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Heating
Your Greenhouse for Four-Season Growing!
What you can
grow in your greenhouse is only limited by how warm your heat is. First, select an energy source.
Electric heaters are generally less expensive to purchase and work well if you have electricity
wired to your site (no unsafe extension cords, please!) Gas heaters use either natural gas or
propane. They are inexpensive to operate and require no electricity.
Next, decide
how warm you will need to keep your greenhouse. If your goal is to winter-over plants, you need only
keep your greenhouse above freezing. If you plan to get an early start with seedlings, you will need
a more consistent and constant heat supply.
Heaters are
rated by the amount of BTU's (British Thermal Units) they produce. In order to determine the correct
size of heater you'll need, you'll first need to gather some information on the size of your
greenhouse, the minimum outside temperature you expect for your area, and the minimum temperature
you want to maintain in your greenhouse.
Greenhouse
BTU Calculator
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Do this |
Formula
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Example
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Determine the total square feet of exposed surface
area of your greenhouse. |
288
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Nine sheets of corrugated plastic (4' x 8' sheet)
would be 9 x 32 = 288 s.f. |
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Determine the maximum inside temperature you want to
keep your greenhouse. |
60
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You're growing seedlings, so you want the inside
temperature to stay at 60 degrees F. |
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Determine the minimum outside temperature you expect
for your area. |
20
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You live in Oregon and you expect temperatures to be
down to 20 degrees F this winter. |
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Determine the heat loss factor for the greenhouse
covering material |
.8
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Corrugated plastic has a heat loss value of .8. |
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Multiply the square footage by the difference in
temperatures, then by the heat loss factor. |
288
x 40 x .8 = 9216
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The total square footage of the covering surface
area is 288. The temperature difference is 40
degrees F. The heat loss factor is .8 |
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9,216 is the minimum BTU rating to keep your
greenhouse at the desired temperature during the
coldest time of the year. To view all of our
greenhouse heaters
CLICK HERE ► |
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