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Abstract:
Natural ventilation, being the
most environmentally friendly form of ventilation is very important in
improving thermal comfort and indoor air quality in buildings. With the
advancement in technology, there have been introduced many mechanical ways of
ventilation as well. However, natural ventilation strategies hold many
advantages over such mechanical solutions such as lower initial and maintenance
costs. Due to the hot and humid climate of Famagusta, natural ventilation is
therefore an effective way of improving thermal comfort and indoor air quality
in residential buildings. This study aims to determine the most effective means
of achieving natural ventilation and the most ideal orientation for residential
buildings in the city of Famagusta, North Cyprus during the summer and winter
periods.

 

Keywords: Famagusta,
Hot and Humid Climate, Natural Ventilation, Residential buildings, Thermal
Comfort
With
the increase in the number of residential buildings being brought up to cater
for the needs of the locals and foreigners in Famagusta, it is important to
ensure a comfortable living environment and a desirable level of thermal
comfort within these internal spaces. Natural
ventilation is an ideal and suitable means in creating the desired levels of
thermal comfort in indoor environments especially in places such as Famagusta
where the climate is hot and humid. Although, new technological advancements have
brought about new ways of ventilation such as mechanical ventilation in
achieving similar results, natural ventilation strategy still holds various
advantages over the former such as the incredibly low comparative first and
operating costs. Secondly, natural ventilation generates cleaner air, therefore
more sustainable. Installing mechanical systems in order to ventilate spaces in
buildings adds up to the expenses of construction as well as use of electric
power to generate these systems. Natural
ventilation uses simple principles obtained from nature. It is achieved using
natural forces such as either wind or thermal buoyancy or in some cases both of
them in order to regulate the building’s indoor climate. Such forces are
created by differences in temperature between the inside and outside of the
building, thermal displacement within the building and prevailing winds.The
principle behind natural ventilation is that warm air rises and escapes the
internal environment through openings and is replaced by cool air from outside,
thereby lowering the internal temperature in the building.  Use
of openings and windows in buildings can control the air change in order to
achieve the desired levels of thermal comfort for the users. Simply opening and
closing the windows would achieve the natural ventilation depending on the
internal and external conditions.Two
main strategies are used to achieve natural ventilation. These are: cross
ventilation and stack ventilation. 5.1
Cross Ventilation

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Cross ventilation is driven
by wind. The wind coming from the windward side creates a positive pressure at
this point and the wind moving away from the leeward side creates a
low-pressure zone at that point. This therefore creates a difference in
pressure levels at the two sides and thereby opening windows at these two ends
would force the air to move through the building due to pressure level
difference. Depending on the placement, size and location of the openings, a
number of results can be achieved.5.2
Stack Ventilation

Stack
ventilation on the other hand is driven by thermal buoyancy. The difference in
temperature of the inside air and the outside makes this work. Since warm air
is lighter than cold air, it moves upwards. When windows are opened at
different levels, the warm air inside the building would leave out through the
top opening and the cool air from outside would enter the building through the
lower opening to replace it.The
elements of natural ventilation include openings on facades (windows),
chimneys, double-skin facades, atriums and ventilation chambers. It is possible
to integrate more than one of these elements into a building depending on the
form and organization as well as the design strategy and the environmental
factors.

The
keys to effective natural ventilation are the building orientation, the sizing
and placing of the openings. The location and size of the openings is important
on the windward and leeward side as the air flow is affected by such factors.
Air flows from the windward side to the leeward side (positive to negative
pressure zone).

Having
smaller inlet openings than the outlet openings increases the speed of air
flow. This is due to Venturi effect. This principle can be used to achieve the
desirable levels of user comfort in buildings through natural ventilation.For
buildings in hot-humid climates, it is recommended to create openings in
different walls to allow for cross ventilation for all rooms. 5 This would
enable the free flow of air throughout all rooms in the building.

Window
sizes and location would determine the success of the ventilation strategy in a
building. The openings on either side of the building enable cross ventilation
by creating different pressure zones. The factors that would affect the air
flow therefore include the size, location and orientation of these openings.

The average interior air velocity is
subordinate to the size and location of the openings, the angle between the
wind direction and the inlets and velocity of the exterior free wind. 1

 

Acceptable
air flow velocity depends on the temperature and humidity of the environment.
At temperatures below 33?C, increase in air velocity increases the thermal
comfort level. 4

 

During
the hot season, thermal comfort ventilation could have either of the following
aspects; firstly, when the outside temperature is lower than the indoor
temperature, ventilation can cool down the indoor air by replacing the outside
air. It can also cool down the building structure. The second aspect is when
the outside temperature is higher, ventilation can cause direct cooling on the
human body for evaporation and convection.

There
are two ways to enhance the level of human comfort in natural ventilation:
direct and indirect physiological effects. These are known as ‘Comfort
Ventilation’, which involves more wind through openings to increase the indoor
airflow and results in the occupants feeling cooler. Direct approach is
ventilative cooling and indirect approach is to improve the level of comfort by
ventilating the building at night to cool down the interior, which is known as
‘Nocturnal Ventilative Cooling’. 3

Comfort
ventilation is mainly applicable to regions and seasons when the outdoor
maximum air temperature does not exceed 28-32?C and where the diurnal temperature
range is less than 10?C. 4Two
residential buildings in Famagusta have been analysed as a part of the study. These buildings are being studied in their
location in the sites, the orientation towards the wind and sun, the placement
of windows, the plan design and placement of interior spaces. The locations and
facades of the sample buildings are shown in the figures below.The
research is based on observation and creating simulations using CoolVent
software. The method combines energy and airflow calculations to simulate the
results for the average climate conditions of Famagusta for the Summer and
Winter period using the apartment buildings chosen for the study. In this
study, residential buildings with different window types and sizes are oriented
in different directions and the results generated.

The plans for the
residential buildings used for the study are drawn and the buildings 3D
modelled (shown in Fig. 6 and Fig. 7.) The simulations are done for the average
climate conditions for the two seasons. The buildings’ internal spaces are
categorized into different zones.The
facades for the apartment buildings being studied are very simple with window openings as the only natural
ventilation strategy element. Most of the residential buildings in the areas consist
of four to six storeys. The buildings analysed for the study are both 5
storeys. Both the buildings are oriented towards the North-East direction in
their respective site locations and the general shapes of the buildings is
rectangular. They consist of two and four apartment units on each floor and
have been designed symmetrically. Most of the residential buildings in the
surrounding are built very close to each other and this sometimes affects the
natural ventilation.

The results from the Summer and Winter
simulations have been shown in a zonal form. The residential buildings have
been divided into various zones which have been numbered. The results show the
rate of airflow in these zones and spaces in the buildings and the general
thermal comfort level for the occupants.

Figure 8 below shows the results of the
simulation for Uzun 10 Apartments during the Summer and Winter seasons when the
building is oriented in the North-East direction.The blue colour on the zones indicate the
smallest pressure loss while the red indicates the largest pressure loss in
these spaces. The maximum and minimum air flow rates are indicated for a
particular space within the zones. The assumption is that there are no
buildings right next to the apartments being studied.

As seen from the results generated in
Figure 8 above, during the Summer, the spaces on the South façade would heat up
due to the direct sun rays through the windows.

When the building orientation is changed to
the South direction, the following results (Figure 9) are seen.The
opposite results are achieved when the building orientation is mirrored in the
opposite South direction as seen in the figure above. The interior spaces on
the south façade again heat up during the Summer season while it is cooler
during the Winter.

The
next step was to simulate the results for Uzun 12 Apartments for the Summer and
Winter season in comparison with the other.

Figure 9 below shows the results of the
simulation for Uzun 12 Apartments during the Summer and Winter seasons when the
building is oriented in the North-East direction.When
the building’s original orientation in the North-East direction is maintained,
it is observed that the ventilation and thermal comfort levels are satisfactory
both in the Summer and Winter periods. Since the building has just two
apartment units on each floor as compared to the four units in the Uzun 10
apartment building, the units have both a South and North façade. This enables
a convenient planning of interior spaces to allow for cross ventilation within
the units and also sunshine.

When
the building is oriented towards the South direction, the results in Figure 11
below are achieved.From the results, the changes can be noted
when the building orientation is turned from the North East to the South
direction.

During the Summer period, ventilation in
the building would seem satisfactory due to the windows on the South-East, and
East façades of the building.

However, the rooms on the south façade
become very hot during the Summer season due to the direct sun through the
windows. Due to some of these interior spaces heating up during the Summer
period, it would be advisable to install sun-shading devices on the south
facing façade windows so as to avoid excessive heating of these spaces.

From the research, it is determined that Uzun 12
apartment building is better ventilated and provides a more suitable thermal
comfort level for the occupants. This is mainly due to having two units per
floor thereby each unit having both a north and south orientation.For
residential apartments in Famagusta, it is important to have a floor plan in a
way which would enable the units to have both a north and south orientation to
achieve cross ventilation in summer and to have access to the sun’s rays in
winter. Also, the space organisation for the common spaces and most used spaces
in the building have to be planned with careful consideration to the sun and
wind direction to enable proper ventilation and keep the spaces warm during the
winter period thereby maintaining a suitable thermal comfort level for the
occupants.

In
cases where it would not possible to have cross ventilation in the apartments,
the inclusion of a solar chimney would be a good alternative method of
circulating the air on all the floors on hot days in Summer.

Bigger window sizes could also help in
achieving better ventilation in the building during the Summer as well.

Orientation of the buildings and the
distance between them should be organised in a way that they do not block each
other from south and east wind direction and south sun radiation. 

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