Although the following was written primarily for North America and Europe it can be adapted to any part of the world where greenhouses are advantageous.
All greenhouses take in solar heat - but this one is unique. It is so well
insulated it needs almost no fuel. Pan-Loks is designing a kit for building
these solar greenhouses of any size. One of the advantages of the Pan-Loks
design is that it is knockdown. If you rent you can take it with you when
you move away. Inquire from STEADI for particulars.
As we attempt to create a sustainable economy that uses less and less fossil
fuel and requires less electric hydropower the need to reorient our priorities
is urgent. The high cost of chemically produced and often chemically poisoned
foods make it even more desirable to turn to home production. Furthermore
the environmental cost of fuel, and the materials and energy to build transport
planes and ships to move food around the world is anti-ecological.
The end result is lower quality food.
A garden at your back door or even in an extension to your house can supply
a wholesome work place, an improved environment and healthy food a few
steps from your door. With a minimum of experience and less work than going
to the market, it will give you fresh tomatoes, lettuce, other fresh vegetables
and fruit all year. One of the most ecological greenhouses is the lean-to
on the south wall of your house. With openings into the house both at
floor level and at the greenhouse roof level you will get a free environmentally
friendly heater. If it also includes heat holding materials it will help heat
your house even on cloudy days thus saving on your house heating costs. And
it gives off a superior atmosphere loaded with fresh oxygen and the fragrance
of growing plants.
Although the design described here is primarily for a greenhouse attached to
your house it will work equally well as a stand alone building. It can
even be large enough to serve as a "tropical tea room" that
will take you on an imaginary trip to Bali on a blustering winter day.
The Solar Greenhouse is unique because it needs almost no extra heating fuel.
One of the highest costs in commercial greenhouses is heating. The large glass
walls and roof lose a lot of heat on cold days and nights especially when the
wind blows. The Solar Greenhouse is designed to reduce this cost by using
a special heat trapping and conserving design.
ORIENTATION MUST BE SOUTH in the northern latitudes. Large buildings, coniferous
trees or any other obstruction that blocks the winter sun will greatly reduce
its effectiveness. Take bearings with the North star or a compass and then look
45 degrees to the east and west of south. If there are no large obstructions
you are well placed to construct a Solar Greenhouse. If you have a larger piece
of land you may be able to choose a hillside sloping south. This
is also desirable because it cuts off the north winds.
THICK WALLS ON THREE SIDES Your solar light and heat will come mostly
through the south windows. Walls facing other directions may lose more heat
then they gain. You are building here a kind of solar box cooker, with vents
of course, so you don't over heat your plants. Walls can be of any
material so long as they have very good insulation. The old New England
ice houses used sawdust. Straw bales are becoming popular. See cob
house building for another kind of thick clay-sand earthen wall. The side
walls may also be light panels like the insulflectors. Whatever
is used it should have no cracks for draughts to push through and no cold spots.
SOUTH SIDE IS SLOPING GLASS The angle of pitch depends on
your latitude. It should be about 15 degrees less than your latitude
since the winter sun will only pass at its lowest angle for a few winter days.
It could also have a versatile wall with a south sloping roof. The roof
will cover the whole length. If it is more convenient there can be some
unglazed roof at the very top because the sun shining through this area will
not help the plants. It would warm your house, however.
The bottom of the south wall will have to be high enough to allow the insulflectors
to swing down far enough to reflect the sun's rays into the middle of the window.
INSULFLECTORS -- are the special part of this design. They close over
the windows to insulate them at night and on very cold dark days. When open
on sunny days they reflects the sun's rays into the greenhouse window.
They may be 8 to 12 inches thick. The underside that comes against
the window is covered with aluminum foil. This may be pasted on to any
thin flat sheet such as 1/8" plywood. The outside is painted or coated
with something that can withstand the weather. Between these two layers is good
insulating material such as straw, sawdust, polystyrene, glass beads,
pumice. A good insolating low price material is dry leaves. Some
calcium carbonate would make a good fire retardant if mixed with the leaves
and good fertilizer when the leaves are taken out and composed. If the
panels will get very hot in your climate, materials should be avoided that will
break when frequently heated. The aluminum foil, will shield them from
some of the heat.
The insulflectors attach to the greenhouse at the top and bottom edge of the
window. Since they will be closed on cold nights and opened the
next morning they should not be too heavy. One possibility would be to
make them in sections . Opening and closing could also be done with ropes
and pulleys.
DOUBLE GLAZED WINDOW. Inside the clear glass or plastic window another
frame can be fitted that is covered with clear plastic to create an insulating
air space This creates a kind of double glazed window. It may be necessary
to arrange something that will blow air between them when they fog up.
Since these frames will be easy to remove, replacing the plastic after a few
years will not be difficult or costly.
LIGHT REFLECTORS To avoid having all the plants lean south
towards the window the ceiling and back wall can be painted white or in some
cases covered with reflective material to draw the plans straight up.
DOORS A larger greenhouse may need a door at each end, otherwise
put the door on the west wall. It should be almost air tight. A little
crack on a windy day can take out a lot of your precious heat. If there
is a door on the east side you may want to add a little vestibule to cut the
wind
TRAPPING THE HEAT- Heavy masonry or earthen walls or containers of water are
all good for storing heat. The solar houses in Davis, CA have large vertical
pipes just inside their solar windows. A fish pond the base of the
solar window could help. Large drums of water are good. Any
place were there are no growing plant beds should have some sort of heat catching
material. If you use the tropical tea room plan the floor should be heavy
masonry that absorbs the heat.
THREE STORY GARDEN Mix low growing plants with medium high plants with
little trees, or shrubs that will shade those that prefer a cooler space.
Create a live tropical forest not a mechanical type environment. Frogs
and toads will help deal with insects if you give them water and don't use refined
chemicals or pesticides. Canaries and parakeets can live freely there,
too. Guinea hens or even smaller fowl will also eat the insects.
Chickens, need to be separated so they can't dig up the seedlings with their
strong feet. They will eat your garbage and give fertilizer back.
COMPOST AS MUCH OF YOUR WASTE AS POSSIBLE, PLANT AND HUMAN - A compost latrine
can be inside. If plenty of soil is used to "flush" each use
it will not smell. Be sure to have plenty of earth to "flush", cover
every defecation thoroughly. The soil not only keeps out the flies and other
insects that can carry infection but it contains the composting bacteria.
Thus when it is full your compost is already built. You can throw weeds in too
to balance the nitrogen/carbon ratio, essential to a good compost. And if you
don't feed your garbage to your birds, put that in too. Cat and dog manure is
so strong it may be better composed elsewhere, however.
The added soil smothers the ammonia and introduces decomposing bacteria.
Have two side by side. Leave one to compost 25 to 30 days while using
the other. This will assure you are putting it on your garden only well
processed material purified by the bacteria. Even then it is best not
to put it near leaves like lettuce that will be eaten raw.
This system is, of course, is dangerous when misused because human excrement
harbors human pathogens. When done right, however, it is an excellent
recycler of many of the nutriments the growing plants need.
Build it by digging down about 3 feet. If the soil is gravely or
sandy it should be lined so the dangerous
VENTS are essential to regulate the flow of air. The greenhouse will be more
humid than the house but if the air circulates enough it will reduce or eliminate
the destructive fungus growths. Don't spray with poisons. Soap sprays that aren't
poisonous can be effective. Proper venting is also important if you are using
it year around. It may even be desirable to build a chimney or just add a metal
chimney exhaust pipe at both ends of the peak to draw out the hot air in summer.
Paint the pipe black. As it takes up the heats in the sun the hot air
inside will rise like in a stove chimney and give you a free solar fan. Be sure
the vents into the greenhouse can close tight and open easily. In the
winter air the greenhouse regularly in the middle of the day. A quick change
of air will help discourage the fungi and restore fresh air. If the air is changed
quickly the heat stored in all the walls and floor and other things will bring
everything back to temperature before any damage is done.
ENJOY - Make space for enjoying it, sun bathing on a cold day, having
a tea party or just sitting and listening to music or reading. A solarium does
not need a large space. A plant thronging area can be more revitalizing than
a large room.
BECOME MASTER OF YOUR FOOD SOURCE. More and more people are realizing that a
good wholesome vegetarian diet brings health and a longer, disease-free life.
Your solar greenhouse can replace hundreds of doctor's visits, give your children
a whole new view of life with living things close free you from contributing
to the degradation of our land and food sources. If many families had all year
food growing spaces it could revolutionize our world food supply our world economy.
But don't tell your grocer or your stock rancher or agribusiness friend.
ONE LAST WORD - You are getting this study of many years free. Will you kindly
thank us for it by doing one little thing. Email us at owl@steadi.org
and tell us how yours worked. If you give us your phone number we'll call
you back so we can chat briefly about your experience and add your new knowledge
to ours.