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The Sun's effect on design

When dealing with the summer sun, let's say in Tennessee and the typical 2 story, peaked, atrium, window wall facing south, how much overhang do you need to keep the sun out of the room? Since it may not be feasable to completely keep it out, what would be a reasonable compromise distance?

Is it actually better to face a windowed wall home slightly Southeast in the midstate areas to avoid too much sun in the summer especially in the afternoon?

If you wanted to take advantage of possibly some solar, radiant heat in the winter by using stone or slate flooring for a distance of 4 to 5 feet inside of this glass wall, how thick would the material used have to be to really have an reasonable effect as a heat sink.

Thanks,
Joe

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Comment by Joe Volpe on April 21, 2009 at 4:58pm: Jeremy,
Good point. My two experiences in life have been in Mi and Fl. but hope one day to build or buy in TN. I have noticed the extreme glare in photos of homes facing south in TN if they have the atrium window wall. I'm begining to draw the conclusion that a slight rotation to the SE would be the best for the morning sun. This would also be more cheerful in the winter. Here in Fl you can't sit outback if your home faces West as you broil to death and it's necessary to pull the shades on the windows or run your A/C bill out of sight. We experienced FL home owners chuckle at the people who come down and buy homes on the Gulf thinking of those beautiful sunsets not realizing it becomes a nightmare most of the year.

The trees are great sunshades as you mentioned if they conflict with the planned lake view. Down here in Fl they really cut the temperature down drastically when in the shade of them.

Thanks
Joe

Comment by Jeremy Bonin, AIA NCARB LEED AP on April 21, 2009 at 10:29am: Hello Joe,
Pilkington also has a Sun Angle Calculator that works very well, you do have to purchase it though, i believe it was $25. As for west facing glass gable walls, yes they are very dificult to shade appropriately - depending on your geograhy and site don't dismiss mother natures seasonal shading devices, decidous trees. In addition, if your gable wall also happens to be lakeside, you need to consider the solar gain you will recive from reflected sunlight UP into the home, and overhangs do not help in that case typically.

Comment by Joe Volpe on April 9, 2009 at 3:47pm: Now it makes sense. It also clearly points out why a West facing window wall is not very desirable in sunny climates such as here if Florida.
Joe

Comment by Jake Lappan on April 9, 2009 at 3:38pm: you cross the time (red line) with the month (blue line) and take it horizontally to the left to get your sun angle (as if it perpendicular to the wall). it wont be exactly correct b/c the sun wont be perpendicular to the glass as it rolls around the sky (thats the azimuth angle, but dont worry about it). so if you want to block the sun in summer time between noon and 3 pm you would go up to "june 21" look where it hits "12 PM" and the angle looks to be approx 76 deg. and at 3 pm it is 50 deg. Design your over hangs for those angles and or what ever times you want for the summer months.

Comment by Joe Volpe on April 9, 2009 at 3:29pm: Mike,
Nothing to do with this discussion but I am unable to get direct messages through to members such as yourself or Neighborhood. I hit send and it does nothing. I don't know if it is an overloaded AOL down here in Florida or something is blocking it as it previously worked. This problem started a week ago on both blogs.
Joe

Comment by Joe Volpe on April 9, 2009 at 3:26pm: Jake,
Yes, and I don't understand how to interpret this.
Joe

Comment by Jake Lappan on April 9, 2009 at 3:22pm: is this what you got?

Comment by Joe Volpe on April 9, 2009 at 3:11pm: Jake
I tried the program that you suggested and the result didn't make sense to me when I put in the parameters for New Tazewell, TN but meanwhile I ran some calculations. The summer angle for Taz is 23 degrees which approximately splits a 45 degree angle. So what this means is that you have a 2 to 1 ratio. Go up 10 feet and you have to go out 5 feet to put the shadow at the foot of the wall. Go up 20 feet and you need a 10 foot overhang which becomes a roof over a porch to make it look good. It also says I would have to have second thoughts about putting rock or slate near that window as it could create unwanted heat in the summer without the right overhang. All of this is crude because of the effects of reflectivity of the glass and type of glass used. I used to own a flat roof house in Mi with a 12 foot window wall and a 4 foot overhang and it worked pretty good. A little sun in the summer but lots of solar heating in the winter when the sun occassionally shined. When I saw a lot of log and timber frame homes with atriums and prow fronts I got to thinking about the sun blasting in.
Thanks again,
Joe

Comment by Joe Volpe on April 9, 2009 at 2:31pm: This is going to get interesting as I play with these. I read the website that Amy suggested and it mentioned Sun angle summer solstice so I went hunting and found the following:
http://cwx.prenhall.com/bookbind/pubbooks/lutgens3/medialib/earthsun/earthsun.html
It allowed me to plug in the latituce for New Tazewell, TN and it gave me a 23 degree angle for the sun during the summer solstice so now I have to make that calculation based on about a 20 foot peak to see how the shadow line comes in to play. I will work on Jakes next. Amazing what is now at our fingertips. Winter was 31 degrees.

Thanks,
Joe

Comment by Jake Lappan on April 9, 2009 at 2:04pm: go to this website .

all you have to do is put in the area code of the building location and time zone to create a sun chart in PDF format that you can use to figure out the sun angles for the time of day during each month. You will then need to draw a wall section with your opening sizes and project your sun angles to figure out the desired length of your overhangs to block the sun in the summer time but let in as much as possible during the winter months. the image attached is an exaple of what i did for a project that wanted a passive soalr design. It allowed me to figure out the best overhang length. when it comes to a gable end it is harder to get the desired sun shading with out the rake overhang having to get out there pretty far but it can be done.