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
