permaculture

[YankeePerm@aol.com]

In a message dated 11/5/97 8:31:15 AM, chusby@vt.edu wrote:

>Dear fellow Permaculture List members,
>
>       I am very interested in the passive solar greenhouse concept.  I
>would like to learn more about how to design such greenhouses in light of
>permaculture principles.  I am especially interested in the design of solar
>greenhouses for colder climates such as Northern Michigan.
>
>       Where can I find reliable information about solar greenhouses from
>a permaculture perspective?
>
>Thank you for your help.
>
>Chad Husby

Hi Chad:

We have a number of designs done as part of permaculture designs for Northern
(Northern Hemisphere) climates ranging from high winds with heavy winter
cloud cover and -40 degrees temp in Northern Ontario to a suburban attached
greenhouse in Central Massachusetts.  These are listed in our Special Order
Catalog.

Generally, the best book on the subject is also about the least exepnsive:
"Low Cost Passive Solar Greenhouses" or something quite like that by NCAT
(National Center for Appropriate Technology, POB 3838, Butte MT 59701--I'm 90
percent that the address is correct, but it is from memory).  

Northern Michigan doesn't mean much in terms of basic design parameters.  Do
you mean Upper Penninsula, which is upwind of the Lakes and likely to have
clear winters, at least compared to northern Lower Penninsula, which far more
likely to have more cloud cover.  Cloud cover affects a number of
permaculture/solar design factors, including the pitch of glazing, proportion
of main building heat that can be harvested from such a greenhouse, amount of
thermal mass storage you want to design in, potential uses of the greenhouse
itself, including crop selection, etc. Generally speaking, solar greenhouse
design has been worked out pretty well and there are only a few flaws in the
conventional wisdom.  For example, contrary to conventional wisdom, thermal
mass DOES NOT have to be in direct sun to be effective in a solar greenhouse.
 This is because of phase change energy transfer due to condensation during
the day on the relatively cool shaded thermal mass and the fact that
greenhouses carry more moisture than other portions of the dwelling unit.
 (This effect is most useful if water is used for the thermal mass in the
form of 55 US gal drums, which by a blissful accident are the perfect size
and proportions to temper diurnal temperature flux when filled with water.)
 Latitude effects are also important--at some latitude, there isn't enough
day in winter to bother running the greenhouse as anything more than a fancy
wood shed, but it has important horticultural uses in other seasons. 

In general, I encourage my students to design buffer structures in
cold-winter climates, meaning that the heated building, besides being
insulated and containing as much thermal mass as practical of two or three
sorts also has all outbuildings attached, particularly on exposed sides
(usually North and West) to buffer the effects of wind and cold.  Attached
solar greenhouses serve this function even on the south side (Northern
Hemisphere) where they belong.

One final tip, be sure to locate any chimneys so that they are in the solar
greenhouse.  The warmer the chimney, the more efficient, particularly when
you start a wood fire.  When the wood stove is cranking, presumably mostly at
night and during cloudy periods, the chimney gets warm and the solar
greenhouse keeps it way warmer than exposure to -F temperatures at the same
time benefiting from the heat that the chimney does use.

In general, in designing thermal systems 1) integrate like your life depends
upon it, and 2) remember that heat doesn't get used up when used.  If you
cook with heat, the same amount of heat is still in the building.  So
integrated systems should be good at absorbing heat from one another,
shunting heat around, and using it as often as possible.  For example you
have your house with an attached solar greenhouse and attached to the
kneewall of your solar greenhouse should be your cold-frame hotbed.  Each
gives you options for heat transfer and each uses heat escaped from the
others. 

For Mother Earth, Dan Hemenway, Yankee Permaculture Publications (since
1982), Elfin Permaculture workshops, lectures, Permaculture Design Courses,
consulting and permaculture designs (since 1981), and now correspondence
courses via email.  Next live training:  Paraguay, Sept. 1998. Internships
available. Copyright, 1997, Dan & Cynthia Hemenway, P.O. Box 52, Sparr FL
32192 USA  YankeePerm@aol.com  

We don't have time to rush.