RE: to design overhangs

[Michaël Kummert <kummert@xxxxxxxxxxxxx>]

Dear Helmi Ben Rejeb,

You can find some rules of thumb on the web:

www.eren.doe.gov/consumerinfo/refbriefs/cb1.html
- Cold climates: Locate shadow line 
  at mid-window using the June 21 
  (summer solstice) sun angle.
- Moderate climates: Locate shadow 
  line at window sill using the June 21 
  (summer solstice) sun angle.
- Hot climates: Locate shadow line at 
  window sill using the March 21 
 (vernal equinox) sun angle.

www.ncsc.ncsu.edu/fact/22body.htm#overhangs has other design rules.

I did not find anything about wing walls.

Please note, however, that running many TRNSYS simulations with different
designs is not a bad idea, because it will allow you to estimate the effect
of overhangs and wing walls on your particular building with your particular
weather data. The dynamics of the building may have a large influence on the
impact of shading devices. Rules of thumb like the ones here above should
help you to choose a good starting point and to reduce the number of runs.

Chapter 14.4 of "Solar Engineering of Thermal Processes" (Duffie and
Beckman) also discusses overhangs. An interesting remark is that the effect
of overhangs is often overestimated because designers tend to  forget that
the sky diffuse radiation and the ground reflected radiation are practically
not shaded by such devices.

If you need more scientific information, I would recommend you the following
reference: 
Utzinger & Klein - "A method of estimating Monthly Average Solar Radiation
on shaded receivers" - Solar Energy, 23, 369 (1979).

I hope this helps,

Michaël Kummert

_________________________________________________________

Michaël Kummert

Solar Energy Laboratory - University of Wisconsin-Madison
1303 Engr Res Bldg, 1500 Engineering Drive
Madison, WI 53706

Tel: +1 (608) 263-1589
Fax: +1 (608) 262-8464
E-mail: kummert@engr.wisc.edu (*****NEW*****)

SEL Web Site: http://sel.me.wisc.edu 
TRNSYS Web Site: http://sel.me.wisc.edu/trnsys


-----Original Message-----
From: owner-trnsys@relay.doit.wisc.edu
[mailto:owner-trnsys@relay.doit.wisc.edu] On Behalf Of helmi ben rejeb
Sent: Tuesday, January 28, 2003 06:58
To: trnsys@relay.doit.wisc.edu
Subject: Re: to design overhangs


Dear M. Serres
Actually, the type 34  allows us to simulate overhangs and wingwals, 
only we have the exact dimensions of the overhangs. But what I'm 
looking for, is what the dimensions should I take to make the best 
profit from my overhangs. Of course I can make a multitude of 
simulations and let the dimensions as parameters which I change, 
until 
have the the best results. I'm working on a large project, and 
overhangs is a little part of it. I think that architects have a 
simplified method to design overhangs knowing the dimensions of 
windows. Can You help me?
Best regards








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