101
5
Airflow in Places of Worship
The selection and control of the cooling, ventilation, and air conditioning sys-
tems to provide controlled internal conditions in historic and heavy-weighted
buildings require knowledge not only of the effectiveness of the proposed
system providing the required conditions quickly and efciently, but also
of the long-term effects of the system and any sudden uctuations of the
internal climatic conditions on the comfort and life of the building envelope
itself and any works of art therein. Places of worship are of high spiritual
nature and commonly architecturally elite. The occupants are usually pray-
ing either standing or standing, bowing, and kneeling. The level of activities
should be accounted for in the thermal load calculations. Two examples are
shown here: the Grand Mosque extension project in Mecca, Saudi Arabia,
and St. Mary’s Orthodox Church in Cairo, Egypt.
In the mosque, ve obligatory prayers are performed daily; the average
period of time for any prayer lasts from around 15 to 20 min. When perform-
ing a congregational prayer in mosques, Muslims are guided by a leader
called imam. The imam stands at the front wall of the mosque facing mihrab,
which is a semicircular niche in the wall of a mosque and indicates the qibla,
that is, the direction of the Kaba in Mecca, and hence the direction that all
Muslims should face when praying.
During prayer, the imam performs movements including postures such as
standing, bowing, and sitting. Verses or chapters from the holy Qur’an are
recited while standing. Therefore, for all intents and purposes the activities
of all the participant prayers are synchronized behind the imam, and may be
considered to be the same.
Therefore, within accepted Muslim practice, any intentional action result-
ing from unaccepted indoor thermal conditions or any movement departing
from the actual performance of the prayer is not allowed and would make a
person’s prayer invalid. However, in Egypt and most other Islamic countries,
participation in congregational prayer in mosques is very common. With
some exceptions, all the mosques are normally occupied by males only,
because females are highly encouraged to pray in their home, especially the
ve obligatory prayers.
102 Air Distribution in Buildings
5.1 People and Comfort
5.1.1 Comfort Criteria
Thermal comfort is maintained when the body is in thermal equilibrium with
its surroundings. The human body exchanges heat with the environment
through convection, radiation, evaporation, and conduction to solid objects.
5.1.2 Effect of Air Movement
Air ow patterns have very important roles in transferring heat, species, and
particulates into the space and have to be comprehensively investigated.
5.1.3 Acceptable Comfort Zone
The acceptable comfort zone shall be as prescribed by ASHRAE Standard
55.
2
The acceptable ranges of operative temperature and humidity for per-
sons in a typical summer are 0.35 to 0.6 Clo and in winter 0.8 to 1.2 Clo
at near sedentary (<1.2 met) activity levels. Considering comfort zone, air
movement, and moisture content, in the present examples predictions
were obtained by simulating a worshiper’s body as a vertical rectangular
box1.75m height × 0.25 m width × 0.5 m length, as shown in Figure5.1.
5.2 Climatic Factors
5.2.1 Climatic Elements Affecting Natural Cooling
The local climate affects the building’s energy efciency, the comfort of its
occupants, and its resistance to weathering.
FIGURE 5.1
Worshiper modeling.

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