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Energy & Buildings 175 (2018) 30–47
Contents lists available at ScienceDirect
Energy & Buildings
journal homepage: www.elsevier.com/locate/enbuild
Passive cooling & climate responsive façade design
Exploring the limits of passive cooling strategies to improve the
performance of commercial buildings in warm climates
Alejandro Prieto
a , ∗, Ulrich Knaack
a
, Thomas Auer
b
, Tillmann Klein
a
a
Delft University of Technology, Faculty of Architecture and the Built Environment, Department of Architectural Engineering +Technology, Architectural
Façades & Products Research Group, Julianalaan 134, Delft 2628BL, The Netherlands
b
Tech nica l University of Munich, Department of Architecture, Chair of Building Technology and Climate Responsive Design, Arcisstrae Be 21, Munich 80333,
Germany
a r t i c l e i n f o
Article history:
Received 3 October 2017
Revised 3 May 2018
Accepted 9 June 2018
Available online 23 July 2018
Keywo rds:
Passive cooling
Energy savings
Commercial buildings
Shading
Window-to-wall ratio
Glazing
Ventilation
a b s t r a c t
Cooling demands of commercial buildings present a relevant challenge for a sustainable future. They
account for over half of the overall energy needs for the operation of an average office building in warm
climates, and this situation is expected to become more pressing due to increasing temperatures in cities
worldwide. To tackle this issue, it is widely agreed that the application of passive strategies should be the
first step in the design of energy efficient buildings, only using active equipment if it is truly necessary.
Nonetheless, there is still further need for information regarding the potential limits derived from their
application.
This paper explores the effectiveness of selected passive cooling strategies in commercial buildings
from warm climates, defining performance ranges based on the assessment of multiple scenarios and
climate contexts. This task was conducted through the statistical analysis of results from documented re-
search experiences, to define overall ranges and boundary conditions; and through software simulation
of selected parameters to isolate their impact under a controlled experimental setup. General findings
showed that the mere application of passive strategies is not enough to guarantee relevant savings. Their
effectiveness was conditioned to both the harshness of a given climate and different building parame-
ters. Specific recommendations were also discussed for the selected passive strategies considered in the
evaluation.
© 2018 The Authors. Published by Elsevier B.V.
This is an open access article under the CC BY license. ( http://creativecommons.org/licenses/by/4.0/ )
1. Introduction
The energy required to provide cooling for commercial build-
ings is an issue of concern in the current global agenda for sus-
tainability. It has been stated that refrigeration and air condition-
ing account for about 15% of the total electricity consumption in
the world [1] , while cooling may be responsible for over half of the
overall energy needs for the operation of an average office build-
ing in warm climates [2] . The relevance of cooling demands in
commercial buildings responds to high internal gains (occupation
density and equipment) in general, which is aggravated by the im-
pact of solar radiation in commonly lightweight and highly glazed
façades [3] . On a global scale, the relevance of cooling demands
will keep increasing, considering climate change and the impact
∗Correspondence author.
E-mail address: A.I.PrietoHoces@tudelft.nl (A. Prieto).
of fast growing economies from warm climates, such as India and
China, on energy consumption projections for the next decades
[4–6] .
Several initiatives have been put in place to tackle this sit-
uation, focusing on the energy savings potential of the building
sector. Good practices and benchmarks are being extensively pro-
moted for referential purposes [7,8] , while regulation is being en-
forced to reduce the operational energy demands in buildings [9] .
To accomplish this goal, it is widely agreed that the first step in
the design of an energy efficient building should be the application
of passive strategies under a climate responsive design approach
[10–12] , before considering mechanical equipment driven by fossil
fuels. Therefore, understanding the potential benefits from passive
design strategies and the limits for their application has become
a relevant research field, particularly concerning façade design, as
the main filtering layer between outside and inside [13] .
https://doi.org/10.1016/j.enbuild.2018.06.016
0378-7788/© 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license. ( http://creativecommons.org/licenses/by/4.0/ )
A. Prieto et al. / Energy & Buildings 175 (2018) 30–47 31
The performance of passive cooling strategies in office build-
ings has been increasingly studied over the last couple of decades,
mostly through the use of computer simulations [14] . Most ex-
periences focus on specialised evaluations of one or more strate-
gies, such as ventilation or solar control, under selected param-
eters. Regarding ventilation, relevant examples are the studies
carried out by Kolokotroni et al. [15,16] on night ventilation per-
formance and the extensive studies carried out by Gratia and De
Herde on the potential for natural ventilation on double-skin fa-
cades [17,18] . Solar control studies have mostly focused on design
optimisation of sun shading components to improve their perfor-
mance, through multi-variable analysis and parametric design [19–
21] . Although these experiences are regarded as highly valuable
referential information, their results are constrained to the partic-
ularities defined for each evaluation setup, namely climate context
or assumptions from the base model; hindering their direct trans-
lation under different conditions. On the other hand, it is possible
to find more comprehensive approaches that explore the potential
of different passive cooling strategies in various climates, through-
out the review of climate factors [22,23] , or by developing and
testing multi-objective assessment tools [24,25] . Nonetheless, these
studies mainly focus on the general suitability of passive strategies
based on climatic considerations, but do not fully explore their po-
tential limits and expected performance considering particularities
of the building.
This paper discusses the expected performance of selected pas-
sive cooling strategies in commercial buildings from warm cli-
mates, to explore the extents of passive design optimisation under
varying conditions. Hence, the main goal of the article is to de-
fine ranges of performance for each addressed strategy, in terms of
energy savings potential, identifying borderline situations and opti-
mal scenarios based on previous research experiences. The decision
to use results from the literature as main information source was
driven by the desire to contrast multiple scenarios and parameters,
to account for variability present on real conditions. A secondary
reason was an aspiration to organise valuable scientific data in a
systematic way in order to provide useful referential guidelines for
passive design of commercial buildings, instead of generating re-
dundant new data. The review and statistical analysis of the infor-
mation was followed by a controlled series of simulations in order
to explore certain aspects in more detail.
Therefore, the assessment was structured in two main con-
secutive stages: first, a review of research experiences was con-
ducted, to establish performance ranges based on available infor-
mation; followed by a sensitivity analysis to evaluate the different
strategies in a controlled environment. The review served as ref-
erential information considering a wide array of variables, cases
and contexts, while the sensibility analysis was used to under-
stand the potential impact of selected variables and their inter-
action, on the cooling savings for a particular case in humid and
dry warm climates. The variables for the detailed analysis were se-
lected from the referential information gathered through the re-
view of research experiences. The results from each stage are dis-
cussed individually, while the boundaries and defined parameters
for the overall assessment are presented on a separate section
dealing with material and methods.
1.1. Passive cooling: definitions and selection of strategies to be
evaluated
Passive cooling is commonly understood as a set of natural pro-
cesses and techniques to reduce indoor temperatures, in opposition
to the use of ‘active’ mechanical equipment. Nonetheless, this bi-
nary distinction present problems in practice, addressed by several
authors when stating that the use of minor mechanical equipment
such as fans and pumps is allowed under the term ‘passive’ if their
application might result in a better performance [26] . Therefore, it
is possible to find two distinct groups within passive cooling con-
cepts, based on the use of auxiliary equipment. On the one hand,
strategies such as solar control, building layout, orientation, and
control of internal heat sources, are presented in the literature as
‘bioclimatic design strategies’ [26] , ‘basic building design’ [11] , or
simply ‘passive cooling’ [27] . On the other hand, concepts which
benefit by the use of pumps or fans, such as geothermal, evapo-
rative and radiative cooling or night flush ventilation, are defined
as ‘natural cooling’ [27] or most commonly ‘passive cooling sys-
tems’ [11,26,28] . Nevertheless, the common attribute of all men-
tioned strategies is that they are driven by low valued energy, in
the form of environmental heat sources and sinks (low-exergy in-
stead of high-exergy sources such as electricity) [29,30] . Thus, an
extra layer in the discussion was added by Kalz and Pfafferott by
categorising the discussed groups in ‘passive low-ex’ and ‘active
low-ex’ cooling systems, in a declared effort to propose less am-
biguous terminology [31] .
From a physics standpoint, cooling strategies are also cate-
gorised in the literature according to the way they handle heat, ba-
sically distinguishing heat avoidance/protection, heat modulation,
and heat dissipation principles and according strategies [27,32] .
The fact that heat modulation techniques do not reduce cooling
loads by themselves has been discussed by some authors, choosing
to present them as a complement of heat dissipation/heat rejec-
tion cooling strategies [11,26] , storing heat indoors to be released
outside at a more convenient time. Hence, basic passive cooling
principles seek to primarily avoid unwanted heat, while dissipating
the surplus throughout environmental heat sinks. These two sets of
principles define different technical possibilities, which match the
distinction between building design strategies and passive systems,
allowing a comprehensive categorisation of passive cooling princi-
ples ( Fig. 1 ).
Fig. 1 shows an overview of passive cooling strategies and sys-
tems mentioned in the literature, categorised according to the dis-
cussed variables. Consequentially, two main groups were identi-
fied: passive design strategies and passive cooling systems, dealing
with heat avoidance and heat dissipation respectively. The differ-
ent possibilities are shown within the groups, with reference to the
authors who mentioned them. Moreover, the overview also consid-
ers indirect strategies, which do not particularly provide a cooling
effect, but their correct application could result on reduced cool-
ing demands (use of daylight, air-tightness), or serve as a com-
plement for heat dissipation strategies (thermal mass, PCM stor-
age). Cooling strategies are further categorised within the main
groups, in terms of their working principles. Hence, passive sys-
tems are classified according to the heat sinks they employ, being
air, earth, water or sky; and passive design strategies are distin-
guished by their effect at whole building or site design level, man-
agement of internal heat gains, or design decisions concerning heat
transfer through the façade, either through opaque or transparent
components.
For purposes of the analysis, it was decided to focus on pas-
sive low-ex cooling strategies, as they represent the first step of
building design optimisation, before adding additional equipment.
Furthermore, the evaluation sought to consider relevant heat pre-
vention and heat dissipation strategies for commercial buildings,
so a second decision was to focus on solar control and ventilation
cooling strategies. On the one hand, diurnal and nocturnal ventila-
tion have been proven to be effective and simple heat dissipation
strategies, driven either by natural or mechanical means. Of course,
in the latter case, the potential operational benefits derived from
using fans have to surpass the inconvenient extra energy required
for their operation. On the other hand, the impact of solar radia-
tion on the cooling demands of commercial buildings is a partic-
ularly important aspect to consider in warm climates. Moreover,
32 A. Prieto et al. / Energy & Buildings 175 (2018) 30–47
Fig. 1. Categorisation of passive cooling principles based on the literature review.
façade design is specially determinant in urban contexts, where
site restrictions and orientations are set beforehand, so the po-
tential for passive optimisation falls on an adequate design of the
building envelope, according to the particular climate context, with
emphasis on the treatment of its transparent components.
2. Strategy and methods
As explained before, the evaluation was conducted in two se-
quential steps. First, a review of performance results from previ-
ous research experiences was carried out, to define performance
ranges for each passive cooling strategy considering multiple sce-
narios. This was followed by a sensitivity analysis through the use
of an energy simulation software, to discuss and compare the gen-
eral results under a controlled experimental setup, in order to as-
sess the impact of certain variables on the expected cooling perfor-
mance. The methods, boundary conditions and parameters set for
each evaluation stage are presented separately.
2.1. Review of passive cooling research experiences
Published results in peer reviewed scientific articles were
considered as source material for the evaluation. The articles were
selected from several journal online databases, following initial
search queries to explore the field, presented and discussed in
an earlier work [14] . The review considered research experiences
conducted on cooling dominated climates in tropical, dry and tem-
perate zones (class A, B and C in Koppen’s classification), focusing
exclusively on passive cooling. As mentioned before, the strategies
considered in the evaluation were ventilation and solar control
strategies, namely shading, glazing type, and window-to-wall
ratio.
Given that the goal of the review was to define performance
ranges for several cooling strategies, it was necessary to consider
the same type of output from the findings to allow for compar-
isons. Because of its referential value for design purposes, cooling
demands savings was chosen as the unit for comparison, under-
stood as the reduction (in percentage) from the cooling demands
of a base case scenario, after the application of a particular cooling
strategy. This decision directly influenced the article selection pro-
cess, considering research experiences which analysed the perfor-
mance of diverse cooling strategies in terms of cooling demands,
instead of temperature differential, or perceived thermal comfort.
In some cases, cooling savings were directly given, while in some
others were calculated based on the reported total cooling de-
mands of several scenarios before and after intervention. Moreover,
the goal was to assess the reduction potential of different cooling
strategies, so it was a prerequisite to be able to isolate their spe-
cific influence from the available information published in the pa-
pers. Hence, the research methods and published data had to be
comprehensive enough to allow for correct interpretation. As an
additional fact, all selected articles used energy simulation soft-
ware for evaluation purposes, clearly detailing the experimental
setup. So, in all selected research experiences, it was possible to
define a primary strategy being tested, in which case only parame-
ters related with that particular strategy were modified from base
case to the intervened scenario. In some cases, a secondary strat-
egy was identified, but they were regarded as auxiliary to the main
strategy evaluated, such as the increase of thermal mass to further
improve night ventilation strategies. The possible impact of these
secondary strategies on cooling demand reduction was considered
when discussing the results.
Table 1 shows the selected articles for the review, based on the
criteria discussed above. Besides references, the table shows the
climate zones referred in each document and the passive cooling
strategies evaluated by the authors. These articles were reviewed
to generate a database which considered not only the reported re-
sults in terms of cooling demand savings, but also relevant infor-
mation about the experimental setups and parameters set by the
researchers. The database consists of 526 rows of data, from 41 sci-
entific articles [33–73] . Each data row in the database corresponds
to one reported experiment, based on the evaluation of the effect
of a particular parameter in the performance of a passive strat-
egy in a given climatic context. This meant that if the evaluation
was carried out in more than one climate, or multiple strategies
were analysed, this resulted in separated data rows for each one
of the cases. Likewise, if several parameters were evaluated for a
particular strategy, such as the performance of different shading
types, it also resulted on separate rows for each one of the defined
types, associated with each different reported cooling demand sav-
ings. Results from evaluations conducted on cold climates were not
A. Prieto et al. / Energy & Buildings 175 (2018) 30–47 33
Tabl e 1
Articles considered in the review, with climate zones and passive cooling strategies evaluated by the authors.
considered in the databased, even if they were reported in the re-
viewed articles.
The database was categorised and explored through descriptive
analysis techniques with the use of IBM SPSS Statistics software.
An initial overview of the sample was conducted, to characterise
the gathered information and present the array of research experi-
ences considered in the database, accounting for climate variations
and the share of each passive cooling strategy in the total amount
of data rows ( n = 526). The graph in Fig. 2 shows the amount of
results per climate context, classified in four groups: tropical (Af,
Am, Aw), dry (BWh, BWk, BSh, BSk), humid temperate (Cfb, Cwb,
Cfa, CWa), and dry temperate climates (Csa, Csb), representing 16%,
21%, 21% and 42% of the total sample respectively. Considering hu-
midity as a defining parameter, warm dry climates comprehend
63% of the sample ( n = 331), while warm humid climates account
for the remaining 37% ( n = 195).
The composition of the sample in terms of selected passive
strategies is shown in Fig. 3 , considering an initial distinction be-
tween warm dry and warm humid climates. It is possible to see
that even though the sample considers more research conducted
on dry climates, all strategies are covered in both main climate
groups. Performance ranges for each passive cooling strategy are
defined and discussed separately, in Section 3 , considering climate
variation. Furthermore, relevant experiences are discussed in detail,
identifying average performance values and borderline scenarios,
to assess expected savings from each strategy and reported limits
of their impact in different warm climates.
2.2. Sensitivity analysis of passive cooling strategies
The sensitivity analysis sought to complement the results from
the review with results obtained under a controlled setup, isolat-
ing the impact of the evaluated strategies on two different refer-
ence buildings, located on representative cities from selected warm
climates. While the review aimed to provide overall performance
ranges considering a high variation of scenarios, the sensitivity
analysis allowed to directly compare cooling savings potential of
the evaluated strategies and possible relations between them on
two reference cases. Furthermore, it allowed to compare not only
cooling reduction in terms of percentage, but also discuss brute
cooling demands per square meter before and after the application
of each strategy.
DesignBuilder v4.7 was used for the analysis, as the graphi-
cal interface of EnergyPlus v8.3. The base model consisted of a
34 A. Prieto et al. / Energy & Buildings 175 (2018) 30–47
Fig. 2. Number of reviewed results per climate context.
Fig. 3. Number of results per strategy and main climate groups.
Fig. 4. Office floor plan used as base case.
complete office floor of 2.7 m high and a plenum of 0.7 m, with
perimeter offices of 4 ×4 m each as shown in Fig. 4 . Only high-
lighted offices were considered in the analysis, using their cool-
ing demand values to define a floor average as unit for compari-
son during the evaluation. Basic building parameters and internal
heat gains were set based on referential values commonly used in
the reviewed research experiences. Hence, occupancy was set at
0.1 people/m
2
, equipment loads at 11. 77 W/m
2 and infiltration rate
was set at 0.2 air changes per hour (ach). Ventilation was kept at
a minimum rate for hygienic purposes (10l/s per person), while
lighting was controlled, with a target illuminance of 400 lx and
a lighting power density of 3 W/m
2 for 100 lx. Thermal comfort
ranges considered a maximum temperature of 26 °C and relative
humidity between 25 and 55%.
To define the scenarios to be simulated, two conditions were
set for each passive cooling strategy: an initial condition (0),
where the strategy is not applied in the building, and a sec-
ond condition (1) , considering its application by changing a spe-
cific parameter, as shown in Table 2 . Simulated parameters were
based on the reviewed experiences, considering high energy sav-
ings potential as reported by the researchers. Consequentially, dif-
ferent combinations of these parameters were considered in a
matrix, for the definition of the simulation scenarios, as shown
in Table 3 . Ten different scenarios were defined: an initial case
without the application of any passive cooling strategy (0 0 0 0), a
case which considered all strategies ( 1111) and all combinations
A. Prieto et al. / Energy & Buildings 175 (2018) 30–47 35
Tabl e 2
Simulated parameters for each passive cooling strategy.
Cooling
strategy
Simulated parameters
0 1
Shading NO Dynamic exterior shading (high reflectivity slats) on operation over 100 W/m
2
of solar irradiance on facades.
Glazing size (WWR) 100 % 25%
Glazing type Double clear glass Double reflective glass (6–13–6 mm with air in cavity)
Ventilation NO 5 ACH max when it’s thermodynamically feasible (external temperature below internal temperature)
Tabl e 3
Simulated scenarios based on the application of the evaluated strategies.
Simulated scenarios per climate Passive cooling strategies
Shading Glazing size (WWR) Glazing type Ventilation
No strategies applied 0 0 0 0
Only shading applied 1 0 0 0
Only WWR applied 0 1 0 0
Only glass type applied 0 0 1 0
Only ventilation applied 0 0 0 1
All strategies applied 1 1 1 1
No shading applied 0 1 1 1
No WWR applied 1 0 1 1
No glass type applied 1 1 0 1
No ventilation applied 1 1 1 0
Tabl e 4
Representative cities per climate group.
Climate group City CDD (26C)
Desert Riyadh 1583
Tropical Singapore 992
Temperate humid Hong-Kong 602
Temperate dry Athens 212
Temperate humid Trieste 88
Temperate dry Lisbon 69
resulting from the single application of each evaluated strategy
(10 0 0–0 0 01), and the application of all others with the exemp-
tion of the one to be evaluated ( 0111 –1110). This set of scenarios
allowed for the assessment of the isolated impact of each strat-
egy on a case without any other passive measure, and a case
where other measures were already in place. It is relevant to point
out that the application of all strategies is not necessarily pre-
sented as an optimal scenario, acting only as an example of the
application of several passive cooling strategies into a reference
building, without a process of conscious optimisation or integral
design.
The scenarios were simulated in representative cities from each
climate group. It was decided to consider two examples instead
of one in the case of temperate climates, to account for vari-
ations in climate severity within the group. Hence, six repre-
sentative cities were selected for the evaluation, as shown in
Table 4 along with their cooling degree days (CDD) considering
26 °C as base temperature. In summary, the total number of sim-
ulations was set at 60, comprising 10 scenarios in 6 representa-
tive cities, for a comprehensive evaluation and comparison of the
results.
3. Results and discussion
3.1. Definition of performance ranges for passive cooling strategies:
exploration of a database of research experiences
As explained before, the first part of the evaluation was based
on the statistical exploration of a database comprising performance
results obtained from several scientific articles. Table 5 shows ba-
sic statistical data to assess the energy savings potential of the
selected strategies, for two main climate groups: warm-dry and
warm-humid climates. A first issue worth mentioning is the fact
that reported energy savings reach higher values in the case of
warm-dry climates, evidenced by the large difference between
maximum reported values (from 22 to 37 percentage points de-
pending on the strategy), and the higher average and median val-
ues for all strategies, with the exemption of the use of shading
devices, which average similarly on both groups. This means that
the application of passive cooling strategies has more potential for
lowering cooling demands on warm-dry climates, instead of warm-
humid ones; which corresponds with the well-known complexity
and particular challenges associated with high humidity contexts
and tropical regions.
Furthermore, the reported energy savings in both climate
groups vary differently among the evaluated strategies. In the case
of warm-dry climates, the best average results are experienced
through the use of ventilation strategies (50%) and the reduction
of the window-to-wall ratio (34%); while in the case of warm-
humid climates, it is through ventilation and shading strategies,
with lower values of 33% and 28% respectively. The use of nat-
ural ventilation has been largely considered as a feasible cooling
strategy for dry climates, but its application in humid climates
presents more challenges due to specific humidity control require-
ments, which clearly affects its expected performance. On the con-
trary, the results from the use of shading devices present the low-
est variation between both climate groups, which seem to posi-
tion them as suitable alternatives with comparable effectiveness
regardless the context. These statements are based on the initial
assessment of general statistical data, so they will be expanded and
compared when discussing particular cases in detail in subsequent
sections.
Fig. 5 shows all reported energy savings data in a box-plot
graph to visualise the range of action of all evaluated passive cool-
ing strategies, in the two main defined climate groups: warm-dry
and warm-humid climates. On the one hand, it is possible to iden-
tify short ranges, which mean that there is consistency between
the gathered results for a particular strategy. This is the case of
window-to-wall ratio and glazing type reported energy savings for
warm-humid climates. On the other hand, long ranges mean more
dispersion among the results, such as the case of ventilation strate-
gies in both climate groups, and window-to-wall ratio in warm-
36 A. Prieto et al. / Energy & Buildings 175 (2018) 30–47
Tabl e 5
Statistical values to assess cooling demand savings per evaluated strategy.
Strategies Warm dry Warm humid
N Mean Median Minimum Maximum N Mean Median Minimum Maximum
Shading 84 26% 25% 4% 93% 57 28% 24% 5% 56%
Glazing size (WWR) 44 34% 34% 2% 76% 27 18 % 14 % −2% 44%
Glazing type 54 22% 15% 1% 70% 51 12% 10% 1% 40%
Ventilation 149 50% 52% 6% 91% 60 33% 30% 2% 69%
Fig. 5. Performance ranges considering all reviewed results per passive cooling strategy and main climate groups.
dry climates. Furthermore, a long performance range means that
the expected energy savings of a given strategy varies considerably
within the sample, thus, it depends on other factors and variables
to ensure a satisfying performance. Therefore, it is important to
detect and discuss boundary cases in order to isolate the charac-
teristics that make higher energy savings possible. The same goes
for the existence of outliers with markedly higher savings, identi-
fying and assessing their uniqueness within the larger sample, and
possibilities for replicability. In that sense, the fact that all strate-
gies considered minimum cooling savings from 0 to 5%, means that
the mere application of a passive strategy is not always enough to
ensure a satisfying performance, but it depends on several param-
eters that need to be carefully controlled to achieve the expected
results.
Each evaluated passive strategy is discussed separately, explor-
ing the gathered information to provide context to the results and
identify relevant parameters for performance optimisation. The dis-
cussion focuses on the best reported result, comprising variables
such as the climate severity of each evaluated context (variations
based on different climates within the climate groups), charac-
teristics of the intervention (internal parameters related to the
evaluated strategy), and characteristics of the base case (external
parameters related to the experimental setup and defined base
scenario).
3.1.1. Shading
The results obtained by the application of shading systems
show higher mean and median values, compared to cooling de-
mands savings from glazing type improvements. In general, shad-
ing reported values are consistent in both major climate groups,
averaging around 25% in potential cooling demand savings for
warm-dry and warm-humid contexts. Similarly, best reported re-
sults are comparable, reaching maximum values of 55.6% and
54.6% in the warm-humid climates of Bangkok (Aw) [44] and Tri-
este (Cfa) [58] ; and 53.8% and 45.2% in the hot-summer mediter-
ranean climate of Santiago, Chile (Csb) [61] and the hot desert
climate of Dubai (BWh) [37] , respectively. The 93.2% cooling sav-
ings reported by Baldinelli for a case in central Italy (Csa) [38] was
identified as an outlier considering its large difference and unique-
ness compared to the rest of the sample. Hence, it should be ex-
cluded from expected performance ranges from the application of
shading strategies.
Table 6 shows all shading related research experiences con-
sidered in the database, detailing their climate context, reported
range of cooling savings, information from the base case and
details of the intervention and evaluated parameters. Exploring
the differences from the evaluated cases, it could be seen that
in general, equator facing offices have larger cooling savings po-
tential, basically due to the high solar incidence in the north
and south façade in southern and northern hemispheres respec-
tively. Maximum reported values for equator facing offices are
55.6% [44] while maximum savings reach 39% in the case of
east-west oriented rooms in the humid subtropical climate of
Turin [64] .
Regarding evaluated shading types, it is possible to state that
the use of different shading systems does not categorically result
on markedly different cooling demand savings. Nonetheless, re-
ported results seem to hint at louvers and screens having more
A. Prieto et al. / Energy & Buildings 175 (2018) 30–47 37
Tabl e 6
Research experiences about shading, considering experimental setup, climate zones and reported cooling savings ranges.
Ref
Climate zones
(KOPPEN) Country Software Reference case details Evaluated parameters
Cooling
savings
[34] Hot summer
mediterranean (Csa)
Italy ESP-r Test office room with low-e double glazing, WWR of
32% and temperature comfort range between 20–26 °C
Evaluation of microperforated steel
screen, roller shade, and venetian
blinds, as shading devices between the
glass panes.
18% –24 %
[35] Hot desert (BWh) Kuwait EnergyPlus North-west facing
office with clear double glazing and
100 % WWR.
Overhang of 1 m width 8%–9%
[36] Humid subtropical (Cfa) Italy EnergyPlus South facing office room with Low-e double glazing
(Argon in the cavity) and 17% WWR. Temperature
comfort range between 20–26 °C.
External automated aluminium
venetian blind.
18%
[37] Hot desert
(BWh) UAE TRNSYS North facing office room with clear low-E double glass
as glazing unit with undisclosed window-to-wall ratio,
and temperature set-point defined at 23 °C.
External blinds with 0% transmission 45%
[38] Hot summer
mediterranean (Csa)
Italy CFD
simulation
South facing office room with clear double glazing and
100 %
WWR.
Movable aluminium horizontal slats
within the cavity of a double skin
façade prototype.
93%
[39] Hum Subtrop (Cfa)
Hot-summer mediterra
(Csa)
Italy EnergyPlus Complete typical office building with double glazing
and 30% WWR. Temperature comfort range between
20–26 °C.
Overhangs on south façade (1 m) and
fixed louvers on
east-west facades
26%–30%
[42] Hot summer
mediterranean (Csa)
Turkey EnergyPlus Complete office building with aspect ratio of 1:36,
clear single glazing and 40% WWR. Temperature
comfort ranges between 22–24 °C and 18–26 °C for
day and night time respectively. Infiltration of 0.2 ACH
Internal light color curtain (close
weaved).
4%–7%
[44] Tropical savanna (Aw) Thailand Visual Basic
6
South facing office room with variable depth. Heat
reflective single laminated glazing with 53% WWR and
temperature setpoint of 25 °C.
Horizontal slats in the cavity of a
double glazing unit.
37%–55%
[46] Humid subtropical (Cfa)
Hot-summer
mediterranean (Csa)
ITALY TRNSYS South facing room in five different office building
types, based on decade of construction and WWR.
Glazing type considers clear and tinted double glazing,
with 23%, 63% and 100% WWR according to each
building type. Temperature setpoint of 26 °C,
infiltration rate of 0.2 AC H
Light colored external venetian blinds,
with shading factor of 0.3. Shadings are
manually activated when direct solar
radiation exceeds 100 W/m
2
.
10% –27%
[49] Hot desert (BWh) UAE IES-VE Isolated office room with clear double glazing,
window-to-wall ratio of 60% and a temperature
set-point of 24 °C. South, west and east orientations
were considered in the analysis
Evaluation of fixed vertical (west-east)
or horizontal (south) lovers at 0
∗, and
dynamic louvers for all orientations
25%–38%
[53] Monsoon (Am) China EnergyPlus South facing room of a real building, with tinted-blue
single glazing and 72% WWR.
Evaluation of overhangs with different
width (1.2; 2.4; 3.6; 4.8)
7%–11%
[56] Tropical rainforest (Af) Malaysia IES-VE Complete high-rise office buildings with clear single
and low-e clear double glazing, and 100 % WWR.
Operative temperature set at 23 °C.
Evaluation of horizontal and vertical
louvres and egg-crate shading devices.
5%–10%
[58] Hum subtrop (Cfa)
Hot-summer mediterra
(Csa)
Italy ESP-r South facing office room of 20 m
2
, with low-e clear
double glazing and 45% WWR. Window with and
without reveal were used as base scenarios.
Flat panel positioned parallel to the
window, inclined by its horizontal axis
and widths of 1 and 2 m.
30%–56%
[61] Hot-summer
mediterranean (Csb)
Chile EDSL TAS Evaluation of an entire
office floor. Considering
different reference cases, based on the use of different
glazing types (clear single and double, and tinted
single and double glazing) and window-to-wall ratios
(20%, 50%, 100%)
The evaluation considered blinds at
west and east orientations, and the use
of either overhangs or blinds facing
north.
22%–54%
[63] Hot desert (BWh) Egypt EnergyPlus Evaluation of real office rooms in an Universit y
Campus, facing north, south and west orientations.
Clear single glazing and 50% WWR is considered.
Operative temperature is set to 23 °C.
Shading devices evaluated consider
horizontal louvres (0.5 m) and the use
of overhang of diverse width (0.5 m;
1 m; 1.5 m)
4%–20%
[64] Humid subtropical (Cfa)
Hot-summer mediterra
(Csa)
Italy Turkey EnergyPlus Evaluation of 18 office rooms in a referential building,
facing east and west orientations, with low-e double
glazing and 50% WWR. Temperature cooling setpoint is
25 °C during work hours and 30 °C during night time.
External venetian blinds with slat angle
of 45
∗, 50% reflectivity, slat separation
and width of 4 and 5 cm respectively.
Automated shading system depending
on solar intensity on façade
(250 W/m
2
).
36%–39%
[65] Hot desert (BWh) Egypt EnergyPlus Isolated office room with low-e clear double glass and
20% WWR. Evaluation was conducted for all four
orientations separately. Operative temperature set at
23 °C
Wooden solar screen (oakwood) of
2.7 ×1.8 m at 50 mm from the wall.
Perforation area:
90% Depth ratio:1.0
7%–30%
[67] Humid subtropical (Cfa) Italy EnergyPlus Single west facing office room of 28 m
2
, with low-e
double glass and 57% WWR. Temperature comfort
range between 20–26 °C.
External aluminium slats with different
angles, width and separation.
18%–29%
[68] Hot summer
mediterranean (Csa)
Greece EnergyPlus South and east facing office rooms within a reference
building defined in ISO15265 and ISO13790. Operative
temperature setpoint is 24.5 °C and infiltration rate is
0.5 ACH. WWR and Glazing types varies (WWR from
10– 100% and 9 glazing units are tested).
Movable shading device, activated
when incident solar radiation on
vertical plane exceeds 300 W/m
2
.
Evaluation of shading factors of 25%,
50% and 75%
9%–45%
[73] Humid subtropical
(Cwa)
South
Korea
EnergyPlus South facing office room of 100 % WWR and various
glazing types (clear single, double and triple, and low-e
double and triple glazing). Temperature comfort range
between 22–26 °C.
External slats (25 mm slat separation,
width and distance to glass).
Reflectance of 0.1
9%–14%
38 A. Prieto et al. / Energy & Buildings 175 (2018) 30–47
Tabl e 7
Research experiences about glazing size (wwr), considering experimental setup, climate zones and reported cooling savings ranges.
Ref
Climate zones
(KOPPEN) Country Software Reference case details Evaluated parameters
Cooling
savings
[38] Hot summer
mediterranean (Csa)
Italy CFD
simulation
South facing office room with clear double glazing and
100 % WWR.
50% WWR 49%
[39] Hot-summer mediterr
(Csa) Hum subtrop
(Cfa)
Italy EnergyPlus Complete typical office building with double glazing and
60% WWR. Temperature comfort range between 20–26 °C.
30% WWR 34%–36%
[48] Hot-summer
mediterranean (Csa)
Italy Greece EnergyPlus Complete office building with low-e clear triple glazing,
80% WWR and externa l automated venetian shading.
Separated evaluations per orientation are considered.
Temperature comfort range is set between 20–24 °C
Several WWR values were
evaluated from 20% to 37%
(optimised values per
orientation)
11% –17%
[53] Monsoon (Am) China EnergyPlus South facing room of a real building, with tinted-blue
single glazing and 60% WWR.
36% and 48% WWR.
Additionally, the use of
2.4 m overhang was
evaluated for both cases.
6%–12%
[57] Trop rainforest (Af)
Hum subtrop (Cfa)
The
Philippines
China
EnergyPlus
COMFEN
Complete building consisting of 4 perimeter zones with 5
office rooms each. Clear double glazing on windows with
100 % WWR.
Several WWR values (25%,
50%, 75%)
5%–44%
[59] Tropical savanna (Aw) Thailand Numerical
calculations
South facing office room with several glazing types (heat
reflective, tinted and low-e laminated glazing) and either
40% or
68% WWR. Six external slats per glass pane are
used as shading device.
WWR values of 40% and
20% were evaluated
−2%–24%
[61] Hot-summer
mediterranean (Csb)
Chile EDSL TAS Evaluation of an entire office floor. Considering different
reference cases, based on the use of different glazing types
(clear single and
double, and tinted single and double
glazing) and 100 % WWR. Variations considered no shading
device and the use of overhang or louvres in north, east
and west orientations.
WWR values of 50% and
20% were evaluated
21%– 76%
[63] Hot desert (BWh) Egypt EnergyPlus Evaluation of real office rooms in an Universit y Campus,
facing north, south and west orientations. Clear single
glazing and 50% WWR is considered. Operative
temperature is set to 23 °C.
Several WWR values (40%,
30%, 20%)
2%–12%
[64] Hot-summer
mediterranean (Csa)
Humid subtropical (Cfa)
Italy
Turkey
EnergyPlus Evaluation of 18 office rooms in a referential building,
facing east and west orientations, with low-e double
glazing and 50% WWR. External venetian blinds are used
as shading device. Temperature cooling setpoint is 25 °C
during work hours and 30 °C during night time.
25% WWR 19%–20%
savings potential than the use of overhangs, which make sense
considering the amount of exposed window area. Maximum re-
ported cooling savings are 55.6%, 53.8% and 41.1% for the use of
screens [44] , external louvres [61] , and overhangs [61] , respec-
tively. In any case, further information would be needed for a
detailed evaluation of several shading types in different climate
zones, besides considering particularities from each case and shad-
ing design. It is the authors’ opinion, that especially in the case
of shading strategies, referential information is useful and relevant
for early design stages but it should always be contrasted with a
detailed analysis of the actual devices being used, due to design
particularities and dynamic shading patterns of a specific location
and orientation.
3.1.2. Glazing size (WWR)
The results of glazing size evaluations show a considerable dif-
ference between warm-dry and warm-humid climate groups. In
the first group, average cooling demand savings are 34%, while in
the second they only reach 18%. The fact that median values are
lower than the average in the latter (14%), mean that expected
average cooling savings for warm-humid climates could be
assumed to be lower (around 14% −18%), based on the analysed
sample. In terms of maximum reported values, the difference
grows apart, evidenced by the 76.4% savings obtained for the
warm-dry climate of Santiago, Chile (Csb) [61] and the 43.7% and
41.1% registered by Lee et al. for warm-humid cases in Shanghai
(Cfa) and Manila (Af), respectively [57] . It is relevant to point