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Name: David
Status: educator
Grade: 9-12
Location: Outside U.S.
Country: USA
Date: Spring 2013


Question:
Is it possible to build a building (greenhouse) that will gain more sun heat than is lost at night on a sustained basis? ( northern winters)



Replies:
Hi David,

The answer to your question depends on a number of criteria that you have not stated, such as..... how cold does it get at night? How warm does it get during the day? How far north is "north"? Importantly, latitude dictates how long your day is versus your night.

Generally speaking the answer is yes. Assuming you are located at a "reasonable" latitude (not within the Arctic Circle, for example, where night lasts 6 months), and it is not "unreasonably" cold, it is indeed possible to build a greenhouse that will "gain more sun heat than is lost at night". But that may not be good enough for you.

Your phrase, to "gain more sun heat than is lost at night", is rather vague and hard to define. In such a situation, the average inside temperature will of course initially start to rise. But as the average inside temperature rises, more heat will be lost at night because the difference in inside versus outside temperature will increase. The result will be greater heat loss at night.

Eventually, an inside temperature will be reached where solar heat gain will equal night time heat loss, and the average inside temperature will reach an equilibrium and rise no further.

So your real question should not be "can a greenhouse be designed to gain more sun heat than is lost at night". Instead, your question should be "can a greenhouse be designed that will, when exposed to defined environmental conditions (that you must state), maintain a specified average inside temperature.

Regards, Bob Wilson



Hi David,

Thanks for the question. Yes, it is possible to build a greenhouse that will gain more solar heat than is lost at night. One possible greenhouse would have solar panels, a circulating fluid to store the heat, insulation, and perhaps movable solar panels. I will leave the details up to your imagination, but it is quite possible. I would look into the EPA web sites or LEED web sites for details.

I hope this helps. Please let me know if you have more questions. Thanks Jeff Grell



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