Many discussions of structural insulated panels come around to a concern that they don't fit well with the idea of a 'traditional' house. A friend and his wife gave up on timber framing over their refusal to live in a home "wrapped in toxic foam." [not looking for an argument over the relative merits of existing foam types - people are going to have opinions regardless of facts...]

Not a real concern for me, but I am curious; has anyone ever proposed building an SIP panel with some less controversial insulation? The way panels wrap the house in a tight seal while revealing all of the timbers to the building interior is hard to beat. Anyone ever consider offering panels with some sort of "green" filling? [brown rice husks, the fur swept up from your local pet rescue center? something more practical?]

Seriously, any alternatives to the two leading foam types?

SIPS have been filled with mineral wool, wood chip, cellulose and probably all sorts of other things, though it's probably not accurate to call them SIPS anymore, when the skins are not mechanically bonded to the insulation.

Sip=Structural Insulated Panels

To me any insulated panel that is structural regardless of material would be a SIP.

There is a company in western Canada that sells a product that I think is from Germany. It is a panel filled with wood that has long fibres and looks a bit like a rough wool.

I have a friend that is building a 2x4 wall outside his frame and spray foaming the cavities of that with a soy based spray foam.

straw SIPS
http://www.agriboard.com/panels_from_agriboard.htm

and a good read on soy based spray foam...
http://oecotextiles.wordpress.com/2010/01/27/does-soy-based-foam-deliver-on-its-promise/

You should check this out:

http://www.youtube.com/watch?v=nV-iCIqRn28

See the shaving infill part from the 3rd minute.

www.baufritz.com

It is a German house manufacturing company that makes passive houses for wall infill using wood shavings.

Here are some good stuff about shavings:

timber.ce.wsu.edu/Resources/papers/4-2-1.pdf

An alternate method and I think the worlds best insulation is sheep wool insulation:

http://www.sheepwoolinsulation.ie/

I just saw nebruks first video, and it looks like sawdust/wood chip. One thing to keep in mind, that yes, Sawdust would insulate, but we all know how flamable/explosive sawdust is.

Whatever insulation method is used, fire must also be a primary consideration. I wonder if that's why light clay is used with woodchip and straw? Or if that is just an additional benefit?

Light Clay is a very good alternative in my mind. The walls end up being thicker than a conventional SIP but there are so many more advantages to light clay.

Light Clay works excellent with a timber frame. Uses natural non-toxic materials (clay, wood shavings/chips, or straw). Light clay is a good insulator (about r-25 in a 12" wall) but where it really excels is in its ability to be a heat sink. During the day it collects heat from the sun or from a wood stove and at night it lets it off when temperatures drop. This is called Thermal mass and is most often overlooked when designing a house. With Light Clay you can also use materials collected right from the site, no trucking involved!

I also find that Light Clay building is also very calming to be in. It is way different than a conventional house. Clay holds negative ions, which help to calm your mood. Clay is also an air purifier; it can help take toxins out of the air.

Clay is highly hydroscopic which means it will take on a huge amount of moisture and let it off again without any damage to the wall. This is great in high moisture rooms like Kitchens and Baths.

A Light Clay wall is also designed to breathe; there is no moisture barrier like a conventional home. In this regard I believe there is no need for an air exchanger. Your house becomes a much healthier environment to live in! There are examples of Light Clay/Timber Frame building in Germany that date back 900 years or more and have been lived in the whole time. How's that for longevity!

Cheers,
Tim

There is a big difference between sawdust and wood shavings.
I am not talking about large shavings that come for example from traditional hand plane. I am talking about the shavings that came out from the large machine planer.
I have collected shavings that I will use from my friend-carpenter that makes pine wood windows and doors.
The shavings insulate much more better cause there are much more air between the shavings (compare to the sawdust) when they get lightly compressed and infilled in the wall. The clay proportion I am talking about is dry clay as a powder that is being mixed with the shavings. The clay is mostly added to prevent fungus attack - so the mouse do not like to make a home where the clay is.

Tim, thanks for your input on this, I've been following your blog/site for quite some time now

The light clay/shavings/straw is something I'm considering for two thermal walls I'm building but am also interested in using this technique for the 2x4 curtain walls on our frame. The walls are already insulated with 5.5" of exterior polyiso (yes I know...way too foamy, but at the time it was the only manageable way to enclose the frame for me). Now it's time to put a natural "buffer" zone. With polyiso being impermeable, do you think the slip technique can still be used and allowed to wet/dry to inside only?

Hmmmmm....I am not quite sure what you are asking? Are you asking if you can put a 1' thick light clay wall on the inside of the polyiso wall? Or are you asking if you can plaster onto the wall?

I would not recommend putting a light clay wall on the inside against the poliso. With this I don't think the wall would dry properly, or would take a long time. A normal light clay wall can take 6 weeks or more to dry fully.

If you are asking if the iso board can be plastered onto, then yes this is an option. I just helped do this on a friends house about a month ago. It worked really well!

I hope that answers your question?

Cheers,

Tim