by Mark Darley
Posted Wed, 09/19/2012 - 13:35

Tags:

9 Answers

Select your preferred way to display the comments and click "Save settings" to activate your changes.
1.
Helpful? 0

Mark,
I advise you to install a layer of rigid foam; polyisocyanurate is the most environmentally friendly foam. The thicker the foam, the higher the R-value of the resulting wall.

On the exterior side of the polyiso, you'll probably want to install a layer of plywood or OSB. Then you install your asphalt felt, and then you install your shingles.

Such a wall will be able to dry out in both directions. The shingles and plywood will dry to the exterior; the redwood sheathing and the studs will dry to the interior.

Answered by Martin Holladay, GBA Advisor
Posted Wed, 09/19/2012 - 13:56

2.
Helpful? 0

Good recommendation! Adding 1.5" of iso with taped-seams with an OSB nailer for the shingles through-screwed 24" o.c. to the framing with pancake-head timber screws would yield a wall only 2" thicker than where you started, but it would outperform most 2x4 batt-insulated construction due to the air-tightness and low thermal bridging (no framing penetrates through the ~R10 insulation, only screws every 24".)

Take care to not ruin that with extra-long nails for the shingles- keep them so that they don't penetrate the iso by more than 1/4".

Answered by Dana Dorsett
Posted Wed, 09/19/2012 - 16:23

3.
Helpful? 0

Mark,

If you want to maintain the natural material list, I think Expanded Cork Insulation Board could be a good option for this project. It's apply's like the Polyiso that Martin and Dana suggest, insulates at around R-4 per inch, remains permeable, but is nothing but real tree bark expanded into an insulation board.

You can read an independent review by Alex Wilson here: http://www2.buildinggreen.com/blogs/expanded-cork-greenest-insulation-ma...

Our (rather long winded) info page on Cork is here: http://www.smallplanetworkshopstore.com/cork/

Take care of that old redwood. Your lucky to have it!

Answered by albert rooks
Posted Thu, 09/20/2012 - 02:28

4.
Helpful? 0

Albert,

I am intrigued by the cork option. I remember fondly discovering rooms in Portuguese home lined in cork for sound insulation. Many monastries used cork.

Do you have any idea how it holds up to beetles? Beetle damage is common in the area where I have the cabin in almost any wood except redwood (which fortunately accounts for 80 of the timber in my cabin).

Is there a really thin material that is efficient, say 1/2 inch thick or thinner?

If I take all the shingles and then the sheathing off the exterior of the cabin, and start with new insulation and then build up with new sheathing and shingles, I will have to re-trim all the windows or they will all be inset below the level of the shingles. Not an impossible task, but just another added cost.....
Thanks
Mark

Answered by Mark Darley
Posted Mon, 09/24/2012 - 13:45

5.
Helpful? 0

The cabin in question images files attached (may not be reproduced without permission).

WeeHousie_05copyright.jpg WeeHousie_06Copyright.jpg
Answered by Mark Darley
Posted Mon, 09/24/2012 - 14:02

6.
Helpful? 0

Mark,

Yet another incidence of a "small world". I just checked back on this post this morning and found your question. Since I wasn't sure, I checked with Portugal (Amorim) and found that you had made an inquiry yesterday. Francisco (at Amorim) just answered both of us. His reply to the beetle question is:

"Regarding beetles, historically we have no claims which is a good indicator. The reason might be because when cork when is processed into expanded insulation cork board due only to the action of steam and pressure (we say when cork is cooked) the Expanded Insulation Cork Board will be a carbonized material so there is no cellulose or food available for any bugs."

The food being "cooked out" is an interesting situation. I like it.

Answered by albert rooks
Posted Tue, 09/25/2012 - 09:03

7.
Helpful? 0

Mark,

I did not answer your thickness question. The thinest panel that we can buy is 1" thick. I've got plenty of 2" & 4" thick on the way and will order some 1.5" thick also.

For your project, I think I'd go for the extra long term value and put 1.5" to 2" on the walls and re-trim all of it. A thin layer seems like too much work for too little insulation.

Btw... We can get a higher density cork that is made to be the facade. Perhaps you only re-shingle part of the cabin, and certain "accent area's" are sided with natural cork as the final facade. That could look dynamite!

Your own monastery in the woods.

Answered by albert rooks
Posted Tue, 09/25/2012 - 09:11

8.
Helpful? 0

Albert,
Indeed a small world. And this is the site that helped me find you.
I was considering using cedar lapstrake below the floor level, and shingle above both for looks and speed of application. It is a traditional look in the neighborhood. Maybe that should be shingle above and cork below (or the other way around for greater insulation value) for an interesting look.

Answered by Mark Darley
Posted Tue, 09/25/2012 - 14:58

9.
Helpful? 0

Or the 1927 bumped out sleeping porch (see right side of exterior photo) could be sided entirely in cork with the rest of the building shingled....

Answered by Mark Darley
Posted Tue, 09/25/2012 - 14:59

Other Questions in GBA Pro help

Wet OSB - how much water can it take?

In General questions | Asked by colleen1 runyen | Dec 17, 14

Meanwhile at BSC ... PHIUS draft standard

In General questions | Asked by Jin Kazama | Dec 12, 14

Quarter Round on Rammed Earth

In Green building techniques | Asked by Terry Lee | Dec 18, 14

Is this furnace venting/leaking problem as bad as it looks?

In Mechanicals | Asked by Nathaniel G | Dec 20, 14

Polyiso for basement

In Green building techniques | Asked by sr kod | Dec 20, 14
Register for a free account and join the conversation


Get a free account and join the conversation!
Become a GBA PRO!