How can I work out which parts of my yard are sunny?

April 10, 2006 3:34 AM

I'm looking for an app that will calculate how much sun different parts of my yard get over the year.

We've got a trapezoidal suburban block that slopes. Obviously, there's a house on the block as well. Is there an app that'll let me see which parts of the yard are the sunniest, and which are only sunny for part of the day, or in shadow for much of the time? An app that could, say, let me enter the lat, long and elevation of the four corners of the yard, drop a house in the middle of the yard, calculate the position of the sun from day to day, and tell me which parts of the plane get good light, and which get bad light in a graphical fashion (for example, by highlighting sunny parts white, through yellow, orange, red, blue, black etc)? Man, it's a big ask when I write it all out! Any other ideas for mapping this out reasonably quickly?

posted by obiwanwasabi to Science & Nature (7 answers total)

That seems like a tall order, personally I'd grab a few beverages, a bbq, some bratwurst or chicken, and spend a day in the yard. You can probably tell which areas are the most exposed to sun throughout the year by how well grass and other things are growing in different parts.
posted by efalk at 3:51 AM on April 10, 2006

You could download a demo of Sketchup and its tutorials, then model your house and yard. It lets you enter your lat./long., time of day, and cast shadows (since these things are important to architects who want to take advantage of passive heating/lighting). It wouldn't particularly 'grade' the various areas.

On preview: as much fun as Sketchup can be to use, I think efalk probably has the right idea.
posted by kimota at 3:58 AM on April 10, 2006

See also this previous thread.
posted by cerbous at 4:37 AM on April 10, 2006

Sketchup 5 lets you grade if you have contours, and will do sun analysis, though not summing it over days/hours, you'd have to update it by hand and take representative snapshots.
3dsMax will do the same, but it's harder to use and more expensive.
Ecotect will do all the above, plus output pretty graphs of total solar gain during the year, solar animations, etc., and is dead simple to use.
posted by signal at 5:59 AM on April 10, 2006

Another thing:I'm swamped with work right now, but if you haven't sorted this out around the end of the week, send me an email with the data you have and I'll do the analysis for you.
posted by signal at 6:10 AM on April 10, 2006

you know how far away the sun is. You know how large the objects are that create shadows.

then it is just a few related rates problems: relate area of shadows to the angle of the sun. Classic Calc I problem.

then you can figure out exactly how much of your yard is exposed to sun at any given time (t).

this is probably far more involved than im making it out to be, but my way is much more fun.

if you really wanted to get clever you can plug all the data you get from above into something like MATALAB and do some gradient mapping to get a good idea of what things are sunny and when.
posted by I_am_jesus at 7:51 AM on April 10, 2006

Response by poster: I see a link in the previous thread to something called a Solar Pathfinder that appeals to my inner gadget freak. It'd make a nice community resource, too (for loaning to, say, local organic growers groups). Thanks for the generous offer, signal - I may call on you yet!
posted by obiwanwasabi at 4:48 PM on April 10, 2006