I'm planning to start building next year on a very windy ridge on 40 acres in Weed, CA (that's right, WEED !), high on the slopes of Mt Shasta. We'll be erecting small vertical axis wind turbines to show proof of concept. I've chosen a Quonset hut design for aerodynamics. Rather than try to insulate the INSIDE of the roof, I hope to spray the outside with hempcrete (http://en.wikipedia.org/wiki/Hempcrete) for its green properties and superior thermal insulation. I plan on adding helix fiber for strength, rather than rebar. http://www.helixfiber.com/ . On top of THAT I hope to roll the entire roof with sod (grass) for more thermal insulation and green aesthetics. It should give the building a great "hobbit" or "teletubby" look... Anyone experienced with hempcrete ???

I doubt that you will get much positive feedback on HempCrete from anyone with experience in the building industry. IF you choose to go that direction, make sure to consult your local building office to see if they will accept it, as I assume there is no code research report.

Hi Jimmy,
I am currently writing a dissertation on Hempcrete and can advise you that it would not be suitable for the application you are planning. Hempcrete it primarily a breathable insulation composite for use in walls, floor slabs and indeed in roofs. However, it is not impermeable and requires either an external lime render or cladding to protect it from exposure to driving rain. Should it be exposed to this (as in a roof covering) it will over time absorb more water than it can dispose of and the Hemp Shiv within the material will begin to rot.
If you do decide to use it as an insulation material in the roof structure ensure that it is not exposed to the elements and there is a sufficient amount of ventilation to allow water to escape.
More information can be found at;
http://www.limetechnology.co.uk/hemcrete.htm
Hope this helps, Paul

waiting to exhale.
What dose this have to do with icf?