Sun Shade Calculator for Lahore, by Sarah Khan

1. Sun Shade Calculator for Lahore Sarah Khan

2. Energy Efficiency and Sustainability Introduction Energy efficiency is an integral part of architecture. One of the simplest and most basic passive techniques, that is universally applied for hot climates such as that of Pakistan, is that of solar shading.

3. Energy Efficiency and Sustainability Introduction This presentation gives an overview of the existing methods of providing shade from the Sun. Additionally, a new technique is proposed and the verification of the reliability of this new method is also undertaken. Finally, there is an explanation of the diversity and limitations of its application, its scope and future prospects.

6. External Vs. Internal Shades Introduction Both external and internal shades control heat gain. External shades are more effective than internal shades because they block the solar energy before it enters the window. (In fact, stopping the sun’s heat before it penetrates windows and openings is up to seven times more effective than using interior blinds or curtains. 1 ) When using an internal shade, such as blinds or a curtain, the short-wave radiation (light) passes through the glass and hits the shade. Depending on the colour of the shade, some percentage will be reflected straight back out the window, but the rest will be absorbed by the shade itself, effectively heating it up. Some part of the incoming short-wave radiation will also already have converted into long-wave radiation (heat waves). Thus, even though internal and external shades seem to be doing the same job, their effect on the performance of the building is quite different. 1 A quote by U.S. Department of Housing and Urban Development, taken from the article ’Shade screens and window treatments’, by Arizona public service APS company,1999.Retrieved from www.apsc.com; May,2005.

7. The Problem Introduction The efficient design of a window shade - that which allows the Sun to penetrate in winter but not in summer - is a basic requirement that every architect aspires to achieve.

10. The Proposed Solution Introduction The proposed solution is a software /calculator that is different from the available software, in that it is a Specific software, as opposed to all the existing General software. While a generalized software can respond to any global location; it can be quite time-consuming and complicated and therefore would always require extensive pre-calculations. A specific software on the other hand may not have global appeal but it can significantly ease the situation for a specified target audience. It becomes simpler for the user as it is possible to programme into it almost all the pre-calculations that would otherwise be required of the user.

18. Calculations Software Development The equations for other shade types were derived from these basic ones, and programmed into the calculator. For example, for angled walls and angled horizontal louvers, the equations are: Length ‘l’ = (h/n) sin ( b- VSA) sin (180 – a – b + VSA) width = depth x sin a sin (180 – b ) where H=height of opening a = angle of inclination of shade, b = angle of inclination of wall Additional checks were introduced in the software to give a value of zero for the orientations when a shade is not required. a b

20. The Layout The Software shadecalculator.xls

22. The Graphical Method Results Analysis 1: Verification The shade parameters, as calculated by the Shade Calculator are:

24. Analysis 1: Verification The Graphical Method Results

25. Self-Verification Analysis 1: Verification The shade parameters, as calculated by the Shade Calculator through different sheets are identical, even though completely different formulae are used; The simple Horizontal shade calculator uses formulae available in literature. E.g. D=H/tanVSA The Horizontal shade calculator for angled walls and angled shade uses formulae derived through this research. E.g. D=Hxsin(b-VSA)/sin(180 o - a-b+VSA)

26. Computer Simulation Analysis 1: Verification The computer simulation results for the test window, showing Solar Shading patterns for the Summer equinox (21 st June; 12pm), as well as the Autumn equinox ( 21 st September; 4pm.) Ecotect

27. Application Analysis From the Specific to the General The designed software is for Lahore, i.e. 31.5 o N and 74.18 o E. The software is applicable to any area around the globe that falls into the 31.5 o N latitude band. The above analysis shows its applicability between 30.5 o N – 32.5 o N with considerable accuracy. For Pakistan, its applicability can extend to such cities as: Sheikhupura=31.42 o N Faislabad=31.25 o N Gujranwala=32.09 o N Dera Ismail Khan=31.65 o N 5.5% 60.65 50.4 230.7 48.6 30.0 o N 4.2% 60.35 50.3 230.3 48.3 30.5 o N 2.1% 59.80 49.9 229.9 47.9 31.0 o N 0% 59.28 49.4 229.4 47.6 31.5 o N 1.68% 58.81 49.0 229.0 47.3 32.0 o N 3.78% 58.33 48.6 228.6 47.0 32.5 o N 5.88% 57.78 48.2 228.2 46.6 33.0 o N % Error VSA (For South) HSA (For South) Azimuth Angle Altitude angle Latitude

28. Use

29. Examples of Shades & How to design them Use How to Calculate shade: Treat it as a Simple Horizontal shade on a curved wall. The McLaren Technology Centre Architect: Norman Foster. Location: Approx. three km north of Woking town centre, Surrey, UK. Diwan-e Khas, Lahore Fort

30. Examples of Shades & How to design them Use Autodesk trademark image for sustainable design using Autodesk software Publishers united limited; Anarkali. How to Calculate Shade: Simple Horizontal + drop down shade.

31. Examples of Shades & How to design them Use How to Calculate shade: (For the school) Vertical Louvres; Horizontal + Louvres + Simple Vertical Shade.) Greenwich Millennium Village primary school. (Edward Cullinan Architects.) IKEA

33. The Shade Calculator’s Future Conclusion The focus of this research was to produce a simple equation calculator that requires input of window parameters and orientation, etc. and gives results in terms of shade parameters. Comparison with existing softwares…just as accurate?

34. The Shade Calculator’s Future Conclusion The use of a familiar environment (Microsoft Excel) should hopefully ensure that it remains user-friendly and easy to operate. Making it city-specific ensured that most of the climatic data, and other related tedious calculations have already been fed into it; making the input requirements minimum. The end result is hopefully simple, easy to comprehend and simple to operate. The present computer-friendly generation of architects should find this an extremely easy and quick method of shade calculation, and this calculator should hopefully prove very useful and may promote a more pro-sustainable attitude from the designers.