Fan Shutter Heat Loss is Significant
Tuesday, 04 October 2011 10:32
Did you ever consider how much heat loss there is through fan and intake shutters?
Heat loss through a shutter occurs by conduction through the metal or plastic and by air exchange (infiltration) through the cracks between the blades. If the shutter closes tightly, then most of the loss is by conduction. If the blades are bent or if the hinges are sticky, then infiltration can be the greatest loss. I have seen shutters that were open during the winter with gaps as wide as 1”.
Check operation of the shutters before the winter heating season. Lubricate bearings, check that blades are straight and close evenly and caulk around the frame. Also make sure that the shutter motors are working properly.
When selecting fans, choose those with the shutter on the inside wall as this isolates the fan and housing outside the greenhouse. There is considerable sheet metal housing that is exposed to the cold when the shutter is located outside the fan.
John Bartok, Agricultural Engineer, calculated an example of heat loss through fan shutters which used 2.4 gallons of fuel oil over 24 hours.
For more information including small budget and large budget solutions, see John Bartok's, fact sheet: Fan Shutter Heat Loss is Significant
