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Determining Heat Losses and Heat Gains Through The Building
Envelope of The Mosques
Ahmet Bircan Atmaca1, Gülay Zorer Gedik2
1Yıldız Technical University, Department of Architecture, 34353, Istanbul, Turkey
2Yıldız Technical University, Department of Architecture, 34353, Istanbul, Turkey
ABSTRACT. Mosques are religious structures used at different times of the day and vary in
intensity depending on the days. For this reason, when compared to a typical residential or office-
type building, it needs to be evaluated differently in terms of energy consumption and building
envelope. In this context, it is aimed to determine the effect of heat energy losses on the building
envelope of the two mosques having different heating, cooling and ventilation systems and
different building envelope properties. The sampling mosques are located in the province of
Istanbul with a temperate humid climate type. The mosques were built in 2012 with modern
materials and construction techniques. While Hz. Ali Mosque is being built with classical style
Ottoman Mosque architecture, Marmara Theology Mosque is designed inspired by the swallow
ceiling technique which is characteristic of Seljuk architecture. Heating, cooling and ventilation
are done by air conditioning system in Marmara Theology Mosque's. In Hz. Ali Mosque,
windows provide natural ventilation and the interior is heated with floor heating system and split
air conditioner. The facade design of mosques is different. To determine the heat loss and gain
from the building shell, the temperature of building envelope was observed with the Fluke Ti27
thermal imager. When the images were taken, Indoor temperature and thermal comfort were
measured with TESTO 480 Anemometer Thermal Comfort Measuring Device in The Mosques.
The findings are evaluated and the effect of heat energy loss-gain on the building envelope is
investigated and suggestions are presented.
1 Introduction
The industrial revolution in 18th century and
developments in the industrialization as well as
the increase in living standards around the
world, increase the need for energy resources.
According to the research, primary energy
consumption between 2010-2040 around the
world will approximately increase 56% [1,2].
The decrease in energy resources and increase in
the population in 21th century, conservation and
sustainability of the energy has become
mandatory. Major part of the energy
consumption is allocated to maintain comfort in
housing or public areas. Effective energy usage
and preservation in the buildings depends on
effective energy design.
In this study, the effect of building envelope on
indoor temperature and thermal comfort is
investigated for two mosques with different
heating, cooling, and ventilations systems in
December 2016 in İstanbul which is located in
the temperate humid climate region of Turkey.
To determine the thermal losses and gains in the
building envelope, Fluke Ti 27 Thermal
Cameras are used to take image samples from
the building façade. To determine the indoor
temperature and thermal comfort, measurements
are made with Testo 480 Anemometer Thermal
Conform Measurement Device.
2 Thermal Comfort in Buildings According to
Fanger Method (PMV-PPD)
P.O. Fanger has developed a model with 1300
people to determine the constant ambient
conditions in climatized buildings in temperate
humid climate regions when he was in college in
1960. Fanger combines psychological
perception and statistical data and created a
scale that predicts thermal precision of
271
individuals [7]. Fanger generated PMV
(Predicted Mean Vote) scale that covers the
individual satisfaction states according to indoor
temperature, air velocity, mean radiation
temperature, relative humidity, individual
activity level, and clothing insulation values.
Since developed PMV-PPD scale is applied with
participation of limited individuals in certain
indoor conditions, seven thermal sense were
created for ASHRAE standards and the scale
enables to be used in different climate regions,
and various building types. ASHRAE-7 thermal
sense scale is used to determine the individual
sensitivity of the people who are in the
environment [8].
PPD (Predictive Percentage Dissatisfaction)
value is the percentage value that states the
thermal dissatisfaction of the people in the
environment by using the PMV value. Comfort
range should be identified on PMV-PPD scale to
determine the thermal comfort in different
building and climate types. The comfort zone
for the PMV-PPD scale is -0,5<PMV<+0,5 and
PPD <10% according to numerical calculation
for the environment [5]. To have healthier
results from PMV-PPD scale created in the
laboratory environment in real life application,
the thermal sense range perceived by the users
of the environment should have a comfort zone
of slightly cool (-1) and slightly warm (+1) in
the ASHRAE-7 thermal sense scale [5].
The study has evaluated measurement results
according to PMV-PPD thermal comfort scale to
determine the appropriate thermal comfort
conditions. PMV-PPD is divided into 3
categories in terms of sensitivity. Category A is
-0,2<PMV<+0,2 and PPD<6%, category B is -
0,5<PMV<+0,5 and PPD<10%, category C is -
0,7<PMV<+0,7, and PPD<15%. As the number
of individuals and age range in the mosque are
variable, the measurement results are evaluated
for category B. Comfort zone is accepted as -
0,5<PMV<+0,5 and PPD<10% as determined
by ASHRAE-55 and ISO 7730 standards [5,6].
3 Energy Conservation and Building
Envelope Effect in Mosques
As the technological developments are
enhancing day by day, HVAC systems for the
buildings are developed. To create a uniform
thermal comfort in the buildings, thermal
performance of structure envelop is important
for conservation of energy. In addition to quality
of heating, cooling, and ventilation systems in
the buildings, heat transfer resistance of
materials used in building envelope are also
effecting the amount of energy consumption.
Mosques are important public areas in the
Islamic countries. The one third of the
consumed energy in Turkey is caused by the
non-domestic public buildings [3]. Mosques are
prayer structures for Muslims that are used in
different periods of day, that has different usage
density. TÜİK 2013 data shows that there are
85,412.00 mosques in Turkey with various size
[4]. Since the mosques provide services to wide
range of users in different time periods, thermal
comfort and thermal energy conservation can be
challenging. Religious buildings have an
important place in many countries. Although
mosques have similar architectural properties in
Islamic countries as well as other countries,
design and material can be different.
3.1 The Relationship Between Thermal
Energy and Thermal Comfort in Building
Envelope of the Sample Mosques
Sample mosques are in İstanbul municipality
which is in the temperate humid climate region
of Turkey. The thermal camera images from
Marmara Theology Mosque and Ali Mosque in
Figure 1 demonstrates the thermal comfort
measurements which were made in winter, on
December, at 12.30-13.30. The air temperature
is 4-6 oC, relative humidity is 50-75%, and outer
air speed is 1.5-4m/s on the measurement days.
272
Figure 1.Marmara Theology Mosque and Ali Mosque
Marmara Theology Mosque is defined as a
single domed mosque with the combination of
modern design and Ottoman architecture.
Heating, cooling, and ventilation systems are
resolved with mechanical systems. Although the
building envelope has glass surfaces, the
window system is not suitable for natural
ventilation. As seen on Figure 2, two entrance
doors of Marmara Theology Mosque are
directed to north and west. The mosque is
situated on southeast-northwest axis. There are
no high-rise buildings to prevent direct sunlight.
The heating system inside the mosque is
provided with PVC cables inside the carbon film
under the carpet which is operated by electric
energy and by mechanical cooling system forced
by pipelines located on the upper edges of the
glass surfaces inside the building envelope. The
grid located on the front section of the glass
surfaces are absorbing the indoor polluted air.
Ali Mosque is built according to Ottoman
mosque style in 2013. The mosque is heated by
split air-conditioners on the walls and PVC
cables inside the carbon film under the carpet.
As shown on Figure 2 the ground floor plan of
Ali Mosque consists of two section. There are
two sections; entrance and main section. The
entrance in the building is functioning to
provide a prayer area for the last individuals and
as a wind shield. The windows on the building
envelope are helping the natural ventilation. The
blue coloured areas on Fig. 2 are glass surfaces.
Figure 2 Ground Floor Plan of Marmara Theology Mosque and Ali Mosque
273
The roof of Marmara Theology Mosque is
formed by covering the steel construction with
wood and fibro-concrete. In the building
envelop sections shown in Figure 3, the steel
carriers are bundled with rock wool of 4 cm
thickness. The details of the roof are galvanized
sheets and polyurethane spray waterproofing on
glass. On the glass surfaces, there are 4 pieces of
glass plate with 6 mm depth. There is a 20 mm
gap between the dual glass surfaces. There are
ornaments made of fibro-concrete to function as
a sun reflector on the surface of the glass facing
the outer centre.
Figure 3 Dome and Glass Surface Cross-Sectional Details of Marmara Theology Mosque
3.2 Heat Loss-Gain and Thermal Comfort
Analyses on Building Envelope of Marmara
Theology Mosque
The thermal images obtained to determine the
heat losses and gains on the building envelope
of Marmara Theology Mosque, it is evident that
large glass surfaces are causing heat losses. The
temperature value of the air conditioning system
that blows hot air from the glass surfaces is
shown on Fig. 4. It has been found that the
temperature values decrease as approached from
the heaters to the central areas of the glass
surfaces. Thermal camera images taken under
closed sky conditions show that there are not
significant temperature differences depending
on the directions.
274
East Side
PMV -0,34, PPD % 7,42
PMV +0,01, PPD %5,34
West Side
PMV +0,08, PPD %5,26
PMV +0,03 PPD %5,18
SouthEast Side and
NorthWest Side
PMV +0,06, PPD %5,25
PMV -0,26 PPD %6,4
Figure 4 Thermal Camera Images and Thermal Comfort Measurement Values of Marmara Theology
Mosque
According to ISO 7730 and ASHRAE 55-2013
standards, PMV-PPD measurement values,
which are made according to directions in the
Marmara Theological Mosque, are among the
thermal comfort values [5,6]. It is found in the
thermal camera images that the U-value is very
low on the surface of the building, whereas the
glass areas are the weakest regions on the
building envelope despite the use of heat-
strengthened glass. Different temperature values
are determined in glass surfaces which are in the
different parts of the building envelope. The fact
that the temperatures at the entrance of the
mosque are higher than the glass surfaces
indicates that the double entry system has been
successfully applied in the doors, and that the
wind protection is important. The Marmara
Theology Mosque, where the climate system
and the floor heating system are applied, is
comfortable in terms of thermal comfort values.
3.3 Heat Loss-Gain and Thermal Comfort
Analyses on Building Envelope of Ali Mosque
In Ali Mosque, thermal camera images obtained
under closed sky conditions and measured
thermal comfort values are found to be
uncomfortable in terms of thermal comfort in
winter season conditions of indoor environment.
In the mosque, open flooring type split air
conditioners are positioned in front of the walls
for heating purposes. There are no heating
devices in front of the window that has the
maximum amount of heat loss.
275
East Side
PMV -1,63, PPD % 57,72
PMV -1,52, PPD %45,34
West Side
PMV -1,77, PPD %65,2
PMV -1,63 PPD %58,11
SouthEast Side and
NorthWest Side
PMV -1,75, PPD %64,43
PMV -1,79 PPD %66,16
Figure 5 Thermal Camera Images and Thermal Comfort Measurement Values of Ali Mosque
21 ° C (28.45 ° C -7.49 ° C) temperature
differences are detected between the surface of
the glass and the glass front in the images where
the glass surfaces are detected as the coldest
area.(Figure 5) It is observed that although the
heating system and the split air conditioner are
operated together, the ambient temperature is
outside the comfort range in terms of thermal
comfort values according to ISO 7730 and
ASHRAE 55-2013 standards. It has been
determined that the temperature values are low
in the southeast region of the mosque, although
there is no window or any openness that may
cause any heat loss. The reason for this is that
only the floor heating system is considered as
the heater in that area and the indoor heaters are
insufficient.
4 Results
The study is presented to investigate the heat
loss-gains of building envelop properties and the
effects of current air conditioning systems on
thermal comfort in mosques. The heat loss based
on glass type and materials on the building
envelope in the mosques are analysed. The
thermal comfort values of the sample Marmara
Theology Mosque are between ISO 7730 and
276
ASHRAE 55-2013 standards values although
the glass surfaces cover a larger area. Although
building surface of Ali Mosque is covered by
lower glass surface amounts, the mosque is
outside the comfort region of the standards.
The outcomes for energy conservation according
to thermal camera images and thermal comfort
measurements on current samples are indicated
below.
• Regardless of the fact that glass surfaces
cover a large area on the building envelope of
the mosque design, when appropriate thermal
transmission coefficients are provided, the heat
loss values are minimized.
• If appropriate thermal transmission
coefficient isn’t achieved event though the glass
surfaces on the building envelope cover a
smaller area, these areas are determined as weak
areas where heat losses occur. The glass
surfaces on the building envelope should be
strengthened in terms of heat transmission
coefficients.
• As the indoors heating systems are
dispositioned, the desired efficiency is not
obtained although the systems are operated for
sufficient time and at sufficient temperature.
• Failure to form necessary heaters in front
of glass surfaces causes radiation asymmetry in
terms of thermal comfort
• The creation of a windbreaker or zoning at
the entrance of the mosque with a dual door
system creates a positive design parameter in
terms of reducing heat losses.
• When the indoor temperature values in the
mosques fail to reach the required temperatures
and when the heating systems are activated from
the floor, they cause radiative asymmetry for the
users in terms of thermal comfort.
• As the mosques have variable usage period
and user number, fast performance heaters are
recommended in addition to floor heating
systems under the carpets.
In this study, heat losses and gains on the
building envelope of two mosques with different
heating, cooling and ventilation systems were
examined considering climate data and thermal
comfort measurements were made according to
the direction of building envelope. This study
aims to transfer knowledge through sampling for
users and designers in design, usage, and
maintenance of the mosques.
Refereces
1. IEA. 2013. Key World Energy Statıstıcs
2012, www.iea.org/publications/.../kwes.pdf
(erişim tarihi: 19.09.2013).
2. M.Yılmaz, “Turkey's Energy Potential and
The Importance of Renewable Energy Sources
in Electric Energy Generation”, Ankara
University Journal of Environmental Sciences,
4,33-54.(2012)
3. N.Eskin, “Determination of Annual Energy
Needs of Non-Residential Buildings”, 9. Teskon
Congress, İzmir. (2009),
4. Turkish Statistical Institute, Culture
Statistics, ISSN 1300-1167, (2013)
5. ANSI/ASHRAE Standard 55-2013,
“Thermal Environmental Conditions for Human
Occupancy”, American National Standards
Institute, ISSN 1041-2336, (2013)
6. BRITISH STANDARDS, “Ergonomics of
The Thermal Environment — Analytical
Determination and İnterpretation of Thermal
Comfort Using Calculation of The PMV and
PPD İndices and Local Thermal Comfort
Criteria”, EN BS ISO 7730:2005, ISBN 0580
472078, (2005)
7. J.V. Hoof, “Forty Years of Fanger’s Model
of Thermal Comfort: Comfort for All?”, Indoor
Air, Singapore, 18,3,(2008)
8. A. B. Atmaca, G. Zorer Gedik,“
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Buildings: Marmara Theology Mosque and Hz.
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