losses are proportional to the surface area of the greenhouse,
the heat transfer coefficient of the greenhouse material and the
perimeter, and the difference between inside and outside
temperature.
 Infiltration is the exchange of inside and outside air. The
rate of infiltration depends upon the direction and the speed of
the wind, the difference between inside and outside temperature,
and the type and quality of the greenhouse construction.

 Technical Notes

 A practical method to compute the total heat losses from a
greenhouse is to add the conduction and infiltration heat losses.
 Conduction heat losses can be computed using the conduction
heat transfer equation.
 Qc = A U Dt (1)
where
 Qc = Heat transfer through the material in BTU/hr,
 A = Exposed surface area in ft2,
 U = Heat transmission coefficient in BTU/hr F ft2,
 Dt = Temperature difference between inside and outside
 in degrees Fahrenheit.

 Infiltration heat losses can be computed using the formula:

 Qa = 0.02 Dt V Na (2)
 where
 Qa = Air infiltration heat losses in BTU/hr,
 Dt = Temperature difference between inside and outside
 in degrees Fahrenheit,
 V = Volume of the greenhouse in ft3, and
 Na = Number of air volumes exchanged per hour.

 Total heat losses from the greenhouse are obtained by
 summing conduction and infiltration heat losses.
 Qt = Qc + Qa (3)
 where
 Qt = total heat losses in BTU/hr.
 Sample Run

 The following is a step-by-step example of how to use this
 software to estimate the heat losses from different greenhouse
 types.

 1. To run the program place the disk that contains the
 GREENHOUSE.COM file in Drive A.