I thought I would make a post about designing for sun management. This was a very important factor when I was designing my pool. I wanted to incorporate the design of the pool with the necessary landscaping to make sure I could have shaded areas in the pool throughout the year and throughout the day.
This seemed to be a completely foreign concept to any of the pool builders I spoke with, so I took matters into my own hands. Maybe some of this could be useful to others starting into the backyard design process.
Step 1: Understand the sun azimuth in your yard
There is a wonderful tool called SunCalc which is a version Google Maps that will show you the compass direction of sunrise, sunset, and the sun at any hour of the day. It also has a relative representation of solar elevation, but not an exact tabular output (we'll get to that).
1a. Go to this link: http://www.suncalc.net/#/33.0123,-96...14.03.28/15:32
1b. Enter your address, click the "satellite" button in upper right, zoom all the way in, and then move the red pin to the exact location in your yard you are interested in.
1c. You'll notice the yellow line points to sunrise, the red line points to sunset, and the orange line points at the actual position of the sun for a given time.
1d. Set the calendar date you are interested in.
1e. You can now enter a specific time of day or click and drag the orange ball on the timeline to "scrub" the sun through the day.
Some useful information:
You'll want to check out the sun angles for different times of year that are important to you (you may or may not care about where the sun rises on Christmas day if your pool is buried under 18" of snow).
The extreme points are December 21 (lowest sun angles) and June 21 (highest sun angles) - all this is for northern hemisphere, btw
The yellow shaded region around your red pin show the full range of elevations and rise set azimuths that location will see through the year just as a handy reference.
In the upper right, there is a box that shows some info for the day you are looking at, Solar Noon is an important one. This is the time where the sun is at its highest elevation on that day.
So theoretically your most extreme sun exposure moment is Solar Noon on June 21.
Step 2: Find the exact sun elevation angle
SunCalc gives a basic idea of relative solar elevation, but for actual shade calculations, you'll want the exact elevation. To get that, you can use the Sun Earth Tools website: http://www.sunearthtools.com/dp/tools/pos_sun.php
2a. Do the same process of orienting the red location pin onto your yard.
2b. Use the pull down menus to select the date and time of interest and click the blue execute button.
2c. Scroll down to the very last table to see the elevation of the sun at different intervals throughout that day (you can set it as small as 10 minute intervals.
This tool can also be set to show shadow lines on the map (hold mouse over box that says "Mode: Sun Path" and select Shadows). I find SunCalc much easier and intuitive to use for that though.
Step 3: Shadow planning
The first two steps give a great idea of the sun conditions of your location, especially SunCalc with it's "scrub" feature where you can easily visualize the sun's position throughout the day, but what you really want to know is "will I have shade in a given spot?" Generally, use the azimuth display in SunCalc to see what direction your shadow will cast and for shadow length, there are two approaches for this:
For existing structures:
3a. Measure or estimate the height of the structure (or use a trick, see below), call this h.
3b. Find your elevation angle for the date and time in question, call this a.
3c. Use the formula below to determine shadow length, L.
Eq 1: L = h / tan a (That is the length of shadow equals height divided by the tangent of the sun elevation angle.)
NOTE: remember this is the length of the shadow on the ground, at the very end of the shadow, only your feet will have shade, your head will be in full sun. Lets say you care about being in the shade while standing up, simply subtract your height, t, from the height of the object that is shading you. So in that case:
Eq 2: L = (h - t) / tan a
How tall is that object?
If you are counting on shade from the top of your roof and you don't know exactly how high it is, you can do some trickeration to find the height.
3d. Measure the length of the shadow your object is casting, this is L.
3e. Enter your address and the exact time and date into Sun Earth Tools.
3f. The exact solar elevation angle will be printed in the data box in the upper left of the Polar and Cartesian sun tracks, us this as a.
3g. Use the formula below to calculate the height of your shading object, h.
Eq 3: h = L x tan a (That is the Height of the object is equal to the length of the shadow multiplied by the tangent of the sun angle.)
How tall of an object do I need?
If you are considering buying shade trees, you can figure out how tall it needs to be to provide shade where you want it.
3h. Determine the conditions you want shade (date/time) and get an elevation angle from Sun Earth Tools, this is a.
3i. Determine distance from where you want shade to where the tree will be planted, this is L.
3j. Calculate the required tree height using Eq 3 (formula directly above this).
Again, don't forget to consider if you want shade at a certain height off the ground. For shading your head sticking out of the water, Eq 3 is fine. If you care about shading people standing on a deck, add that height to the h you get from Eq 3.
How close does the object need to be?
In the case where you determine you want shade on your pool at solar noon on June 21st, you'll quickly find you need a monster sized tree to get it. Those trees cost a mint. The alternative is buy a smaller tree but put it closer to the pool. To figure out how close you should be a tree (or other object) of a known height, h, use Eq 1 and/or Eq 2.
DISCLAIMER: I came up with all this for sizing and locating palm trees, which have a pretty simple shade pattern, a pole with all shade coming from the top. For trees like pines or spruces or something, the shade pattern is totally different. Use these techniques with good judgment in terms of the shade and pattern of the shade. If you do the math and it says you need a 65 foot tall tree, that may be true for a Mexican Fan Palm, but not a Blue Spruce since the shade patterns are wildly different.
Anyway, I thought this may be able to help someone so I wrote it up. Hopefully it is pretty simple and can be used to help you in your planning.