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How do you prevent cold air from entering the house through the inlet and outlet during frigid nights in the winter?

posted Feb 2, 2015, 8:06 AM by Greenhill EnviroTechnologies Inc.
With solar air heating systems, air can be cooled inside the collector when the external temperature is very low and the sun is not shining. If there is an open pathway, some of this cold air might flow into the attached property.

The upper vent is usually unaffected by this issue and normally remains at room temperature. However, the effects of gravity can push the more-dense, cooled air downwards inside the collector. If allowed to flow freely, this air can cool the lower vent and possibly cause a small cool draft to be emitted from the lower vent. In theory, this cooling effect would be no different than the equivalent from a very small glass window, as a collector should be well-insulated, sealed and ideally glazed with insulated material such as twin wall polycarbonate.

To restrict the flow of any drafts, people usually either just cover the outlet at night time, or install a flap over the outlet. Here is a photograph of an example of a flap, you could consider implementing something like this to solve the above problem (if present):

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