Does anyone here have any experience (or thoughts) on the Walipini greenhouse design?

not familiar with it..i have a "too small" small greenhouse that is double wall polycarb with alum frame..i like it but of course would prefer a larger greenhouse someday..

mine has no supplemental heat so it is restricted in it's use

Sounds like home...too small and no sup heat.
Walipini is an underground greenhouse with rammed earth walls.

http://bensoninstitute.org/Publication/Manuals/index.asp

Budget permitting, I'm considering a polycarb roof.

What's your take on the twin wall?

From the looks of the PDF it seems like it's a mike oehler type greenhouse with rammed earth walls and no cold sink.

And with a more elaborate drainage system than Mike's.
I have a lot of ideas spinning around in my head. One is to heat it with biomass, a la Jean Pain. I literally have easy access to tons of wood chips.

I would suggest that you first take a look at Mike's greenhouse book:



http://www.amazon.com/exec/obidos/ASIN/0960446400/rs12-20

I think that if you combine some of Mike's ideas with the wofati ideas, you won't have to bother with the wood chips.

Thanks, Paul. I've had Mike's $50 and Up book since the early '70's. Read it then and it's been on the shelf ever since....or was until the grandkids moved in. I'll pick up his greenhouse book. I've been going over your wofati ideas and see some interesting things there. I suspect I have much the same mentality as you with regards to cheap and readily available materials. My problem here is logs are neither cheap nor available in quantity. Dirt and wood chips fit both criteria (both are free). Composting the wood chips has the advantage of providing large quantities of fertilizer needed for an acre+ of garden. I've been composting chips on a smaller scale for several years.