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View Full Version : Real Life Shadow Calculations - anyone?

tilt
10-21-2011, 04:10 AM
So, post number 4000 - and I think I'll use it for asking for help with a personal problem. There are some mad skills in this guild and almost always somebody who knows the answer to any question. So I pose this question. Can anyone help me calculating the shadow impact of raising the roof on my house? :)
I've attached a picture of the land plot with the house on it, measurements showing how high over sea level the ground is, where it is in the world, how high the roof is and how high I'd like it to be.
I am of course aware that the shadows cast by the house will change depending on time of year.

What I'm really curios about is how far the shadows reach now and if the roof gets raised, what the difference is - and if it will impact my neighbor (cause I'm a nice guy *lol*). I have no idea how to approach this, but I guess somehow it should be possible to get some angles of the sun and such. If I could map it in 3D I would - but that is beyond my capabilities.

Hope someone can help :)

Fransie
10-21-2011, 05:50 AM
You can calculate the sun angle of any given time and date on any location here (http://solarelectricityhandbook.com/solar-angle-calculator.html). Then it's just a matter of high school trigonometrie.

It's a lot easier to check it out in Google Sketchup. I've drawn the basic shape of your house (old and new) for you, all you need to do is play around with the shadow settings - time and date, and you can watch the shadows move.

The height above sea level doesn't make much of a difference, but the slight slope does. Haven't modeled this though.

And I sincerely hope your house looks better in real life than my model.

Frans
39375

Sketchup file here: 39374

tilt
10-21-2011, 06:09 AM
Niiiice, thanks :) ... the angle of the roof will actually be close to the same, as I want to raise the walls as well, but that shouldn't really make much difference since the top will be at the same height.
My town wasn't on the list, but I picked one half an hour (30 km) north from here.
Malmoe
Optimum Tilt of Solar Panels by Month

Figures shown in degrees from vertical

Jan
Feb
Mar
Apr
May
Jun

18°

26°

34°

42°

50°

58°

Jul
Aug
Sep
Oct
Nov
Dec

50°

42°

34°

26°

18°

10°

So I'm guessing these numbers of the tilt of the solar panel corresponds to the angle of the sun (ie the same angle)?
Also, the angle is when the sun is at its highest, right?
So now I "just" have to learn how to make/move the sun in sketchup (and measure angles in there) :)

Fransie
10-21-2011, 06:22 AM
I *think* you're right about the angles. You don't need the angles in Sketchup though. There's a slider for month and a slider for the time of day in the Shadows Settings (Window -> Shadow). Just set these to the required setting and use the Tape Measure Tool (T, or Tools -> Tape Measure) to measure where the shadow ends. Or just guess it a bit, there are enough reference points on your drawing.

39377

You can actually put a picture from Google Maps under the house, but I obviously do not know your address, and Trelleborg was too large to search for a house with these precise specifications :)

Lukc
10-21-2011, 07:33 AM
I was going to say: SKETCHUP! But Fransie beat me to it and did all the work as well :D Thumbs up Fransie.

Fransie
10-21-2011, 07:37 AM
New files: 39379

As described in private message.

tilt
10-21-2011, 07:56 AM
thanks Fransie for making these, those are very cool :)

tilt
10-21-2011, 07:58 AM
and here a rep-slam +15 for your help :)

Ascension
10-23-2011, 10:43 AM
Yep, way to go fransie. I was gonna say the same thing.

tilt
10-24-2011, 03:34 AM
Just wanted to say that I showed the houses/shadows to my wife and she thought it was really cool too.. thanks again Fransie, so now when I get some time, I'll try to mess around a little more and add a hedge, a shed and some small trees :)

Fransie
10-24-2011, 09:54 AM
You're welcome. But showing it to your wife is one thing, the real question is whether your neighbours will think it's cool too... :)

tilt
10-24-2011, 05:18 PM
yep, that is the real test ;)