Greenhouses are used to provide the ideal micro-climates for some useful plants & processes (eg. to start off seedlings).
Here are some resources, also see the open source ecology page.
& a legend in greenhouses:
Learn how an eastern New Mexico gardener constructed a greenhouse from recycled materials.
From the Southwest Yard & Garden series.
Vegetable Garden Construction by Jeff from Kentucky of an inexpensive mini green house to start you seedlings in the winter. Visit The Bayou Gardener in Avoyelles Parish Louisiana - Cajun Country at http://www.thebayougardener.com
all greenhouses really are 'passive solar'..
experimental