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Old 03-24-12, 11:57 PM   #5
briligg
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I think that because the NRC data was really meant for photovoltaics, when they say 'insolation' they don't mean the same thing as what someone working on passive solar heating means. Maybe they count a cloudy day as one in which 15% of the sun's energy is still available for harvesting, so it is still a plus. But for passive solar, a cloudy day that is also cold is a net loss. The remaining solar radiation has virtually no heating value. So i'm going to use the ASHRAE data.
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