I'd get a copy of this book:
Solar Greenhouses and Sunspaces by Adrew Shapiro
It is the best of the greenhouse/sunspace books I have run across, and
includes design procedures for greenhouses that are intended only
for plant growing as well as ones intended for home heating and plant
growing. There is a lot that goes into a well designed greenhouse
including lighting, ventilation, insulating, thermal mass, good
construction techniques... -- this book book gives quantitative advice
on all of these.
Its out of print, but available at Amazon.com used books for about 5
bucks -- quite a bargain!
Thanks for the Amazon tip. I just ordered it. I've read a number of books
on greenhouses, but that was before I really had an opportunity to build