| Ventilation Use a ventilation system to automatically protect your greenhouse plants
from withering heat build-up. No need to daily open and close vents, trying
to out-guess the weatherman! Let a thermostatically controlled system do
all the work. The thermostat turns the system on at the temperature you
select. The fan expels hot air and fresh, cool air is drawn in through the
shutters. A fan speed control enables you to adjust the amount of air flow
to suit the seasons. A motorized shutter is wide open when on and held closed
when off. Select one of our ventilation systems or build your own
system from components. Caution:
A fan system alone cannot completely cool a greenhouse. Shading is also
required. Additional cooling is possible with a misting system or evaporative
cooler.
Shading Install shading to shield the greenhouse or sunroom between 9 a.m. and 5
p.m. Severe western exposure may require shading until 7 p.m. Shading should
cover the roof and at least the upper half of the south wall. The amount
of shading needed varies depending on your local climate, greenhouse design,
and light requirements of your particular plants. Use the least amount of
shading necessary, because excessive shading can slow plant growth or cause
plants to “reach” for more light. Misting Ventilation and shading will prevent the greenhouse from seriously overheating,
but it is evaporation of moisture inside the greenhouse that will actually
maintain a comfortable temperature. Evaporating water soaks up heat like
a sponge, because heat is used when water changes from a liquid to a gaseous
form. Good air circulation from fans increases evaporation. The amount of
moisture necessary to cool the greenhouse will vary considerably depending
on the amount of ventilation and shading provided, your local climate, and
daily weather changes. | 
