**4. Results of the Case Study Analysis**

The tables below contain a summary of the cases investigated in this study. Windcatchers started showing up during the Pharaonic and Coptic eras, but the shape, the number of sides, orientation, and openings seem to have been developed further during the Islamic era, when there was more understanding of wind movement and direction prevalence (see Figure 6) [12,17]. Table 2 shows that 85% of the windcatchers in Egypt are either single-sided or two-sided, and most are oriented toward northern and western directions. This study consisted of 12 case studies from the Pharaonic to the Coptic to the Islamic eras. Overall, 50% of the cases of windcatchers studied from the aforementioned eras are single-sided. Moreover, 33.3% of them are two-sided, all of which have their openings adjacent to each other, and all of which are from the Islamic era. In total, 75% of the two-sided windcatchers face north and west, which is the span of the prevalent wind directions in Egypt (see wind rose in Figure 39a). Furthermore, there are cases for which the type and orientation of the wind towers are unknown since they no longer exist [10].

(**e**) Abu Dhabi, UAE (**f**) Doha, Qatar

**Figure 39.** Wind roses in the regions studied. (Note: wind roses are available at the website: World-Weather Weather Archive in Yazd Available online: https://world-weather.info/archive/ accessed on 16 April 2023/).

The table further explains how windcatchers changed from the Medieval to the Modern era. Overall, 37.5% of the modern case studies have windcatchers that follow the design standards of vernacular windcatchers. Nonetheless, it seems that Hassan Fathy developed the *malqaf*, as seen in the cases of the Luxor Cultural Center and Experimental

Rooms for the Ministry of Scientific Research, where the openings of the windcatchers face opposite directions. A study examining various windcatcher design parameters as a means for the passive cooling of low-rise buildings in Egypt during the summer shows that an iteration similar to Hassan Fathy's resulted in the highest air change per hour [48]. For example, none of the ancient or medieval windcatchers are flat-roof, and 37.5% of the modern windcatcher case studies have flat roofs. The effectiveness of modern flat roof windcatchers is yet to be studied in Egypt's climatic conditions.

Table 3, on the other hand, indicates that wind towers throughout the Middle East varied in type, ranging from single-sided to cylindrical types. It is worth noting that both modern wind towers studied are cylindrical. The shapes found in the tables below align with the findings in Table 1 [9].

The following wind roses in the various studied regions determine if the windcatchers studied here considered the prevalence of the wind. Cairo's wind rose shows that the prevailing wind comes primarily from the north and northwest. More than 32% of the wind appears from the north, followed by more than 27% from the northwest. No wind whatsoever comes from the span between the south and east, and negligible amounts of wind are received from the remaining directions (Figure 39a). This explains why wind towers in Cairo are typically single-sided or two-sided. It would be useless, and maybe even harmful to the speed of the wind coming in, to have many unnecessary openings in the tower's design when only one general direction is receiving most of the wind.

Like Cairo, Yazd's wind rose shows that most of the wind comes from the northwest and north. More than 29% of Yazd's wind appears to come from the northwest. This is followed by slightly more than 21% from the north. On all other sides, very little wind is received (between 4 and 11 percent) (Figure 39b). This explains why wind tower designs in Iran vary in their number of sides, as all sides receive wind, even if very little, as seen in the examples above for the tower of Dolatabad and the Ganjali-Khan Square windcatchers. Therefore, the designs depend on each area's specific prevailing wind directions.

In Dubai, the wind rose indicates that the wind comes primarily from the northwest and west. Slightly more than 40% of the wind in Dubai comes from the northwest. This is followed by more than 30% coming from the west. Almost no wind at all comes from the span between the southwest and northeast (only between 0.9 and 2.1 percent) (Figure 39c). Even though there seems to be a prevalent wind direction (northwest) in Dubai, the windcatchers found in Bastaqyia, Dubai, UAE are four-sided, which might seem contradictory to the typical use of one-sided windcatchers for places that have a prevalent wind direction.

The prevailing wind in Iraq is generally from the northwest, comprising 33.4%, followed by the west and the north follow, with each receiving approximately 18% of the wind. Based on the information on the wind rose shown in Figure 39d, single-sided windcatchers, just like in Egypt, are understandably used in Iraq, as the above example of Diwan-Khanat al-Asterabadi shows. However, the direction of the particular windcatcher that faces northeast does not align with the wind rose.

It is evident from Abu Dhabi's wind rose that the prevailing wind direction is northwest. It receives notable 51.1% of all the wind in Abu Dhabi. This is followed by less than half that amount received in the north (only 22.6%). All the other sides receive very trivial amounts of wind (between 1.8 and 10 percent) (Figure 39e). This can explain why the wind tower designs in this region vary, along with the previous wind rose from the Emirates. There is a high level of variance in the wind statistics from one region to the next; therefore, the design also varies in response to the wind statistics.

Lastly, Doha's wind rose indicates several diverse prevailing wind directions. This is because the differences between them are minimal. Doha receives 26.9% of its wind from the north, 26.7% from the east, and 22% from the northeast. The northwest direction receives slightly less, at almost 14%, and the southeast direction is slightly lower, at almost 9%. The rest of the sides receive negligible amounts of wind (<1%) (Figure 39f). This explains why there is diversity in the wind towers, which typically have many sides.



**Table 3.** Types of windcatchers throughout different eras in Middle East.


#### **5. Discussion and Conclusions**

Although building height differences and homogeneity in the urban area are important factors for urban ventilation performance in an area [49], as studied in old cities such as Elazı ˘g, this study did not address this point since urban morphology surrounding the case studies has changed throughout history. Therefore, this study relied on a wind rose analysis for each region.

In conclusion, the wind roses in the regions studied in this paper explain why the wind towers were designed the way they were. Some regions, such as Cairo, Dubai, Baghdad, and Abu Dhabi, receive wind in mostly one primary direction. Therefore, a one-sided or two-sided windcatcher is the prevalent choice in Cairo. Using two-sided windcatchers that are open on both the north and the west sides is especially beneficial because it supplies the building with the wind in the direction that ranges from north to northwest to west, which are the three most prevalent wind directions in Cairo. These results highlight that the vernacular windcatchers in Egypt and the Middle East correspond to the prevailing wind directions and the ventilation needs of the connected spaces. However, in Dubai, the use of four-sided windcatchers contradicts Dubai's wind rose, which shows a limited range in wind direction (even more limited than that of Cairo's). This could be because the Dubai windcatchers were built by Persian immigrants who were probably used to constructing four-sided windcatchers in Iran. Other types with more sides are better in regions with variable wind directions, such as Yazd, Iran [50].

Another aspect guiding the windcatcher design is its relationship to other spaces.

In Egypt, most of the windcatchers open directly into an enclosed space, whereas in other regions of the Middle East, windcatchers are used differently, where most of them are attached to open spaces or courtyards. This may also explain why windcatchers in Egypt are mostly unidirectional since they ventilate one specific space. In other regions, even if there is one direction for prevailing wind, we found multi-directional windcatchers, which ventilate a larger attached open space.

In Egypt, many modern windcatchers followed the design standards of medieval windcatchers. This can be evidence of the success of this design, albeit simple. On the other hand, Hassan Fathy tried to develop the vernacular windcatcher to have its openings face opposite directions. A study shows that an iteration similar to that resulted in the highest air change per hour [50]. Furthermore, the tables above show that 37.5% of the case studies on modern windcatchers have flat roofs. Further studies should be performed to measure the effectiveness of modern flat roof windcatchers in the climate of Egypt.

In the gulf, where the wind is scarce and the climate is harsh, new technologies are added to the wind tower to cool outdoor spaces rather than indoor spaces, such as in the cases of Masdar City in the UAE and Khalifa Stadium in Qatar.

A limitation of this study is that most of the windcatchers from the Pharaonic to the Medieval eras did not survive in Egypt since they were mainly made of wood or reed [12]. However, the cases of both the Madrasa of al-Na¯s.ir Muh. ammad and The Khanqah of Sultan Baybars al-Jashankir, which do not have surviving windcatchers [12,19,24,26] prove their prevalent use during the Medieval era. There is evidence of the use of windcatchers in cases such as those in the presence of wind ducts. An extension for this research may include using extensive field and numerical studies, which could provide more insight into the design of historical windcatchers, thus advancing the research on sustainable vernacular elements such as the windcatcher. Additionally, combining a windcatcher analysis with current research on the effect of urban configurations on airflow and ventilation [49] could help provide new information on how to utilize these elements to improve ventilation in existing and new neighborhoods.

**Author Contributions:** Conceptualization, M.A.N., A.E. and V.B.; methodology, M.A.N., A.E. and V.B.; formal analysis, A.E and M.A.N.; investigation, A.E. and M.A.N.; resources, A.E., V.B., M.A.N. and N.S.; data curation, A.E., V.B. and N.S.; writing—original draft preparation, A.E., N.S., M.A.N. and V.B.; writing—review and editing, V.B., A.E., M.A.N., S.G. and K.T.; visualization, M.A.N. and A.E.; supervision, S.G. and M.A.N.; project administration, A.E., M.A.N. and S.G.; funding acquisition, S.G and K.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded through an internal grant from the American University in Cairo offered through the Office of the Dean of the School of Sciences and Engineering (2021–2022). Supplementary funding from the Office of the Associate Provost for Research, Innovation, and Creativity funded the APC.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** The authors would like to thank the Office of the Dean of the School of Sciences and Engineering at the American University in Cairo for the funding offered to this project and the Office of the Associate Provost for Research, Innovation, and Creativity for the additional publication support funds revived. The authors would also like to thank the Rare Books and Special Collections Library at the American University of Cairo for giving us access to materials in their collections that have helped illustrate this manuscript. The authors would like to thank and acknowledge the excellent English editing of Laila El Refai. The authors would like to thank and acknowledge the technical support offered by the collaborating members: Omar AbdelAziz, Khaled Nassar, Moataz ElDakroury, and Ahmed Hafez.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

#### **Glossary**

