Numerical assessment of night ventilation impact on … · Numerical assessment of night ventilation impact on the thermal comfort of vernacular buildings ... Energy retrofitting
Post on 29-Jul-2018
216 Views
Preview:
Transcript
RESEARCH ARTICLE
Numerical assessment of night ventilation impact on the thermalcomfort of vernacular buildings
Parthena Exizidou1 • Elias Christoforou1 • Paris A. Fokaides2
Received: 17 August 2016 / Accepted: 15 December 2016 / Published online: 7 January 2017
� Springer International Publishing Switzerland 2017
Abstract Night ventilation, is one of the most effective
passive cooling techniques that may contribute to the
improvement of the occupants thermal comfort conditions.
Despite the justified effectiveness of night ventilation, few
studies quantified its influence on the thermal comfort of
vernacular buildings, especially under warm dominant
climates. The aim of this study is the investigation of the
impact of night ventilation on the thermal comfort of
vernacular buildings under summer dominant environ-
mental conditions. The subjects under investigation was
one traditional buildings in the city of Nicosia in Cyprus. In
terms of this study numerical analysis regarding the ther-
mal comfort of the investigated buildings was performed
by employing Energy Plus and the flow solver of Design
Builder. The indoor operative temperature distribution, the
indoor air velocity and a thermal comfort related index
were identified in selected thermal zones of the examined
building using night ventilation. The results of this study
quantified the potential temperature decrease that can result
on vernacular buildings due to the use of night ventilation
and revealed some restrictions with regard to the allowed
percentage of the opening sizes towards achieving optimal
thermal conditions in space. This study aspires to provide
useful insight regarding the importance of humans’
behavior in terms of enabling night ventilation to vernac-
ular buildings, as well as to con-tribute to the ongoing
scientific discussion on this subject.
Keywords Vernacular building � Night ventilation �Computational fluid dynamics (CFD)
List of symbols
Dexp Experimental temperature difference (�C)Dsim Simulated temperature difference (�C)fcl Clothing surface area factor (–)
hc Convective ehat transfer coefficient (W/m2K)
IC Inequality coefficient (–)
lcl Clothing insulation (m2K/W)
M Metabolic rate (W/m2)
Text Ambient temperature (�C)ta Air temperature (�C)tcl Clothing surface temperature (�C)tr Mean radiant temperature (�C)pa Water vapour partial pressure (pa)
Var Relative air velocity (m/s)
W Effective mechanical power (W/m2)
Abbreviations
3D Three dimensional
CFD Computational fluid
dynamics
FVM Finite volume method
Indexes
exp Experimental
sim Simulated
t Time
& Paris A. Fokaides
eng.fp@frederick.ac.cy
1 Frederick Research Center, 7, Filokyprou Str., 1036 Nicosia,
Cyprus
2 School of Engineering, Frederick University, 7, Frederickou
Str., 1036 Nicosia, Cyprus
123
J Build Rehabil (2017) 2:2
https://doi.org/10.1007/s41024-016-0021-6
1 Introduction
Energy retrofitting is an area of the construction industry
which has gained public awareness in the recent years.
More than a quarter of the existing European building stock
was constructed prior to the middle of the last century [1].
These buildings are certainly valued for their cultural and
architectural significance as they reflect the unique char-
acter and identity of European cities, but they were
appointed to address the needs of their original inhabitants.
The difference between original and contemporary occu-
pants’ lifestyle, clothing and activity as well as the thermal
comfort perception itself, is a parameter that needs to be
taken into consideration when assessing the thermal com-
fort of vernacular dwellings today. People’s perceptions of
comfort are influenced by cues from the built environment,
yet humans may adapt the indoor environment, to achieve a
different set of indoor conditions.
Vernacular buildings have evolved through time
acquiring their specific form and layout, through a process
of trial and error. This process implicates the consideration
of multiple environmental and anthropological variables.
The environmental and bioclimatic design elements of
vernacular architecture; amongst which are the considera-
tion of climatic conditions, topography, rational use of
local resources concerning employed materials and com-
plexity of construction was highlighted in previous studies
[2–4]. Passive heating and cooling strategies of vernacular
buildings presumed upon the proper use of materials as
well as buildings’ location and orientation. Other envi-
ronmental approaches though incorporated into the build-
ing design required the active involvement of the user.
Some examples include the shutters operation to control
the direct solar heat gains, the watering of plants to enable
evaporative cooling, and the windows opening to exploit
night ventilation Natural night ventilation is an interesting
passive cooling method in moderate climates. Driven by
wind and stack generated pressures, it cools down the
exposed building structure at night, in which the heat of the
previous day is accumulated [5]. Whilst, the prediction of
occupant behaviour may result to more accurate definitions
of the buildings’ energy requirements, few accounts men-
tion the role of the user in the establishment of thermal
comfort; even fewer studies approach the variant of occu-
pant behaviour when assessing vernacular buildings.
This study aims to provide useful insight regarding the
impact of natural night ventilation on the thermal comfort
of vernacular buildings under summer dominant climatic
conditions. In the following section, a comprehensive lit-
erature review is conducted regarding previous studies
examining the impact of night ventilation to energy con-
sumption of buildings, as well as numerical analysis
practices applied to vernacular buildings to investigate
their thermal comfort. In Sect. 3 the employed methodol-
ogy is presented and Sect. 4 presents and discusses the
results of this study.
2 Literature review
2.1 Night ventilation
Night ventilation, also referred as night cooling, is one of
the more efficient passive cooling techniques that may
contribute to the reduction of the cooling load of buildings
and to the improvement of occupants’ thermal comfort.
Night cooling is based on the circulation of the cool
ambient air in space which results to the decrease of both
the temperature of the building’s structure and of the
indoor air. The cooling potential is mainly based on the
relative difference between the outdoor and indoor tem-
peratures during the night period as well as the air flow
rate, the thermal capacity of the building and the appro-
priate coupling of the thermal mass and the air flow.
Various studies were implemented in the recent parts with
the aim to quantify the impact of night ventilation to build-
ings [6–9]. The majority of these studies regarded office
buildings. Pfafferott et al. [10] conducted experiments in two
offices in order to determine the efficiency of night ventila-
tion dependent on air change rate, solar and internal heat
gains. Corgnati and Kindinis [11] investigated in their study
the activation of building thermal mass by means of outdoor
air ventilation, exalting the effect of night ventilation. In the
study conducted by Geros et al. [12], the efficiency of night
cooling techniques was investigated in 10 different urban
canyons. A typical room under air-conditioned and free-
floating operation was investigated, considered as single-
sided or cross ventilated during the night period. Ramponi
et al. [13] analyzed the cooling effectiveness of night-ven-
tilation for office buildings placed in the center of urban areas
of increased density for three European locations. Night
ventilation rates and energy savings were calculated for the
buildings and compared to the energy demand of the
unventilated buildings. A typical office room was modelled
by Artmann et al. [14]. In his study, the effect of different
parameters (climate, thermal mass, heat gains, air change
rates and heat transfer coefficient) on the effectiveness of
night ventilation was evaluated. Climatic conditions and air
flow rate during night-time ventilation were found to have
the largest effect. Kubota et al. [15], the effectiveness of
night ventilation for residential buildings under warm and
humid climatic conditions was examined. The thermal
environment evaluation showed that night ventilation would
provide better thermal comfort for terraced houses occupants
2 Page 2 of 11 J Build Rehabil (2017) 2:2
123
compared with the other ventilation strategies. Santamouris
et al. [16] calculated the absolute energy contribution of
night ventilation based on energy data from two hundred
fourteen air conditioned residential buildings using night
ventilation techniques. The results showed that the higher the
cooling demand of the building, the higher the potential
contribution of night ventilation under specific boundary
conditions. In Le Dreau et al. [17], heat transfer during 12 h
of discharge by nighttime ventilation in a full scale test room
was investigated. Different ventilation types, air change
rates, temperature differences between the inlet air and the
room, and floor emissivity were examined. Roach et al. [18]
examined the effect in cooling energy of commercial office
buildings from economiser cycles and night time ventilation
when used separately and combined. In the study ofGoethals
et al. [19], a global surrogate-based optimization procedure
was set up to find room/system design solutions which
induce a high convective heat flux during night cooling in a
generic open plan office.
Despite the fact that several studies were conducted
regarding the numerical investigation of night ventilation
impact on the energy consumption of buildings, few studies
were implemented to examine the impact of night venti-
lation to vernacular buildings by means of numerical
simulation.
2.2 Energy performance of vernacular buildings
The numerical investigation of the thermal performance of
vernacular buildings consists a subject that was widely
approached [20–22]. The energy and microclimatic per-
formance of Mediterranean vernacular buildings was
investigated by Cardinale et al. [23]. The study focused on
two types of buildings that are the examples of vernacular
architecture in Southern Italy, namely the Sassi of Matera
and the Trulli of Alberobello. Zhai and Previtali [24] per-
formed an extensive analysis and computer energy model-
ing for a number of representative vernacular architectural
techniques and features summarized for different climatic
regions. The simulation results of the energy models sug-
gested that considering traditions seen in ancient vernacular
architecture as an approach to improving building energy
performance is a worthwhile endeavor and a scientific
guidance can help enhance the performance. In the study
conducted by Nguyen et al. [25], six old houses in rural and
urban areas in Vietnam, were investigated to understand the
climatic design strategies employed and their effectiveness
in maintaining human comfort and health. The results of
this study indicated that vernacular housing in Vietnam is
creatively adapted to the local natural conditions and uses
various climate responsive strategies. Kristianto et al. [26]
investigated the thermal comfort conditions, particularly air
velocity, inside of Minahasa Traditional House, a wooden
raised floor house originated from Tomohon, North Sula-
wesi. Computational fluid dynamic (CFD) analysis was
applied in the study and the effectiveness in creating ther-
mal comfort several variations of openings and stilts height
were evaluated. Simulations results showed that higher
stilts height is higher air velocity inside the test house and
that houses with roof opening has higher internal air
velocity compared to houses with wall opening. The study
conducted by Presetyo et al. [27] aimed to describe Rumah
Lontiok, one of Malay traditional houses and to investigate
its thermal performance. The authors revealed that against
the existing notion, the investigated traditional house pre-
sented a poor thermal performance. The aim of the study
undertaken by Stephan et al. [28] was to evaluate the
thermal inertia in high porosity limestone old buildings in
summer and to determine the impact of a retrofitting solu-
tion on thermal behaviour of these stone buildings. The
analysis of data underlined the advantages of insulation for
thermal inertia on stone buildings. Orehounig and Mahdavi
[29] collected data for five hammans that were used for the
generation of building performance simulation models. The
study showed that the hygrothermal conditions in hammams
vary considerably over time and space and that fairly
stable thermal conditions were achieved. In [30], the
authors conducted a combination of field measurements and
simulations in order to determine the renovation require-
ments. The analysis showed that the improvement of
building service systems and the energy source holds the
largest energy saving potential. Dili et al. [31] compared
and analyzed the thermal performance of traditional and
modern buildings of Kerala, India. Analysis using Biocli-
matic charts revealed that the thermal comfort of traditional
buildings was comparable to contemporary ones.
3 Methodology
3.1 Thermal Comfort Index
In terms of this study, the thermal comfort was determined
according to the well-established ISO 7730:2005 [32]
standard and the PMV index. The PMV index predicts the
mean value of the votes of a large group of persons on the
7-point thermal sensation scale (see Table 1), based on the
Table 1 Seven-point thermal
sensation scale (PMV Index)
[32]
?3 Hot
?2 Warm
?1 Slightly Warm
0 Neutral
-1 Slightly Cool
-2 Cool
-3 Cold
J Build Rehabil (2017) 2:2 Page 3 of 11 2
123
heat balance of the human body. PMV was calculated using
Eqs. 1–4.
PMV ¼ ½0:303� expð�0:036MÞþ 0:028�� fðM�WÞ� 3:05� 10�3�½5733� 6:99�ðM�WÞpa�� 0:42
� ½ðM�WÞ� 58:15� � 1:7� 10�5�M�ð5867� paÞ� 0:0014
�M�ð34� taÞ� 3:96� 10�8� fcl
�½ðtclþ 273Þ4�ðtr þ 273Þ4�� fcl� hc�ðtcl� taÞg
ð1Þ
tcl ¼ 35:7� 0:028� ðM �WÞ � Icl
� f3:96� 10�8 � fcl � ½ðtcl þ 273Þ4 � ðtr þ 273Þ4�þfcl � hc � ðtcl � taÞg
ð2Þ
hc¼2:38 � jtcl� taj0:25 for 2:38 � jtcl� taj0:25[12:1� ffiffiffiffiffiffi
varp
12:1� ffiffiffiffiffiffi
varp
for 2:38 � jtcl� taj0:25\12:1� ffiffiffiffiffiffi
varp
( )
ð3Þ
fcl ¼ 1:00þ 1:290� lcl for lcl\0:078 m2K/W
1:05þ 0:645� lcl for lcl [ 0:078 m2K/W
� �
ð4Þ
The calculation of PMV is based on the metabolic rate
of the occupant (M), the temperatures of the air, the human
surface and the space walls (ta, tcl, tr, respectively) which
are used to quantify heat losses due to conduction (lcl),
radiation (fcl) and convection (hc), the air velocity in space
(Var) and the evaporation (pa) and respiration heat losses.
The metabolic unit used (met) equals to 58.2 W/m2 and the
clothing unit (clo) to 0.155 m2 �C/W. The intervals in
which the PMV is applicable are given in Table 2.
3.2 Numerical analysis process
The calculation of the PMV index requires the definition of
the indoor conditions, including buildings air, radiative and
operative temperatures as well as the air velocity distri-
bution in space. To this end Energy Plus and the flow
solver of Design Builder were employed. Energy Plus is an
energy analysis simulation software tool performing
dynamic sub-hourly thermal load calculations. Basic
important capabilities of Energy Plus comprise.
• sub-hourly time-step simulations for the interaction
between the thermal zones and the environment;
• heat balance based solution technique for building
thermal loads that allows for simultaneous calculation
of radiant and convective effects at both in the interior
and exterior surface during each time step and;
• the use of Conduction Transfer Functions for the
calculation of Transient heat conduction through
building envelope.
Energy Plus is a stand-alone simulation program without
a ‘‘user-friendly’’ graphical interface. In this study Design
Builder was used as a graphical interface. Through Design
Builder and Energy Plus a very fine zoning was performed
and detailed calculation took place at each time step
(Fig. 1). Detailed information regarding geometry, mate-
rials, activity, internal gains, infiltration and natural venti-
lation was integrated into the thermal models for the
accurate representation of the energy performance of the
under-study buildings.
Design Builder also contains a computational fluid
dynamics (CFD) three dimensional (3D) flow solver which
was applied. Design Builder CFD uses finite volume
methods (FVM) to solve a set of partial differential equa-
tions that represent the conservation of mass, the conser-
vation of energy and the second law of Newton
(momentum equation). The equation set comprises the
three velocity component momentum equations, the
Navier–Stokes equations, the energy equation using the k-eturbulence model and equations for turbulence kinetic
energy and the dissipation rate of turbulence kinetic
energy. The simulation input of airtightness building per-
formance is given in Table 3.
The results of the internal CFD analysis were the pre-
diction of the airflow and temperature field. By using a
detailed weather file, the introduction of outside air to the
inside of the building through the position and the size of
the openings was studied and the benefits of natural ven-
tilation, cross ventilation and their effects to the internal
environment temperatures and thermal comfort of occu-
pants were examined.
4 Results and discussion
The subject of investigation was a vernacular building in
the city of Nicosia (Fig. 2). The building is located in the
traditional core of Kaimakli (35�11014.0800N,33�22036.3100E), and it is a typical two-storey courtyard
house with an ‘‘L’’ shape typology. The ground floor
building has a lounge-circulation zone (portico) in North–
South direction. The yard is located in the southern part of
Table 2 PMV parameter intervals in which PMV is applicable [32]
M 46–232 W/m2 (0.8–4 met)
lcl 0–0.31 m2K/W (0–2 clo)
ta 10–30 �Ctr 10–40 �CVar 0–1 m/s
pa 0–2700 Pa
2 Page 4 of 11 J Build Rehabil (2017) 2:2
123
the plot, allowing the exposure to solar heat gains of the
building. The external walls of the building are built with
adobe bricks of 50 cm thickness, and the sloped roof of the
building consists of tiles, MDF plywood, an insulation
layer and wooden beams. In this study, results for Zone 6, a
cross ventilated room next to the ground floor portico of the
building was simulated (Fig. 1). The simulation results
were validated using the inequality coefficient [23], based
Fig. 1 a Design Builder 3D
geometry simulation. b Design
Builder model top view
Table 3 Simulation input of
airtightness building
performance
Openings Walls Floors Roof
Windows Doors External Internal External
Flow coefficient (kg/s.m@1 Pa) 0.00014 0.0014 0.0001 0.003 0.0007 0.0001
Flow exponent 0.65 0.65 0.7 0.75 1 0.7
J Build Rehabil (2017) 2:2 Page 5 of 11 2
123
on measurements provided by the University of Cyprus
research group involved in Biovernacular project [33]
presenting a good agreement The inequality coefficient is
used to validate prediction models used in thermal per-
formance and describes the inequality in the magnitude
domain due to three sources: unequal tendency (mean),
unequal variation (variance) and imperfect co-variation
(co-variance). The resultant coefficient can range in value
between 0 and 1, with 0 indicating a perfect match and 1
denoting no match [34].
IC ¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
1n
Pnt¼0ðDsim;t � Dexp;tÞ2
q
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
1n
Pnt¼0ðDsim;tÞ2
q
þffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
1n
Pnt¼0ðDexp;tÞ2
q ð5Þ
where Dsim;t ¼ ðTint;t � Text;tÞsim the recorded temperature
difference and Dexp;t ¼ ðTint;t � Text;tÞexp the simulated
temperature difference between the interior and the envi-
ronment. Since summer season has the most significant
impact on the total energy consumption of the buildings in
Cyprus, the validation focused on the cooling period. As
night ventilation has an impact on the thermal performance
of buildings during summer, simulations were performed
for the warmest summer months (July, August—see
Table 4). The inequality coefficient for this period was
found to be equal to 0.17.
4.1 Impact of night ventilation on operative
temperature
In Fig. 3 the impact of night ventilation on the operative
temperature of the investigated building is presented. The
windows were considered to be open from 7 pm to 7 am,
whenever the conditions were suitable for night ventilation.
The operative temperature is calculated as the average
value of the air and the radiant temperature. From the given
figure it can be retrieved that night ventilation results to an
average reduction of the operative temperature of 2.7 �C.The maxi-mum temperature reduction during night hours is
5.7 �C. This analysis also revealed the importance of night
ventilation during the night, as the temperature reduction
mainly occurs daily from 8 pm until early in the morning.
Another expected finding is the zeroing of time lag as the
operative temperature minimum in space is found to
overlap with the ambient temperature minimum; for closed
windows, an average time lag of 3 h is observed. The
Fig. 2 Investigated Building: a exterior facades, b interior view of
the ‘‘portico’’ [33]
Table 4 Climatic data for July–August for Nicosia
July August
Dry bulb temperature (�C)Maximum 34.8 34.7
Minimum 15.8 20.4
Daily average 24.6 27.3
Monthly statistics for wind speed (m/s)
Maximum 11.8 10.3
Minimum 0 0
Daily average 4 3.6
Table 5 Reduction of operational temperature for cross and single
ventilation
July August
30% 100% 30% 100%
Cross ventilation
Average 4.2 5.4 4.4 5.7
Max 6.5 7.9 6.5 8.1
Min 2.2 2.7 1.9 2.5
Single ventilation
Average 3.1 4.1 3.2 4.4
Max 5.4 5.9 5.0 6.4
Min 1.1 2.0 1.1 2.0
2 Page 6 of 11 J Build Rehabil (2017) 2:2
123
impact of the night ventilation on theoperative temperature
is summarized in Table 5.
Figure 4 presents the three dimensional operative tem-
perature contour within space for the investigated thermal
zone (9 pm, 01/07). According to this figure, the temperature
gradient in space is much higher in the case of closed win-
dows, resulting to significant temperature differences within
the same space. This is not observed for the opened windows
simulation, where a more homogeneous temperature distri-
bution in space is observed. This finding results due to the
circulation of the cool ambient air in space; the temperature
differences given in Fig. 3 are also confirmed anew.
As it can be retrieved from Fig. 4, the main reason for
the higher temperature decrease is the fact that the inves-
tigated thermal zone is cross ventilated. As expected, cross
ventilation creates some further issues regarding the high
air velocities that will be observed in the building, which
are not in-line with the thermal comfort prerequisites
(Table 1). To this end, a discussion regarding the allowed
opening sizes towards achieving optimal thermal condi-
tions, presented in the following section, is required.
4.2 Indoor air velocity restrictions in night
ventilation
Figure 5 depicts the indoor air velocity contour for the
investigated thermal zone for closed and opened windows
respectively. In the case of the closed windows, the air
motion is attributed to natural convection and thus to the
temperature gradient in space, whereas in the case of open
windows, it is obvious that the air is in motion due to the
entrance of fresh air in the space. As it can be retrieved
from the presented results the air velocity in space, exceeds
1 m/s in the case of the cross ventilated thermal zone. The
maximum air velocities are found as expected near the
Fig. 3 Night ventilation impact
on operative temperature
Fig. 4 a Operative temperature—closed windows. b Operative temperature—open windows
J Build Rehabil (2017) 2:2 Page 7 of 11 2
123
windows. Regarding the closed windows cases, the air
velocity in space has an average velocity of less than
0.1 m/s.
It can be deduced from the calculated air velocities that
although natural night ventilation in cross ventilated rooms
enables the significant reduction of the operative temper-
ature, the indoor air velocities reached are much faster than
those considered within the thermal comfort range. The
maximum allowable indoor air velocities to meet the cor-
responding draught rating categories of the 7730:2005
Standard [32] do not exceed 0.8 m/s. To this end a further
analysis was conducted assuming partly open windows for
the cross ventilated zones. Based on an iterative process, it
was found that 30% windows opening ensured air veloci-
ties in cross ventilated spaces of less than 0.8 m/s. The
reduction of the windows opening area effects as expected
the temperature decrease due to night ventilation.
In Fig. 6 the indoor operative temperature is provided
for fully opened windows and for a 30% opening per-
centage for the case of the cross ventilated investigated
thermal zones. In this figure the actual limitations of night
ventilation with respect to the allowed indoor air velocities
are presented. According to this figure, the average tem-
perature decrease in the case of cross ventilated thermal
zones was 2.2, whereas the maximum temperature differ-
ence in the examined case was 4.7. Compared to the results
given in Sect. 4.1, it is deduced that limitations in indoor
air velocity may reduce the impact of night ventilation up
to 50%.
4.3 Impact of night ventilation on thermal comfort
Figure 7 presents the impact of night ventilation to the
thermal comfort of the investigated space, as calculated
Fig. 5 a Indoor air velocity—closed windows. b Indoor air velocity—open windows
Fig. 6 Night ventilation impact
on operative temperature—30%
windows opening
2 Page 8 of 11 J Build Rehabil (2017) 2:2
123
using the PMV index (see Sect. 3.1). The calculations were
performed by assuming that the air conditioning system
was not in use in both cases. Also a 30% opening per-
centage was considered. The results prove the value of
night ventilation to vernacular buildings in terms of
improving the thermal comfort conditions, as the PMV
index presents a significant decrease. The average PMV
index was found to be 1.1 for the night ventilated thermal
zone, whereas the corresponding number for the non-ven-
tilated zone was 2.25. As it can be deduced from the
results, an average improvement of 51% was achieved in
the investigated thermal zone with the exploitation of night
ventilation.
Although the derived PMV indexes seem to be in the
range of slightly warm to warm in the seven-point thermal
sensation scale, it should be stated that two schools of
thought exist regarding the thermal comfort research area,
namely ‘‘static’’ and ‘‘adaptive’’. The static model meets
the ISO Standard 7730 based on Fanger’s predicted mean
vote (PMV/PPD) [32], as well as the ASHRAE’s Standard
55-Thermal Environmental Conditions for Human Occu-
pancy [35] and it was employed in this study. On the other
hand, the adaptive model, states that factors beyond fun-
damental physics and physiology play an important role in
building occupants’ expectations and thermal preferences.
The way people interact with the environment, their
behaviour changes can modify their thermal expectations
[36, 37].
Figure 8 presents the adaptive thermal comfort levels of
the master bedroom, according to EN 15251 (CYS EN
2007) [38]. For Class II buildings, which is the class tai-
lored for new buildings and renovations, the allowable
maximum difference between this comfort temperature and
the actual indoor operative temperature is ±3 �C. The
analysis of the results showed that the adaptive thermal
comfort levels are mostly satisfied, and only occasionally
Fig. 7 a PMV Index—closed windows. b PMV Index—OPEN WINDOWS
Fig. 8 Adaptive thermal
comfort levels according to EN
15251 (CYS EN 2007)
J Build Rehabil (2017) 2:2 Page 9 of 11 2
123
the thermal conditions are out of the ±3 �C set by the
standard.
5 Conclusions
The aim of this study was the investigation of the impact of
night ventilation on the thermal comfort of vernacular
buildings under warm climatic conditions. To this end, the
thermal behaviour of a vernacular building in the city of
Nicosia was numerically investigated. Energy Plus and the
flow solver of Design Builder were employed. According
to the findings of this study, night ventilation may have a
significant impact on the temperature and on the thermal
comfort levels in vernacular buildings. Some restrictions
with regard to the opening percentage were revealed,
resulting from the al-lowed air velocities in space. The
temperature decrease due to natural ventilation was found
to reduce to a factor of 2, the air velocity being within
acceptable levels. Regarding the thermal comfort levels,
these were found to be improved on an average percentage
of 26% with the use of night ventilation. Although the
thermal comfort according to the PMV scale was consid-
ered to be in the slightly warm levels, the implementation
of an adaptive model, would have revealed a better per-
formance of night ventilated spaces.
Acknowledgments Authors are indebted to the research project
‘‘Innovative methods for protection and conservation of sustainable
design elements of vernacular architecture in the historic centre of
Nicosia—Biovernacular’’ for the financial support of this work.
Biovernacular was funded by the European Regional Development
Fund and the Republic of Cyprus through the Research Promotion
Foundation (Project Technological Development and Innovation
De9rlg 2009–2010, AMHQXPIRSIJER/AMHQX/0609/BIE).
References
1. European Commission. The energy-efficient buildings PPP.
Internet] 2013 [cited 2014]; Available from http://ec.europa.eu/
research/industrial_technologies/en-ergy-efficient-buildings_en.
html
2. Balaras CA, Gaglia AG, Georgopoulou E, Mirasgedis S, Serafidis
Y, Lalas DP (2007) European residential buildings and empirical
assessment of the Hellenic building stock, energy consumption,
emissions and potential energy savings. Build Environ
42:1298–1314
3. Vissilia AM (2009) Evaluation of a sustainable Greek vernacular
settlement and its land-scape: architectural typology and building
physics. Build Environ 44:1095–1106
4. Singh MK, Mahapatra S, Atreya SK (2009) Bioclimatism and
vernacular architecture of north-east India. Build Environ
44:878–888
5. Breesch H, Janssens A. Reliable design of natural night ventila-
tion using building simulation. Thermal performance of the
exterior envelopes of whole buildings X, proceedings. Atlanta,
GA, USA: American Society of Heating, Refrigerating and Air-
Conditioning Engineers; 2007
6. Blondeau P, Sperandio M, Allard F (1997) Night ventilation for
building cooling in summer. Sol Energy 61:327–335
7. Kolokotroni M, Aronis A (1999) Cooling-energy reduction in air-
conditioned offices by using night ventilation. Appl Energy
63:241–253
8. Geros V, Santamouris M, Tsangrasoulis A, Guarracino G (1999)
Experimental evaluation of night ventilation phenomena. Energy
Build 29:141–154
9. Artmann N, Jensen RL, Manz H, Heiselberg P (2010) Experi-
mental investigation of heat transfer during night-time ventila-
tion. Energy Build 42:366–374
10. Pfafferott J, Herkel S, Jaschke M (2003) Design of passive
cooling by night ventilation: evaluation of a parametric model
and building simulation with measurements. Energy Build
35:1129–1143
11. Corgnati SP, Kindinis A (2007) Thermal mass activation by
hollow core slab coupled with night ventilation to reduce summer
cooling loads. Build Environ 42:3285–3297
12. Geros V, Santamouris M, Karatasou S, Tsangrasoulis A,
Papanikolaou N, Guarracino G (2005) On the cooling potential of
night ventilation techniques in the urban environment. Energy
Build 37:243–257
13. Ramponi R, Gaetani I, Angelotti A (2014) Influence of the urban
environment on the effectiveness of natural night-ventilation of
an office building. Energy Build 78:25–34
14. Artmann N, Manz H, Heiselberg P (2008) Parameter study on
performance of building cooling by night-time ventilation.
Renewable Energy 33:2589–2598
15. Kubota T, Chyee DTH, Ahmad S (2009) The effects of night
ventilation technique on in-door thermal environment for resi-
dential buildings in hot-humid climate of Malaysia. Energy Build
41:829–839
16. Santamouris M, Sfakianaki A, Pavlou K (2010) On the efficiency
of night ventilation tech-niques applied to residential buildings.
Energy Build 42:1309–1313
17. Le Dreau J, Heiselberg P, Jensen RL (2013) Experimental
investigation of convective heat transfer during night cooling
with different ventilation systems and surface emissivities.
Energy Build 61:308–317
18. Roach P, Bruno F, Belusko M (2013) Modelling the cooling
energy of night ventilation and economizer strategies on facade
selection of commercial buildings. Energy Build 66:562–570
19. Goethals K, Couckuyt I, Dhaene T, Janssens A (2012) Sensitivity
of night cooling performance to room/system design: surrogate
models based on CFD. Build Environ 58:23–36
20. Al-Motawakel MK, Probert SD, Norton B (1986) Thermal
behaviours of vernacular buildings in the Yemen Arab Republic.
Appl Energ 24:245–276
21. Borong L, Gang T, Peng W, Ling S, Yingxin Z, Guangkui Z
(2004) Study on the thermal performance of the Chinese tradi-
tional vernacular dwellings in Summer. Energy Build 36:73–79
22. Cardinale T, Colapietro D, Cardinale N, Fatiguso F (2013)
Evaluation of the efficacy of traditional recovery interventions in
historical buildings. A new selection methodology. Energy Pro-
cedia 40:515–524
23. Cardinale N, Rospi G, Stefanizzi P (2013) Energy and micro-
climatic performance of Mediterranean vernacular buildings: the
Sassi district of Matera and the Trulli district of Alberobello.
Build Environ 59:590–598
24. Zhai ZJ, Previtali J (2010) Ancient vernacular architecture:
characteristics categorization and energy performance evaluation.
Energ Build 42:357–365
25. Nguyen A, Tran Q, Tran D, Reiter S (2011) An investigation on
climate responsive design strategies of vernacular housing in
Vietnam. Build Environ 46:2088–2106
2 Page 10 of 11 J Build Rehabil (2017) 2:2
123
26. Kristianto MA, Utama NA, Fathoni AM (2014) Analyzing indoor
environment of Minahasa traditional house using CFD. Procedia
Environ Sci 20:172–179
27. Presetyo YH, Alfta MNF, Pasaribu AR (2014) Typology of
Malay traditional house Rumah Lontiok and its response to the
thermal environment. Procedia Environ Sci 20:162–171
28. Stephan E, Cantin R, Caucheteux A, Tasca-Guernouti S, Michel
P (2014) Experimental assessment of thermal inertia in insulated
and non-insulated old limestone buildings. Build Environ
80:241–248
29. Orehounig K, Mahdavi A (2011) Energy performance of tradi-
tional bath buildings. Energ Buildings 43:2442–2448
30. Alev U, Eskola L, Arumagi E, Jokisalo J, Donarelli A, Siren K
et al (2014) Renovation alter-natives to improve energy perfor-
mance of historic rural houses in the Baltic Sea region. Energy
Build 77:58–66
31. Dili AS, Naseer MA, Varghese TZ (2011) Passive control
methods for a comfortable indoor environment: comparative
investigation of traditional and modern architecture of Kerala in
summer. Energ Buildings 43:653–664
32. ISO 7730:2005(E) Ergonomics of the thermal environment—
analytical determination and interpretation of thermal comfort
using calculation of the PMV and PPD indices and local thermal
comfort criteria
33. Innovative methods for protection and conservation of sustain-
able design elements of vernacular architecture in the historic
centre of Nicosia—Biovernacular [cited 2014]; Available from
http://biovernacular.ac.cy
34. Fokaides PA, Christoforou E, Ilic M, Papadopoulos A (2016)
Performance of a Passive House under subtropical climatic
conditions. Energy Build 133:14–31
35. ASHRAE (1992) Standard 55—thermal environmental condi-
tions for human occupancy. ASHRAE Inc, Atlanta
36. De Dear R, Brager G, Cooper D (1997) Developing an adaptive
model of thermal comfort and preference—final report on
ASHRAE RP-884, Sydney, MRL
37. De Dear RJ, Brager GS (2002) Thermal comfort in naturally
ventilated buildings: revisions to ASHRAE Standard 55. Energy
Build 34:549–561
38. CYS EN (2007) 15251, Indoor environmental input parameters
for design and assessment of energy performance of buildings
addressing indoor air quality, thermal environment, lighting and
acoustics. European Committee for Standardization, Brussels
J Build Rehabil (2017) 2:2 Page 11 of 11 2
123
top related