ABSTRACT

This paper studies the possibilities for improving daylight in mosques by measuring the illumination level under various domes in an old mosque "Mosque of Guzelce Hasan Bey in Hayrabolu" using an architectural physical model. The illumination level under the domes were tested under three different cases: a dome without openings (the original building), a dome with a central opening, and a dome with openings around the base. It was found that a dome with openings around the base brings an evenly distributed light all over the prayer hall during the critical hours of 12:00 p.m. and 3:00 p.m. In addition, it improves the quality and quantity of light.

1. INTRODUCTION

A mosque is a place in which Muslims come together for corporate prayer. The mosque is recognizable by its dome and its minaret. The minaret, which could be visible from a far distance and from all sides, is a landmark that indicates the locality of worship.

Domes are the architectural form that indicate the spanning of the inner spaces. However, a circular dome covers a lower structure that is square or hexagon. The prayer hall is perceived as a rectangular space when someone enters it; that rectangular space is covered by a dome or more than one dome (De miranda, 1977). When entering the hall, the worshipper faces the wall which is towards Mecca, Saudia Arabia. (The orientation of this wall depends on the location of the site.) That wall determines the direction of prayer.

The floor of the praying hall is always covered by carpets because Muslims perform their prayers on the floor and they perform reading, as well, while sitting on the floor.

Therefore, sufficient illumination level is required for the reading task.

Consideration of daylighting must be related to the time of day. Therefore, daylighting coming to the reading workplane level (six inches) should be evenly distributed during the day time prayers (12:00 p.m., and 3:00 p.m.). Sources of daylighting are the roof (skylights or dormer windows) and the walls (windows or full walls). Such lighting must be used with care so that glare does not reduce its usefulness by creating visual competition during the religious service (IES, 1993).

Due to the lack of prediction tools to anticipate daylight available from domes, most recent mosques ignore natural light, which causes excessive usage of artificial light and accordingly increases the energy consumption. There are qualitative issues, as well.

2. THE TESTED MOSQUE

Daylighting was examined in an old mosque. There are many mosques with prayer halls built more or less on a similar pattern as the mosque which was examined. Domes were used in most Ottoman Architecture buildings as part of their architectural style.

The mosque of Guzelce Hasan Bey in Hayrabolu, Tekirdag, was built in 1406 (Kuran, 1968). The oblong prayer hall is covered by five domes. The largest dome, high central dome on pendentives, spans the depth of the prayer hall from wall to wall. It is reinforced by a dodecagonal drum unperforated by windows. On the east and west of the central dome, there are two smaller domes separated by arches which spring from square piers (Figure 1).

The mosque has a fountain in its courtyard which is considered the earliest Ottoman mosque court still in existence. There is a minaret to the west of the mosque, located at the intersection of the prayer hall and the courtyard. The walls are heavy masses. The entire structure is built of horizontal courses of stone and brick.

3. DESCRIPTION OF METHOD

A physical model of a scale of 1=50 was used to simulate the daylight distribution inside the prayer hall and around the courtyard. The prayer hall has an area of 200 m². The central dome was constructed on the top of a square of 10 x 10 meters. Each smaller dome on the sides was constructed on the top of a square of 5 x 5 meters.

The physical model was built of thick foamcore panels to represent the thick walls. The panels were covered with black sheets from the back to avoid any light leak (Figure 2).

As tremendous amount of decoration and writings are on the interior surface of the dome, and on the walls of the prayer hall; therefore, the reflectance materials of the physical model for the domes, walls and floor were averaged to 30%.

A grid pattern was drawn on the ground floor of the model to mark at which point measurements were to be taken. The entire central dome of the prayer hall was removable to simulate three different domes with different openings, and to facilitate the process of placing the measuring devices.

The physical model was fixed to a base made of plywood with a small 6" x 6" piece of plywood attached to the bottom of the base. The small piece of plywood was attached to a tripod to facilitate orienting the model in all directions (Alturki, 1994) (Figure 3).

Licor LI-210-S illuminance meters, which are designed to measure the illumination in footcandles, were connected to a portable computer to read the illumination level from each licor using a computer program called "DATALIT", which was written at University of California, Los Angeles (UCLA), (Milne, 1986).

A sundial diagram (solar gnomon) was used for the same latitude as the original location of the mosque (40° N Latitude). The sundial gives the exact angle of the sun for a desired time of the day and a desired day of the year.

4. MEASURING THE RESULTS

The model was measured under clear sky conditions similar to the conditions of the original location of the mosque.

Several reference points were carefully chosen and distributed in different locations. several Licors were located in the prayer hall, and others were located in the spaces adjacent to the courtyard. They were located as follows:

4.1 The prayer hall:

1) The center of the central dome.

2) South of the central dome.

3) East of the central dome.

4) West of the prayer hall and between the smaller domes.

5) East of the prayer hall and at the center of the small dome.

6) South east corner of the prayer hall (Figure 1).

Readings were taken under three different cases for the central dome; a dome without openings, a dome with a central opening, and a dome with side openings (Figure 1).

4.2 The courtyard:

Several points were chosen, as shown on the plan of the mosque, and most of them were selected in spaces adjacent to the courtyard (Figure 1).

One light sensor was located totally outside the physical model to measure the total horizontal illumination.

The only prayer times during the day time are at noon and at 3:00 p.m. Therefore, the physical model was tested at these times on the 21 of each month using the solar gnomon and the tilting device mentioned above.

The prayer hall was photographed using a 28 mm camera, and ASA 400 daylight film to provide a permanent record of daylighting conditions inside the model (schiler, 1990).

5. ANALYSIS

The daylight factor was calculated from every measured point.

Daylight Factor (DF) = E_p / E_{exterior horizontal} (Schiler, 1992).

Preliminary data indicated that the primary variation of Daylight Factor (DF) for every reference point inside the prayer hall occurred due to the change in time and month.

All the output data was plotted in graphs showing the geometry of the prayer hall and in some cases part of the prayer hall; for instance, the central dome is simulated separately.

Fig. 3 The three different tested cases of the central dome. A) a dome without openings, B) a dome with a central opening, C) a dome with side openings. (opened for photo)

6. CONCLUSIONS

Several behaviors were observed from the measurements taken from the prayer hall and from the measurements taken from the spaces adjacent to the courtyard.

6.1. The Courtyard

It was found that the adjacent spaces receive good quality and a sufficient quantity of light all year long at the hours 12:00 and 3:00 p.m. Most of the light is basically reflected from the floor of the courtyard and from the opposite walls.

6.2. The prayer hall

There were different cases examined inside the prayer hall. The central dome was tested under three different openings. All the different cases were measured and compared to each other.

6.2.1 No Openings

The central dome with no openings (as the original mosque) provided the praying hall with very low illumination level. Most of the light was coming from the side windows on the north facing wall (Figures 4, 5 & 6).

6.2.2 Central Opening

The central dome with only one opening in the center provided better illumination than the first case. However, the north wall was still dark compared to other walls. In the mean time, the opening in the center brings more direct sunlight to the space which increases the solar gain and glare (Figures 4, 5 & 6).

6.2.3 Side Openings

The central dome, in the third case, has eight openings around its base. These are effectively side openings. In this case, the light received at the workplane level was evenly distributed over the area beneath the dome. Good quality and quantity of light was maintained, as well. Most of the light coming to the floor surface is reflected from the curved surface of the dome (Figures 4, 5 & 6).

6.3 At the other reference points in the prayer hall, measurements were taken a distance from the central dome. The output of the measurements showed improvement in the daylight quality and quantity as the side windows were used for the central dome.

Fig. 5 The Daylight Factor has increased by 40% at reference point # 5 when using side openings. The high DF on June 21 at 3:00 p.m. is caused by direct sun beams from the side windows which hit near the light sensor.

Fig. 6 The geometry of the space beneath the central dome showing the increase in the DF when using side windows.

7. RECOMMENDATIONS

Vertical fenestration at the base of the dome provides the best light (most evenly distributed, least glare, higher averages.)

The openings should start at the base of the curve of the dome. With deep walls and wide sills, most of the light is then reflected from the bottom of the windows towards the opposite curved surface of the dome. Subsequently, the light reflects to the workplane level in the prayer hall. This provides a good quality and quantity of light, since most of the light is diffused and reflected. This, also reduces the solar gain at the floor level.

Many architecturally rich interiors (particularly older

structures with darker marbles and mosaics) have been found to have low illumination (IES, 1993) . As was mentioned in this study, the reflectance of the walls and the interior surfaces of the mosque is 30 %, more light could be obtained if the reflectance were increased to 50 % or 70%. It is important to point out that the study intended to bring an evenly distributed light, and that was successfully maintained.
 

BIBLIOGRAPHY

(1) Alturki, Ibrahim, "Qualitative and Quantitative Natural Light in Atria and Adjacent Spaces", University of Southern California, Los Angeles, California, 1994

(2) De Miranda, F., "The Mosque, as Work of Art and as House of Prayer", Wassenaar, Denmark, 1977

(3) Illuminating Engineering Society, "Lighting Handbook, Reference & Application", 8TH ed. Illuminating Engineering Society of North America, New York, 1993

(4) Jeremy Robinson, "Religious Buildings", McGraw-Hill, 1979

(5) Kuran, Aptullah, "The mosque in Early Ottoman Architecture", University of Chicago Press, 1968

(6) Milne, Murray, "DATALIT Computer Software", University of California, Los Angeles, California, 1986

(7) Rivoira, G.T., "Moslem Architecture, its Origin and Development", Hacker Art Books Inc., 1975

(9) Schiler, Marc, "Simplified Design of Building Lighting", John Wiley & Sons, Inc., 1992

(10) Schiler, Marc, editor, " Simulating Daylighting With Architectural Models", DNNA, 1990
 
 

ASES 1996 – was filed ASES96b.doc,
is now ASES96mosques.doc