A solar greenhouse attached to the south side of a house can reduce heating bills, add a sunny area to escape from long, bleak winters and also extend the growing season for edible plant products like hot house tomatoes. This kind of addition is called a retrofit.
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GREENHOUSES are not designed to store, and conserve heat, but they do
provide a way to jump start seedlings and extend the growing season at minimal cost.
Inexpensive polyethylene plastic stretched over a
network of steel polls is the kind of investment commercial growers like. If
they get a few years from a sheet of plastic they're happy. Special UV
protected plastic helps to increase the life span of thin plastic films and
double layered films pumped with air are used in cold climates, but few home
owners would be happy with this temporary greenhouse.
Home made stand alone greenhouses don't have to be expensive as long as the plastic glazing is changed from time to time.
FREE STANDING
SOLAR
GREENHOUSES are more energy efficient than the commercial greenhouses, but
they tend to be more expensive and require more planning. The south side is
glazed and the the north foundation wall is insulated on the outside to prevent heat loss. Thermal shades
may be used on the inside of the glazing to retain heat during cold winter
evenings. Containers of water are often stacked against the walls to store heat
and moderate temperature swings. Without a heat
storage system, or thermal shading system a greenhouse could experience
extreme temperature fluctuations.
ATTACHED SOLAR
GREENHOUSES are versatile. They can be designed to favor home heating or plant growth or both. An attached solar
greenhouse should be isolated from a dwelling to provide a net home heat gain. Storing heat inside the greenhouse will moderate temperature
swings, but don’t expect to heat your house and also keep your
greenhouse warm at night.
Oh
No!
What about my plants? Won’t they freeze at night when it gets cold?
They might. That’s why you have to decide what you want to do. Do you want to
heat your house or grow plants? In a mild climate like
How
about a cold climate like
You could do
the same thing in
There are a number of kits
available, but weather you purchase a kit or build it from scratch you should
have an understanding of greenhouse thermodynamics.
Should
I build an active or passive solar greenhouse? Somebody told me that passive is
better because no electricity is wasted with fans and pumps to transfer heat.
It’s up to you but generally speaking passive solar greenhouses are best suited for mild climates with a plentiful supply of sunlight and active systems are needed in cold climates with limited sunlight.
How
about style? Should I have go with diagonal or vertical glazing?
Well they both have their
advantages and disadvantages.
Diagonal glazing has the most heat gain and it’s also advantageous for plant
growth unless you like your plants to grow sideways.
Actually vertical glazing could work in cold climates where a winter sun would
be almost perpendicular to the glazing. Vertically glazed surfaces also loose
less heat than diagonal surfaces.
This
is very interesting and my wife and I are very excited about having a solar
greenhouse but I have to ask you can a solar greenhouse meet the heating needs
of my home?
Well this will of course
will depend on your heating needs and the heating needs of your home and family
and how much you're willing to spend. If you
live in a mild climate or if you can tolerate extreme temperature swings a solar
greenhouse could help you get through a nasty winter, but if your wife is not
happy with the heating situation you might wind
up on the front lawn in a snow drift. A solar greenhouse is only one part of a
well panned energy independent solar heated home.
A solar greenhouse should be more than a method of heating a house. A south facing solar thermal roof integrated into a home heating system with PV panels, a solar greenhouse and a wood stove back up could provide the conditions necessary for energy independent housing. Perhaps energy independence is not important today but it may become important in the future in a world without oil.
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