- The passive solar greenhouse design allows you to garden year round
without additional heating and cooling systems and costs.
- This greenhouse design has performed well under difficult weather
conditions, including extreme temperature fluctuations, a somewhat
cloudy winter, severe drought with high winds and very low humidity,
and a fairly cloudy summer.
- Without the nighttime glazing wall removable insulation, the greenhouse
did not freeze when temperatures dropped to -13F. With the use of
glazing wall insulation, the greenhouse will remain above freezing
under much more severe winter conditions.
- The greenhouse air may reach freezing temperatures under certain
combinations of cloudiness followed by extreme cold during the winter.
However, if you are growing frost-tolerant plants and/or using row
covers, vegetable growth and production will continue uninterrupted
throughout the winter.
- Soil temperatures never dropped below 50F. Various cold-season plants
come to maturity, produced food, even germinated and grew from seed
all late fall and winter.
- The cost to build this passive solar greenhouse is comparable to
home greenhouse kits on the market. These kits usually presuppose
that you are not going to use the greenhouse during the winter. A
few only allow winter use with an additional heating system, however,
since they lack an insulated foundation, heating costs would be high.
- Season extension systems I have tried were unable to give me the
range and flexibility I desired, were too labor intensive, and were
not durable, long-term solutions. I would not eat a ripe red bell
pepper and certainly could not enjoy a ripe tomato at Thanksgiving.
- After researching many of the passive solar greenhouses written
about in the 1970s-including greenhouses built and operating year
round in Arizona, Massachusetts, Washington, Pennsylvania, Wisconsin,
California and New York-I designed a passive solar greenhouse that
is adaptable for growing all year in a wide range of climates.
- Below is more technical information concerning the performance of
Why Build the
Passive Solar Greenhouse
The building process
How to order
The Technical Details
The average humidity between 9/1/99 and 7/1/00, was 57 percent. During
the winter, a time when humidity can be low in greenhouses, the average
was 62 percent. The solar fan was hooked up on 11/16/99 and the water
wall was only half finished until 12/18/99, four days after the low
of -13F. The shade cloth was fully employed from 9/1/99 through 1/25/00
and then rolled up. The lower two-thirds were put up on 6/3/00. On February
3, 2000, the temperature in the top white plastic five gallon bucket
at 4:30 p.m. was 75F. The temperature in the back metal pail was 88F.
The next morning at 9 a.m., the temperature in the plastic bucket was
63F and in the metal pail it was 65F. Obviously, the metal pails store
and release more heat.
The "shade line" reached two feet into the north bed by 5/9/00 and came to a maximum of three feet into the north bed on the solstice. However, pole beans, lettuce, cucumbers, zucchini, and tomatoes are growing and producing well in the shady area.
On the following graph, soil temperatures were the same in both the north and south beds until early May when I began to track them separately due to the shading of the north bed. The south bed is warm enough for melons and okra. Both bedsí tomatoes, peppers and zucchini are growing well; both bedsí eggplant is a little slow. Where the south bed would be much too hot for lettuce, heat tolerant varieties are producing well in the north bed.
The solar vent opens mechanically by itself with increasing heat and
closes when temperature drops.
The passive solar greenhouse on a winter day.
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