The Eden Project is a multi-biome park in England somewhere where they've built these amazing huge greenhouses for visitors using a transparent material called ETFE foil. It's a transparent polymer that's used as an architectural membrane in some new structures (although one's been around for at least 20 years) and it's tough and much, much lighter than glass. What they do is make a multi-layer pillow of the stuff and inflate it with air in the middle to give it a convex shape and good insulation properties.
I found an interesting mailing list called Greenbuilding; here are the Greenbuilding archives .
A useful concept in designing an efficient building is to know about embodied energy . The embodied energy of a material is the total amount of energy needed to create it and deliver it to you -- extraction from the ground of raw material, cost of production, cost of delivery. You can use a higher embodied energy material if your building will last longer or if it will give you better efficiency in other ways (such as ongoing power costs).