Japanese roof logic

Traditional framing and building practices, using wood, stone, straw, clay.
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Chris Pyle
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Re: Japanese roof logic

Thu Mar 05, 2015 12:04 pm

So having said that and following along with your logic, what methods can be employed to create timber structures with adequate thermal insulation, proper breathability for air exchange and using materials that aren't off-gassing, energy-intensive in their production, etc?

I've been searching for a good solution to this problem and have yet to find it. There seem to be two camps: people who say you must adapt current practices because the economics dictate it (both in time spent building and in materials) and those who say you should adopt frameworks seen in the past with a little modern revision: strawbale, thatched roofs, etc.

I've seen old posts of yours referencing the Larsen truss where you essentially develop two framed walls gusseted together and filled with an insulative material of your choosing (blown cellulose, etc).

I would love to have a timber frame home or shop, as I am naturally drawn to them, but current practices leave a lot to be desired.
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Chris Hall
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Re: Japanese roof logic

Thu Mar 05, 2015 6:21 pm

Cellulose has high insulative value, however it can settle within the walls creating dead spots, and if you wish to make modifications to the wall it can be messy and requires a sprayer to reinstall. Not huge obstacles by any means, just inconveniences.

Also, with a cellulose infill, you must contain it within two layers of vapor barrier to prevent it gaining moisture. Problem is, if someone drives a nail into the sheetrock to hang a picture (etc.), or a screw t mount a shelf, then they create one little pinhole, and possibly many if they hang lots of pictures, which can affect the cellulose I would think.

I live in a house with cellulose insulation. It's warm and dry, but it wouldn't be my first choice for an infill.
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Chris Pyle
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Re: Japanese roof logic

Thu Mar 05, 2015 9:19 pm

So, what would be your first choice of infill? Do you still like the Larsen truss system?

Is there a better method that you envision for making use of the structural and aesthetic value of timber frames? I don't think the frame must show externally, which is why the Larsen truss wasn't a bad option.

Any thoughts you care to share?
jamie shard
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Re: Japanese roof logic

Fri Mar 06, 2015 10:41 am

Chris Hall wrote:Oh, I have many ideas in that regard.
...
Most of the North American solutions revolve around jacketing the frame with SIPs or straw bales, neither of which strikes me as a good solution.
I'm also interested. Your blog posts on timberframe+SIPs and balloon/stick construction were great, but kinda left me hanging with the question on how to resolve the issue.

These were some great blog posts:

http://thecarpentryway.blogspot.com/200 ... touch.html

http://thecarpentryway.blogspot.com/200 ... h-too.html
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Chris Hall
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Re: Japanese roof logic

Fri Mar 06, 2015 8:49 pm

I don't mean to be abstruse, it's more that I would prefer you to draw your own conclusions from different trains of thought/various observations and not simply lay out on a platter what I have concluded.

I've never spoken up as a fan of the Larsen truss system, I think at best I've mentioned it as one option out there. Econest uses it. It doesn't appeal to me primarily because it is a wooden structural system which is concealed, and tends to make use of plywood, and loads of fasteners. It has some plusses of course, but it's not what I would do unless looking to retrofit an existing structure.

Let's step back a moment - - if you wanted to eliminate thermal conduction through a single pane glass window, you can do so by going to double pane or even triple pane. You can create thermal breaks within the window frame. You can add into the mix argon gas instead of air, and use low-e coatings. There's a cost/benefit analysis in there that, depending upon the climate and the heating load, might sway things one way or another, triple pane being a fair amount more costly than double pane.

When it comes to a wall, how might one reduce or eliminate thermal bridging? I mention this at the outset as a reduction of thermal bridging is one of the cornerstones of Passiv Haus.
AntoineLaMothe
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Re: Japanese roof logic

Sun Jul 12, 2015 8:10 pm

Well, our frame is up. The simplified timber frame was a bit awkward to raise at first, as there were no horizontal members before the 10 feet high main beams... We had to raise the basic square (rectangle...) and then directly install the also simplified stick framing and temporary bracing in order to add the roof. Things went well, the raising of the crooked beams was done with a "trepied", a very simple tripod holding a chain block. The rest was done by hand, as the largest beams were 6x8 and not too long. The structure is not perfectly sturdy along the 30 feet wall, since there is no inside wall to stop it from bending. We didn't want diagonal bracing or posts inside, so we'll have to live with it. I guess closing the walls will help a lot, and it's not that bad at all, but... we'll see!
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IMG_3855.JPG (172.07 KiB) Viewed 5492 times
Hempcrete will start in 7 days. I will let you know how it goes.
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IMG_3856.JPG (347.97 KiB) Viewed 5492 times
Last edited by AntoineLaMothe on Sun Jul 12, 2015 8:17 pm, edited 1 time in total.
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Chris Hall
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Re: Japanese roof logic

Sun Jul 12, 2015 8:17 pm

Fixed the rotation on the first pic for ya..
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Chris Hall
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Re: Japanese roof logic

Sun Jul 12, 2015 8:17 pm

Why no bracing?
AntoineLaMothe
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Re: Japanese roof logic

Sun Jul 12, 2015 8:22 pm

Thanks Chris.

I just tried to make the second picture smaller but I get a "no access to this file" message... It doesn't bother me if it doesn't bother you!

No bracing in the walls since any horizontal member is a pain in the neck for hempcrete (!), and because the hempcrete itself is more that adequate bracing. No bracing inside the building (hope I'm clear), where we would need some now, for aesthetics reasons only.

I've never built a house before so I don't know what is ok and what is not in that regard. It might not be a problem at all. If it is though, we will probably have to add some members, wich is not very nice.
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Yxoc
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Re: Japanese roof logic

Tue Jul 21, 2015 6:10 am

Looking good Antoine!

Please keep us updated as the hempcrete goes in.

Derek

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