Widya Kartika University, Dept. of Architecture

Jl. Dharmahusada Indah Barat VI/1

Surabaya, Indonesia 60285

Sun shading devices affect natural lighting, ventilation, solar gain, and overall building performance. Few architecture students, architects, and designers have applied solar shading as a useful tool to reduce glare, control light intensity and radiation, and minimize the cooling load on their project.

SHADING MASK is a computer-based teaching tool that uses Edward Mazria’s rectangular sun path diagram as a basis. The tool explains the basic theory of solar control, generates sun path diagrams; allows the design of overhangs, fins, and eggcrates types of shading devices; calculate solar angles and shading masks; and provides case study examples of actual buildings. It is a demonstration of how to integrate theory into a teaching / simulation tool to make important solar control information easily accessible to students, architects, and designers.

1. INTRODUCTION

Sun shading devices, either as parts of a building or separately placed from a building facade, affect natural lighting and ventilation, solar gain, and overall building performance. The role of sun shading devices or solar radiation control systems is taught at every school of architecture. Yet, only a few architecture students, architects, and designers have applied them to reduce glare, control light intensity, radiation, and minimize cooling load on their projects.

Using a well-designed computer program to teach, and re-

teach when necessary, the use of sun shading devices is

Marc Schiler

School of Architecture, University of Southern California

Watt Hall 204

Los Angeles, CA 90089-0291

more understandable, clear, and interesting than reading a book on the same topic. Having a readily available tool would also encourage architects and designers to use the shading devices as a method of conserving energy and lowering operating cost in the buildings that they design.

Visual Basic 3.0 was chosen as the development language for this Windows-based program. SHADING MASK uses Edward Mazria’s rectangular sun path diagrams as a basis. The program explains basic theory of solar control; generates sun path diagrams; allows the design of sun shading devices; calculates solar angles and shading masks; and provides case studies of actual buildings.

2. RECTANGULAR SUN PATH DIAGRAMS AND SHADING MASKS

The rectangular sun chart or cylindrical sun chart developed in Edward Mazria’s book (1979) titled Passive Solar Energy Book, provides multiple sun charts based on latitudes from 28 degrees north to 56 degrees north. The chart comes in form of vertical patterns (elevations) of sun’s movements. The bearing angle of the sun path is a horizontal sun angle measured along the horizon of the sun position, from west or east of true south. The solar altitude is a vertical angle measured between the horizon and the position of the sun at a certain time.

Any obstruction outside windows of a building, either trees, nearby buildings, walls, and shading devices can be added to the sun chart as shading masks. Mazria’s shading mask has three basic types: curved lines for overhangs, vertical lines for fins, and curved-vertical lines for eggcrates. All of them are drawn in elevations (Fig. 2.1).

a. Shading Mask for overhangs

b. Shading Mask for fins

c. Shading Mask for eggcrates

Fig. 2.1. Shading mask patterns based on Mazria’s book

3. THE COMPUTER PROGRAM

3.1. Sun Chart Diagram And Shading Mask

Since it is based on the rectangular sun chart method, the chart in this program comes in form of an elevation plane.

The most significant characteristic of the SHADING MASK program is its flexibility to plot a sun chart for any latitude, in one degree increments, for any time of the year. Users may display a specific daily sun path diagram (Fig. 3.1) or annual sun path diagram (Fig. 3.2). Various height to depth (h/d) ratios for overhangs and width to length (w/l) ratios for fins will produce different shading mask patterns. Users can manipulate these ratios and plot 100 %, 50 %, and 0 % shading masks easily. Fig. 3.3 shows one example of the shading mask overlaid on a daily sun chart. The time where a window is shaded can be read from this chart easily, either it is shaded completely, fifty percents, or unshaded completely. In this example, the window is shaded completely from sunrise to 10:00 a.m., and from 2:00 p.m. to sunset.

Fig. 3.1 Sun chart for 40 deg. North latitude on June 21.

Fig. 3.2 Sun chart for 40 deg. North latitude (annual).

3.2. Programming Structure

SHADING MASK consists of two executable program: Shading Mask and Theory. Both of them can be run independently. The user’s guide or the How To ... form gives help on how to use the program. The main screen (Fig. 3.4) has six pull-down menus: File, Shading Mask, Examples, Explain, Tables, and Help.

Fig. 3.3 Shading mask for south facing window with overhang overlaid on 40 deg. North latitude sun chart on June 21.

Fig. 3.4 The main screen and pull down menus.

The File menu has options to print and exit program. How ever, the "Print" menu can not for this version can not print a sun chart directly from the screen. Instead, users may print the chart and shading mask by pasting the graph to other Windows programs such as Write, Word for Windows, etc.

The Shading Mask menu is used to input ratios of window height to overhang depth and window width to fin length. There are instant, novice, and advanced options (Fig. 3.5). The "Advanced Options" offers more sophisticated options of overhangs and fins. Users have to type some values in the dialogue boxes provided on each form, then may see the result after clicking the "Shading Mask" button on the main screen.

Fig. 3.5 Advanced options dialogue box for specifying overhangs dimensions.

The Examples menu currently contains examples of ten existing buildings that use overhangs and/or fins. This menu enables users to study different types of shading devices applied on some existing buildings. Another option from this menu is that users may learn shading design by opening "Shading Example" menu.

The Explain menu is intended to provide users with a general theory of shading devices and help users develop a deeper understanding of solar control devices (Fig. 3.6). Besides, this menu also provides some clarifications about the main screen.

Fig. 3.6 Sample from theory section.’

The sun path diagrams can also be depicted as a table of numbers. This is done through the Table menu (Fig. 3.7).

Fig. 3.7 Table of 40 deg. North latitude sun chart on June 21.

The Help menu functions as a user’s guide. From this menu, a user can may learn how to use the program

independently (Fig. 3.8 and Fig. 3.9).

Fig 3.8 The Help menu.

4. EVALUATION OF THE PROGRAM

The intent of the program was to explain the basic theory of

solar control; generate sun path diagrams; allow the design

Fig. 3.9 A sample help page.

Fig. 4.1 The annual sun path diagram for 1 deg. North latitude (annual).

of overhang, fin, and eggcrate shading devices; calculate solar angles and shading masks; and provide case studies of actual buildings. Overall, the program reaches this goal and runs well. It is very simple and easy to understand. It is also very flexible in allowing many different variables to change. Yet, still some sun charts are confusing. This problem occurs when users choose latitudes below 24 degrees (north or south) and plot annual sun charts. In these latitudes part of sun path should be plotted on a different hemisphere (Fig. 4.1). Users are recommended to plot daily sun charts rather than annual sun charts for these latitudes to avoid this problem.

The print command in this program is basically a built-in

print instruction in Visual Basic 3.0. Undoubtedly, the resolution of a print out is dependent upon screen or monitor resolution. There are also many imperfect pictures in this program caused by low resolution from scanner images and other bitmap files.

The examples section of the program is also not as detailed as it should be, and an option should be added to provide Olgay style sun diagrams. And, of course, one could add additional options to the overhang and fin design including non-symmetrical arrangements and lightshelves.

5. CONCLUSIONS

Sun shading devices are important options for designers to consider to minimize heat gain, control daylighting, and protect walls from rain. We recognize that only cold climates areas do not need shading. Thus, sun shading devices are very important.

A better understanding of these devices will hopefully generate a desire to apply them on projects. SHADING MASK is a good demonstration of how to integrate theory into a teaching or simulation tool to make important solar control information easily accessible to students, architects, and designers.

Now filed as ASES96mask.doc

6. ACKNOWLEDGMENTS

I am grateful to G. Goetz Schierle, Douglas Noble, and Karen Kensek, of USC, School of Architecture. This program could not have been written without their supports and intellectual guidance.

7. REFERENCES

(1) Cornell, Gary, The Visual Basic 3.0 for Windows Handbook, McGraw-Hill, Berkeley, California, 1993

(2) Mazria, Edward, The Passive Solar Energy Book, Rodale Press, Emmaus, PA., 1979

(3) Olgyay, Aladar, Solar Control and Shading Devices, Princeton University Press, Princeton, 1957

(4) Setiadarma, Effendi, Shading Mask: A Computer-based Teaching Tool for Sun Shading Devices, A Master’s Thesis, Building Science Program, School of Architecture, University of Southern California, Los Angeles, 1995

ABSTRACT

Sun shading devices affect natural lighting, ventilation, solar gain, and overall building performance. Few architecture students, architects, and designers have applied solar shading as a useful tool to reduce glare, control light intensity and radiation, and minimize the cooling load on their project.

SHADING MASK is a computer-based teaching tool that uses Edward Mazria's rectangular sun path diagram as a basis. The tool explains the basic theory of solar control, generates sun path diagrams; allows the design of overhangs, fins, and eggcrates types of shading devices; calculate solar angles and shading masks; and provides case study examples of actual buildings. It is a demonstration of how to integrate theory into a teaching / simulation tool to make important solar control information easily accessible to students, architects, and designers.