INTRODUCTION 7<br > First， a definition is in order because there is some confusion created by the term solar greenhouse."<br >The confusion is understandable because all greenhouses are， in fact， solar. However， traditionally<br >designed greenhouses have rarely been concerned with the most effective use of the sun s energy. Those<br >described in this book are. We have incorporated four basic elements in the design and operation of each of<br >our greenhouses: ，<br > 1. The most efficient collection of solar energy.<br > 2. The storage of solar energy.<br > 3. The reduction of heat loss during and following collection periods.<br > 4. Zone layout for the particular light and temperature requirements of various plants.<br > Attention to these elements produces the following benefits:<br > 1. Surplus thermal energy produced in winter can be used immediately in an adjoining struc-<br > ture or stored for later use.<br > 2. Independence from mechanical heating and cooling devices powered by fossil fuel.<br > 3. Fresh food and colorful flowers right through the winter.<br > This book， the designs and the benefits derived from it， all come from a basic concern with people s<br >relationship to their environment. One basic environmental problem is centered around misuse of energy.<br >We realized that while many people wish for altemative systems， the success of such systems is dependent<br >on the individual s commitment to the system coupled with an understanding of what makes it work. And<br >，we want you to know exactly what s involved in building and maintaining your own solar unit.<br > In the following pages， we ve shown methods that can be used to make an appreciable addition to the<br >quality of your life through a closer involvement with your food chain (fresher and cheaper vegetables)， a<br >.free source of partial heating for your house， a more realistic integration with the cycles of the sun， the<br >seasons and the weather， and independence from corporate energy and food games. Whether or not you<br >aetually build a greenhouse depends on many factors: space， economics， appropriateness to your location，<br >and determination， to name a few. But even if you don t build， reading this book will enlarge your<br >understanding of your environment and your relationship with it.<br > This book grew out of the Solar Sustenance Project begun in 1974. It was a modest demonstration<br >project to determine if attached greenhouses could supplement homes in eleven high-elevation locations in<br >the Rockies with fresh food and heat throughout long and cold winters. The work has evolved into an<br >educational process that has worldwide relevance. The solar greenhouse is unique in that it can satisfy two<br >basic human needs， food and shelter. With other beneficial side effects， such as water conservation and<br >distillation， the potential for greenhouse application is just beginning to be understood.<br > When we began the project， many engineers and architects insisted that our simple greenhouses<br >wouldn t lengthen the growing season even a week. We were told by others that the 90-degree heat<br >produced by the units was virtually useless. Fortunately， we didn t listen to them. Balancing the<br >negativism of the cynics， we had the support of many people in the field: Keith Haggard and Peter Van<br >Dresser of Santa Fe， T.A. Lawand of the Brace Institute in Quebec， Dr. Francis Wessling of the University<br >of New Mexico， and several of the people mentioned in Chapter VIII. Now， competent professionals from<br >all over the world are eagerly exploring the solar greenhouse field， and their expertise will certainly<br >advance the state of the art.<br > An important aspect of solar greenhouses is that the principles of design can be applied at any<br >economic level. The $7.00 recycled lumber and polyethylene greenhouse slapped to the south side of a<br >