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I'm looking for the best orientation (North-East-South-West) of a greenhouse (simplifiable as a rectangular solid).
My question is more specifically about the sun position effects (over the times of the day and over the days of the year).
With sun effect I mean both solar exposure for plants and temperature increase within the greenhouse. Anyway I think both aspects go hand-in-hand.

Thus, how can I calculate the position of the greenhouse?

PS: if can help to better focus my question, the question could also be re-arranged e.g. for house's rooms: which is the coldest/hottest room in my house?

EDIT: solar exposure's issue was solved. Now it remains how to deal with temperature gain. In short: with maximum solar exposure I will get automatically the higher temperature inside the greenhouse?

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  • $\begingroup$ Have you considered how the planting shelves are oriented inside the greenhouse? What position will give them maximum sun? $\endgroup$
    – Solar Mike
    Commented Dec 3, 2017 at 14:14
  • $\begingroup$ @SolarMike in my mind shelves (or the lines of cantilevered plants) are parallel the longest side of the greenhouse, this for work convenience. And in my mind this parameter is fixed, thus when I say "shelf orientation" I automatically mean the whole greenhouse orientation. If with "maximum sun" you are talking about sun exposure, this is a part of my question. Anyway, I may have to precise what sun effects mean: temperature reached within the greenhouse or the exposure for plants? I think both aspects go hand-in-hand. $\endgroup$
    – mattia.b89
    Commented Dec 3, 2017 at 14:22
  • $\begingroup$ So, what sunshine data are you using? From your latitude and any objects causing shade this should be easy... $\endgroup$
    – Solar Mike
    Commented Dec 3, 2017 at 15:20
  • $\begingroup$ I am starting from a blank paper (excel sheet), please explain what do you mean. $\endgroup$
    – mattia.b89
    Commented Dec 3, 2017 at 16:16
  • $\begingroup$ You should start by finding out where the sun is in the sky each month. $\endgroup$
    – Solar Mike
    Commented Dec 3, 2017 at 16:25

2 Answers 2

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In general: if you are in the northern hemisphere, the sun will pass through the southern part of the sky. Therefore, a greenhouse which is built onto the side of an existing structure will be placed against its south-facing wall so it is not in the shadow of that structure, as it would be if it were affixed to its north-facing wall.

and as pointed out by others in the comment section, for maximum solar gain you want the largest area of the structure facing south as well. So if the greenhouse is rectangular, you want its long axis pointing east-west.

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  • $\begingroup$ powerful answer: short but efficient. Anyway, if I want to do a more precise orientation calculation (e.g. I imagine it depends on my real latitude). Can you point out any book or source? $\endgroup$
    – mattia.b89
    Commented Dec 7, 2017 at 20:29
  • $\begingroup$ you will find plenty written about this on websites dealing with collecting solar energy, but in practical terms you simply want the structure's biggest windows facing due south in the northern hemisphere- latitude doesn't matter. $\endgroup$
    – niels nielsen
    Commented Dec 7, 2017 at 20:33
  • $\begingroup$ I want to share this wonderful site: andrewmarsh.com/apps/staging/sunpath3d.html , it help me deep understand the issue $\endgroup$
    – mattia.b89
    Commented Dec 23, 2017 at 10:04
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The angle will also depend on your objective. I use my green house to winter over various plants so my angle is set to maximize winter light , normal to the sun in mid November/January. If you are growing bedding plants from seed ,you probably want maximum sun in March / April ( northern hemisphere). I found trying to make a variable roof angle was too complicated for a home greenhouse.

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  • $\begingroup$ can you explain the angle of what do you mean? $\endgroup$
    – mattia.b89
    Commented Dec 25, 2017 at 10:32
  • $\begingroup$ The slope of the roof to maximize the sunlight for a particular time period. $\endgroup$
    – blacksmith37
    Commented Dec 27, 2017 at 16:36

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