**5. Rawshan**

One of the most noticeable elements in historical Jeddah architecture is the *rawshan* which covers large areas of the building's facade. As mentioned earlier, it is a large wooden structure with a recognizable latticed component. Some buildings are characterized by vertical *rawshan* that extends to 3–4 storeys (**Figure 19**), while others contain horizontal ones. *Rawasheen* are normally found projected about 60 cm and are fixed with the aid of wooden cantilever.

*Rawshan* has many functional and aesthetical roles in the building. Beside protection from the harsh climate and solar radiation, it provides a resting place for two persons lying full-length with the ability to watch outside without being noticed. This is consistent with the privacy values. The lower and upper stripes of the

**Figure 19.** *View of historical* rawshan*, Noor Wali house.*

### *Sustainability Features of Jeddah Traditional Housing DOI: http://dx.doi.org/10.5772/intechopen.98735*

*Rawshan* are fixed wooden panels, while the middle contains shutters that can be lifted outwards and upwards to control the air to pass through creating gentle and continuous cross ventilation. The air passing through is employed to cool water contained in pottery grouped in identified place "*shurbah*". Around the top of the *rawshan* there is an ornate projected unit called a *rafraf*; Its projection promotes casting shade on the higher section. Another latticed component, known as the "*ghula*", is often hanging over the lower half of *rawshan* or windows to cover the interior spaces while the shutters are open providing additional privacy [19].

*Rawashan* provides natural gentle daylight with interesting patterns projected on internal walls and floors. Being finished with moderate soft colors that have a reasonable level of reflectance, *Rawshan* reduces glare in outdoor spaces caused by the building's white walls. Colors reflection determines the amount of light that will be directed inside. Its projection helps to shade the building's facade and the narrow surrounding paths.

*Rowshan* is also a flexible space that can be added to adjacent rooms. When necessary, it is flexible enough to perform the function of any type of rooms in the house. Too, activities taking place in a room can simply extend in *rawshan* as additional space (**Figure 20**). However, each *rawshan* is unique enough so that it is almost difficult to find two identical pieces in the whole area. There are endless varieties of sizes, shapes, treatments and organizations.

The indoor air temperature of two rooms with *rawshan* were examined from 5 to 31 August 2018. Rooms are typical, but one with opened *rawshan* and the other was closed. *Rawshan* could essentially regulate the indoor temperature during the high fluctuations. Median temperature in the rooms ranged between 32.3–38.4°C when the outdoor temperatures ranged between 30.9–48.7°C (**Figure 21**). Closed *rawshan* caused to delay heat transmission about three hours a day. But, when the *rawshan* was opened, the time regressed to one hour. The open *rawshan* allowed more airflow which mostly alleviated the rise of temperature. Similarly, night ventilation decreased the indoor air temperature assisted to decrease and postpone reaching peak time of temperatures in the space. Notably, these results are with the contribution of building's total thermal mass [20].

Results confirm that the relative humidity declines as air the temperature escalates and vice versa. Due to airflow into the room with opened *rawshan*, it lowered more heat acquisition and permitted relative humidity more than the room with

**Figure 20.** *Different functions of* rawshan *in the inside space.*

closed *rawshan*. Air velocity was measured at 0–8.1 m/s in the outdoor, 0 to 6.9 m/s in room with opened *rawshan*, and 0 to 1.1 m/s in room with closed *rawshan*. The highest frequency of air velocity values measured were found to be (2 m/s - 18.27%)

**Figure 21.** *A comparison between ndoor and outdoor air temperature during the investigated period.*

**Figure 22.** *Air movement through* rawshan*, opened (above) and closed (down).*

**Figure 23.**

*Daylight factor and daylight level of examined single glaze, closed venetians and* rawshan.

in the room with open *rawshan*, (0.5 m/s - 28.9%) in the outdoor and (0 m/s - 90.44%) in the room with closed *rawshsan*. Simulation by ANSYS R19.2 software proved comparable results (**Figure 22**).

The effects of *rawshan* on the performance of daylighting was examined with a computer model (Autodesk ECOTECT) to demonstrate its ability in reducing the glow of solar lighting in interior spaces. It was compared with closed venetians and single glazed windows of the same dimensions. *Rawshan* scenario proved efficiency on both daylight factor and daylight level (**Figure 23**) [21].

*Rawshan* is thus a passive mean that efficiently reduces buildings dependency on air-conditioning and artificial lighting and accordingly reduces energy consumption.
