SolarAttic PCS1, User Manual

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SECTION 2 - HEATING DATA Page S2-12
VENTILATION
Attics get very hot. In some cases, attics get extremely hot. All of this occurs
because of solar radiation. Homeowners have taken extraordinary steps to cool
down their attics. These steps have included wind driven turbines, roof mounted
power driven turbines, whole house ventilating fans mounted in the attic and
numerous other devices. Creative designs and modifications of houses have
produced cooler attics in certain instances.
Required passive ventilation needs [for moisture purposes] use the rule of
thumb of 1 square foot for every 350 sq ft of attic space when a poor vapor barrier is
present on the ceiling of the home. When a good vapor barrier is present, as in new
home construction, the rule of thumb is 1 square foot for every 700 sq ft of attic
space. Any ventilation over this amount is ÒadditionalÓ and is added for ÒcoolingÓ
purposes.
Altering a Òcooled-downÓ attic is simple. Just turn off the wind ventilators,
power ventilators and plug up some of the added ventilation holes. Ventilation can
be reduced down to 1 square foot for every 350 sq ft of attic space without much
concern.
Certain types of passive ventilation can actually improve the heat transfer
characteristics of the PCS1. We know that the PCS1 works fine with twice the
passive ventilation that a home was designed with 15 or more years ago. We know
that newer homes are being built today with more passive ventilation. We also
know that power ventilators and wind turbines take out too much heat. The ideal
ventilation for the PCS1 has not been fully defined by research yet.