How does BTU convert to heat in degrees in a greenhouse?

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SUMMARY

The discussion focuses on the conversion of BTU to heat in a greenhouse, specifically noting that the sun provides approximately 200 BTU per square foot in winter when sunlight is perpendicular to the greenhouse's glass or plastic. Losses occur when sunlight hits at an angle, with steeper angles resulting in greater losses. The average temperature in the greenhouse can rise from 50 degrees to 75 degrees during the day, but it remains at 25 degrees after dark. The discussion suggests building a test model with a thermometer to validate these temperature predictions.

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gary350
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Information online claims sun is 200 btu per sq ft in winter only when sun is perpendicular to plastic or glass of a green house. When sun hits glass or plastic at an angle there are losses. The steeper the angle the more losses will be.

Is it possible to calculate how warm a green house will get in full sun at solar 12 noon.?

Our average day temperature is now about 50 degrees a temperature rise for 25 degrees will make it 75 degrees in a green house tunnel during the day only. It will still get 25 degrees after dark. Winter plants are good down to 0 to -20 degrees but nothing grows below 40 degrees.

If I can prove on paper this will work then i will build it.
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Why not build a test model with some sort of thermometer inside that can be read visually from the outside?

One thing to be aware of is snow or cloud cover may further reduce its effectiveness.

In Texas, we would cover our plants with plankets. However where the plant leaves touched the planket we would see the effects of frost.
 

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