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Simulation Method to Assess Thermal Comfort in Historical Buildings with High-Volume Interior Spaces—The Case of the Gothic Basilica of Sta. Maria Del Mar in Barcelona


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Concerns about the energy performance of heritage buildings have grown exponentially over the last decade. However, actions have been limited to reducing energy consumption and carbon emissions. Another perspective must be studied—the thermal comfort of users, for human welfare and health. The assessment of thermal comfort inside a historic building with a single, large volume interior space is not easy. The complexity increases if the building has high cultural protection and its envelope cannot be altered, to preserve its historical values. This paper focuses on this kind of building and describes a dynamic simulation method used to assess thermal comfort in the Gothic Basilica of Sta. Maria del Mar in Barcelona. The basilica’s interior thermal conditions are intense cold during the winter and extreme heat and sultriness during the summer. Several simulation scenarios were considered to highlight the failure to obtain thermal comfort for users through passive strategies during the summer period. When all the factors are considered, the only valid strategy is to introduce an active system. This must be minimized according to three criteria: reducing operational periods, considering just the air volume next to users and adjusting the level of comfort requirement.
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Sustainability 2021, 13, 2980.
Simulation Method to Assess Thermal Comfort in Historical
Buildings with High-Volume Interior Spaces—The Case
of the Gothic Basilica of Sta. Maria Del Mar in Barcelona
Belén Onecha
* and Alicia Dotor
Architecture Technology Department, Barcelona School of Architecture, Polytechnic University
of Catalonia, 08028 Barcelona, Spain
Independent Researcher and Architect, Association of Architects of Catalonia, 08005 Barcelona, Spain;
* Correspondence:; Tel.: +34-647-548-558
Abstract: Concerns about the energy performance of heritage buildings have grown exponentially
over the last decade. However, actions have been limited to reducing energy consumption and car-
bon emissions. Another perspective must be studied—the thermal comfort of users, for human wel-
fare and health. The assessment of thermal comfort inside a historic building with a single, large
volume interior space is not easy. The complexity increases if the building has high cultural protec-
tion and its envelope cannot be altered, to preserve its historical values. This paper focuses on this
kind of building and describes a dynamic simulation method used to assess thermal comfort in the
Gothic Basilica of Sta. Maria del Mar in Barcelona. The basilica’s interior thermal conditions are
intense cold during the winter and extreme heat and sultriness during the summer. Several simu-
lation scenarios were considered to highlight the failure to obtain thermal comfort for users through
passive strategies during the summer period. When all the factors are considered, the only valid
strategy is to introduce an active system. This must be minimized according to three criteria: reduc-
ing operational periods, considering just the air volume next to users and adjusting the level of
comfort requirement.
Keywords: thermal comfort in historical buildings; dynamic simulation method for the assessment
of historical buildings; historical buildings with large volume interior space; heritage intervention
1. Introduction
It is difficult to establish the energy behavior of historical buildings, and even harder
if we want to relate this behavior to the welfare of users. Consequently, an assessment
method is required that considers the specific characteristics of historical buildings with-
out insulation, and users’ sensations depending on their activity, clothes and even their
comprehension and perception of the historical building.
In mild and continental climates, the feeling of lack of thermal comfort inside histor-
ical buildings used to be very high during winter and very low or nonexistent during
summer, due to the wall thickness and the small surface area of windows. However, the
case chosen to illustrate the proposed method, the Basilica of Santa Maria del Mar in Bar-
celona, does not provide thermal comfort during winter or summer. In fact, discomfort is
particularly high during the summer. The issue is important, as climate change experts
recommend considering scenarios with a 70-year horizon [1] in which the winter season
will be increasingly mild while the summer season will be ever warmer. The change in
the summer season will cause overheating and an increase of energy loads and carbon
emissions [2]. This phenomenon is intensified within historic city centers, where the com-
Citation: Onecha, B.; Dotor, A.
Simulation Method to Assess
Thermal Comfort in Historical
Buildings with High-Volume
Interior Spaces—The Case of the
Gothic Basilica of Sta. Maria Del Mar
in Barcelona. Sustainability 2021, 13,
Academic Editor: Ali Bahadori-
Received: 2 February 2021
Accepted: 2 March 2021
Published: 9 March 2021
Publisher’s Note: MDPI stays neu-
tral with regard to jurisdictional
claims in published maps and insti-
tutional affiliations.
Copyright: © 2021 by the authors. Li-
censee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and con-
ditions of the Creative Commons At-
tribution (CC BY) license (http://crea-
Sustainability 2021, 13, 2980 2 of 20
bination of pollution, modification of atmosphere conditions and covering of the soil sur-
face produces urban heat islands (UHI) [3]. This is a serious problem for Mediterranean
countries where high consumption peaks already exist due to cooling systems during
summer months [4,5] and cooling requirement makes it impossible to achieve a near-zero
energy building without energy recovery [6]. For heritage buildings, climate change is a
great challenge, since the risk of inside overheating and the damage caused by increased
relative humidity (RH) affects not only the building or the thermal comfort of users, but
also the preservation of artworks that are usually kept inside the buildings [7].
Martínez Molina et al. highlighted the importance of reaching thermal comfort in
public use buildings [8]. In fact, this is one of the main objectives when buildings are ret-
rofitted, especially if they are historical buildings. What is more, “the assessment of ther-
mal comfort inside buildings occupies a flourishing line of research due, to some extent,
to the scarce available verified data” (Translation by author from the Spanish original.) [9]
(p. 1817–1818). The difficulty of this kind of “thermal” intervention has been explored by
several researchers. All of them agree that it is a very challenging subject because these
buildings are key to improving the local economy in tourist centers [10]. However, there
are many intervention constraints due to regulations on the preservation of the buildings’
values and the fact that historical properties are often excluded from compliance with
regulatory requirements, as legislation recognizes that historic values are the priority [11–
Historical buildings have no thermal insulation on their envelope, but considerable
thermal inertia derived from the thickness of their masonry walls, which have a high ca-
pacity for heat storage. In general, when we consider the summer period, the inertia of
the envelope walls maintains the levels of temperature (T) and Relative Humidity (RH),
while during the winter this effect cannot provide thermal comfort. However, there is no
simple method for establishing the thermal transmittance of the envelope that considers
solar absorption, wind direction and speed [14–16].
The most common passive solution that has been studied is adding thermal insula-
tion to the building envelope [5,17,18]. However, in historic buildings, it is not always
feasible to insulate the envelope, since the preservation of their architectural characteris-
tics does not allow such modifications. In addition, some authors have verified that retro-
fit interventions by insulation could reduce the drying capacity of walls and modify the
temperature gradient. This could undermine the conservation of historic envelopes [19].
Another passive strategy can be implemented—natural ventilation as a much more
effective method for reducing cooling than reducing the thermal transmittance of the en-
velope [20]. It has been demonstrated that the overheating risk that can occur in this kind
of buildings, may be reduced with night ventilation [21,22]. Other authors investigated
the case of a historical building in Catania, in which they combined a high thermal inertia
mass with natural ventilation to prevent overheating and provide good comfort levels.
This reduced the need for cooling systems during the summer. However, the same au-
thors highlighted several setbacks that can arise in night ventilation strategies, for exam-
ple when the thermal oscillation between day and night is lower than 10 °C. In addition,
even though this is the most economical solution for the natural cooling of buildings, it is
very difficult to control since the directionality and intensity of air flows change with the
climate [23–25]. Balocco et al. explained that annual variation in hygrothermal parameters
inside and outside of historical buildings are characterized by slow differences that can
produce minor changes, in contrast to impulsive seasonal variations that are much faster,
for instance the effects of intense artificial lighting or even heating, ventilation and air
conditioning, both without control [26,27].
The characteristics of the interior space of the Santa Maria del Mar building are great
height and a large inside air volume. Few authors deal with such an important factor.
Muñoz-González et al. refer to several studies on thermal comfort in religious buildings
that have this type of nave space. They note that most of them are in continental climates,
with harsh winter periods. Accordingly, facilities that may be introduced, such as radiant
Sustainability 2021, 13, 2980 3 of 20
floor heating, thermal benches or electric carpets, are designed to heat the buildings dur-
ing winter, rather than to counter the effects of the extreme heat and sultriness that are
typical of Mediterranean cities in the summer. The same author states that the implemen-
tation of only passive systems in these buildings does not completely eliminate the risk of
thermal discomfort, and mechanical and biological degradation. A combination of active
and passive strategies improves all these aspects when it functions 24 h a day but has the
disadvantage of very high energy consumption. In some cases, only active strategies can
be used, to preserve the cultural values of the building envelope. If their use is reduced to
12 h a day, energy savings can reach 38%. When their use is limited to the short time of
celebrating mass, savings reach 90%. However, if we consider the preservation of art-
works, air systems with relative humidity (RH) control are preferred for 24 h periods, to
maintain the stability of environmental conditions [28,29].
To establish the user’s comfort, the system’s performance and its energy consump-
tion, the information should be processed through a simulation software tool that can
model the historic building characteristics and its behavior to raise several performance
hypotheses [30]. A steady state or dynamic state calculation can be used. Dynamic state
calculations consider short time intervals to distinguish heat and ventilation flows during
use of the building. The last years some interesting publications about dynamic simula-
tions on existing buildings have been carried out. Amirkhani et al. used the simulation
software TAS (Thermal Analysis Software) version 9.4.4 in order to assess different strat-
egies to improve their energy efficiency. Some strategies were based upon improving the
energy performance of the own building elements, for instance, adding insulation on the
inside face of the envelope or changing the windows incorporating low-e windows films.
[31,32]. Other strategies consisted on modifying the active systems of the buildings, for
example using splits with a high Energy Efficiency Ratio cogeneration or trigeneration
[33–35]. Alwetaishi used the same software after gathering qualitative data and monitor-
ing onsite [36]. Other thermal behavior simulation software has been used, with the aim
of reducing energy consumption. Examples are DOE-2 program, a software developed by
University of California and Hirsch, that can predict the energy use for all types of build-
ings [37]; the ThermoSem model, which is a thermophysiological model to predict thermal
sensation in the built environment to obtain a more individualized assessment [38] and
the well-known Design builder.
This last is frequently used to develop dynamic simulations to analyze thermal com-
fort in historical buildings. Muñoz-González et al. performed a dynamic simulation to
analyze the heat transfer processes, the air-conditioning systems and other factors related
to energy consumption in a church in southern Spain. They concluded that, during the
summer, the church achieved thermal comfort 95% of the time and the need for air condi-
tioning was reduced to winter heating. They noted the huge energy consumption of win-
ter heating, due to the large inside air volume and the thermal inertia of the envelope
walls [28].
Other authors, such as Gagliano et al., simulated the thermal performance of a tradi-
tional massive building in a Mediterranean city. They found that the building envelope
maintained inside temperature except for minor oscillations. The need for air-condition-
ing was largely avoided, and night ventilation even accounted for 30% of cooling [16].
Cornaro et al. have been working on a method based on in situ monitoring and dy-
namic simulation to assess the most suitable solutions for rehabilitation of buildings that
have great historical and artistic value. Their research differed from the case study in this
paper, as they examined a multi-story building, with multiple rooms of usual height and
volume, whose main problem was the need for heating during the winter period [39].
D’Agostino and Congedo analyzed the crypt of Lecce Cathedral through 20 CFD
(Computational Fluid Dynamics) 3D models and 5 ventilation scenarios to find a solution
that could generate an optimal interior microclimate for the preservation of the building.
The scenarios were simulated by combining diverse hygrothermal exterior conditions and
Sustainability 2021, 13, 2980 4 of 20
several entrances for ventilation air flows, which resulted in several air layers, depending
on density, moving at different temperatures under the force of gravity [40].
Litti 2015 focused on microclimate comfort people (MCP) and included parameters
that could affect artwork, like RH [41].
Muñoz et al. simulated a few Baroque churches in southern Europe from the per-
spective of the climate change foreseen for 2050. They carried out monitoring campaigns
to validate the dynamic simulation. The churches showed a rising demand for cooling and
a fall in demand for heating. The researchers identified an increase in use of active sys-
tems, which functioned for periods of at least 12 h to assure human comfort and artwork
preservation [7].
Most of the above authors considered that the main thermal discomfort problem in-
side historical buildings with thick inertial walls occurs during the winter. During the
summer, thermal comfort is acceptable even without cooling, if it is possible to protect
against solar gains and heating loads and natural ventilation is controlled, especially at
night [42]. However, there are very few studies on the main thermal discomfort problem
in Mediterranean climates, during summer season, inside historical buildings, and partic-
ularly those characterized by high relative humidity. Additionally, there is a lack of sci-
entific literature about thermal comfort in historical buildings with interior spaces of great
height, huge air volumes and a considerable level of cultural protection. It must not be
forgotten that this protection prevents interventions on the building envelope that could
alter the historical value.
Considering the above, the hypotheses that will be discussed in this paper are the
For historic buildings in Mediterranean climates, which are characterized by high
RH, the thermal discomfort level during the summer period is not negligible. It reaches
levels that can be much higher than winter thermal discomfort levels.
In these cases, when the envelope cannot be altered because of cultural protection of
the building, the only feasible passive strategy to improve thermal comfort is natural ven-
tilation. However, when temperature and RH conditions are very similar inside and out-
side the building, neither natural ventilation nor just mechanical ventilation are effective.
Several criteria must be considered to minimize the impact on the historic building
of the facilities that are required to achieve thermal comfort: operating periods, air volume
and the required level of thermal comfort.
This paper considers all these aspects and proposes a methodology based on three
steps: strict characterization of the building and the climate, onsite monitoring, and dy-
namic simulation. All of these steps are followed to analyze users’ thermal comfort inside
historical buildings of great height and volume located in humid Mediterranean climates,
particularly during the summer period when the hygrothermal conditions are harsh and
will become even harsher if the long-term forecasts come true. The main aim is to establish
several strategies to achieve thermal comfort at a less demanding level than that required
in modern buildings, that are used for long periods, and considering that any intervention
cannot affect the building envelope, to preserve its cultural values.
2. Materials and Methods
2.1. Case Study
The Basilica of Santa Maria del Mar is a Gothic temple built between 1329 and 1383
in the Ribera neighborhood. It was given the name “del Mar” (of the sea) due to its prox-
imity to the sea. The Basilica has great historical, sentimental and identity value for the
people of Barcelona. It competes with its simplicity and beauty with the nearby Barcelona
Cathedral, built between 1298 and 1417.
The master builders of Santa Maria were first Berenguer de Montagut and then Ra-
mon Despuig. The building is in the style of Mediterranean Gothic and follows the model
of a “hall” church. In hall churches, the naves are of almost the same height and are just
Sustainability 2021, 13, 2980 5 of 20
separated by slim columns, which contributes to the visual perception of a unitary space.
This is in contrast to French Gothic, in which the central nave is always higher than the
lateral naves. This is one of the main singularities of this church, together with its quick
construction. It had a direct impact on the thermal and lightning conditions, since the
main windows are on the façades of the lateral naves and have restricted dimensions to
avoid excessive solar gains, as can be seen Figure 1. This is another difference with French
Gothic churches, where the main windows are on the main nave façades and have large
surfaces to improve natural lighting conditions.
The exhibited artworks are mostly made of stone as the fire of 1936 burnt most of
those that were made of wood.
Santa Maria del Mar was declared a heritage building with national cultural protec-
tion in 1931.
Figure 1. Interior view of Santa María del Mar Basilica. Source: (access on 17 December
2.2. Method for Assessing Thermal Comfort Conditions
The method to assess users’ thermal comfort inside historical buildings with large
volume spaces was developed following these steps. In the first phase, data are collected
on the building, the climate and environment, and the users’ activity and clothing. In a
second stage, onsite monitoring of hygrothermal data takes place. In the final phase, a
dynamic simulation with Design Builder software, with the powerful calculation engine
Energyplus, is carried out for different scenarios of use and ventilation.
These steps are described in detail in the following sections and developed for the
case study of Santa Maria del Mar in Barcelona.
2.2.1. Data Collection on the Building and Users
The Basilica is located in the Ribera neighborhood, also called the Born, and is char-
acterized by high building density, narrow streets and buildings five or six stories high,
as can be observed in Figure 2. All these factors contribute to the urban heat island effect.
The basilica is oriented in the usual direction, the apse looking to the east and the
main entrance on the west façade, the east façade is partially adjacent to another building.
Sustainability 2021, 13, 2980 6 of 20
Figure 2. Aerial view of the basilica in the historical Ribera neighborhood.
In research on thermal comfort inside a building, it is essential to obtain deep
knowledge of its construction. Santa Maria del Mar is 33 m wide, 33 m high and 80 m
deep. It was built of Montjuïc stone shaped into small ashlars for the façade walls that are
80 cm thick, and small blocks for the ribbed vaults that are 40 cm thick. All these stone
elements are bare, without any kind of coating.
The main nave is covered by a flat roof. A gap was left between the vault and the
roof, which is full of empty clay vases to make an air chamber and consequently reduce
the horizontal thrust of the main nave vaults. The lateral naves are covered by a flat roof
over solid vaults, to increase their horizontal thrust and compensate for those of the cen-
tral nave. Every vault has openings connected to the roofs, which formed the historical
ventilation system. These orifices are usually open and must be closed before rainy days.
The façades are characterized by a greater proportion of massive walls than open-
ings, as can be seen on the plans of the building in Figure 3. Windows are Gothic roses for
the central nave and rectangular shapes topped with a pointed arch for lateral naves and
chapels. Only a small part of the windows can open, adding up to a total of 7.20 m
ventilation surface. The four doors made of wood are the four entrances to the temple and
comprise a total of 16.50 m
of ventilation surface.
The floor of the basilica is comprised of stone paving without any kind of insulation
Sustainability 2021, 13, 2980 7 of 20
Figure 3. Building plans: longitudinal section and cross-section.
Another key factor in user thermal comfort is occupancy according to the time of day.
The parish of Santa Maria del Mar provided data on worship use and exceptional use,
referring the maximums and minimums, as summarized in the following table.
In parallel to worship occupancy and during the remaining opening times of the tem-
ple, cultural visits take place. The flow of visitors is variable and difficult to specify but is
much greater during the summer, when there are more tourists in Barcelona.
To assess thermal comfort, the user’s activity and the degree of physical movement
that it implies must be specified. In this case, light activity was considered that involves
standing up, a relaxed cultural visit in which visitors walk slowly through the temple, and
Sustainability 2021, 13, 2980 8 of 20
church masses. This movement intensity is correlated with a metabolic rate of 93 W/m
(ISO 7730:2006/Appendix A/Table 1).
Finally, clothing must be defined, which depends on climate. For the summer, 0.5 clo
was considered (light clothing). For the winter, 1.5 clo was defined, which implies a thick
jacket. For the rest of the year, the values have been interpolated.
Table 1. Opening hours and occupancy data.
Opening hours Monday to Friday 9 a.m. to 8.30 p.m.
Saturday and Sunday 10 8.30 p.m.
Occupancy data
Exceptional (concerts or celebrations) 2000 people
Daily mass (7.30 p.m.) <200 people
Saturday mass (7.30 p.m.) 200 people
Sunday mass (12 p.m. and 7.30 p.m.) 700 people
Cultural visit Variable, larger number in the summer
2.2.2. Onsite Monitoring
On three occasions during the summer of 2020, monitoring was carried out inside
and outside the basilica to measure the hygrothermal air parameters. A data logger RS-
PRO 1.160 was used to obtain the dry-bulb temperature and the relative humidity of air.
Figure 4 shows where several measurements were made inside and outside the temple,
some in the central corridor and the others at the four main entrances, which are both
indoors and outdoors. Table 2 outlines the monitoring data.
Figure 4. Position of monitoring points on the basilica plan.
Table 2. Onsite Temperature and relative humidity (RH) monitoring, corresponding PMV (Pre-
dicted Mean Vote) and PPD (Predicted Percent of Dissatisfied people).
Monitoring 1
Monitoring 2
Monitoring 3
5.30 p.m.
9.30 a.m.
5.30 p.m.
6–8 people
6–8 people
15–20 people
Passive systems
4 doors opened
4 doors opened
4 doors opened
Active systems
4 small fans
29–31 °C
28–29 °C
30–31 °C
Sustainability 2021, 13, 2980 9 of 20
These data have been compared with data from a nearby weather station—those ob-
tained the same day of the year in the previous five years and those obtained during the
rest of the days of the same month and year. The statistics for the results are shown below
on Tables 3 and 4.
Table 3. T and RH for 7 July in the last five years. Average compared to the rest of days.
Date Tm
Tmax Abso-
lute Month
Tmin Abso-
lute Month
plitude Aver-
age Month
07.27.20 27.9 31.9 24.5 64 26 29 23.6 3 64.61
07.27.19 24.1 26.5 18.3 77 26.4 33.5 18.3 6.1 66
07.27.18 27.8 31.6 24.7 59 26.5 33.5 20.2 6.1 64
07.27.17 26 29.8 22.3 67 25.4 28.5 22.9 5.5 67
07.27.16 26.4 29.1 24.3 66 25.7 32.2 19.6 5.8 62
For Monitoring 1 (27 July 2020), compared to the rest of the days of the same month,
there were 35% of days with a higher minimum temperature, 3% of days with higher
maximum temperature and 55% of days with a higher RH. Clearly, this was a hot day for
the month. It was not so wet and was not far from the conditions in the previous five years
on the same day. It must be underlined that thermal amplitude between night and day
had a very low value.
Table 4. T and RH on 12 August in the last five years. Average for the rest of the days.
Date Tm
Tmax Abso-
lute Month
Tmin Abso-
lute Month
Thermal Am-
plitude Aver-
age Month
For Monitoring 2 and 3 (12 August 2020), compared to the rest of the days of the same
month, there were 3% of days with a higher minimum temperature, 25.5% of days with a
higher maximum temperature and 58% of days with a higher RH. It was a warmer day
than the same day in the previous five years, and less wet. Again, the thermal amplitude
between night and day had a low value.
If we turn to the indoors monitoring on Table 2, several parameters on it should be
highlighted because of their importance in the justification of this research. First, occu-
pancy was unusually low compared with regular occupancy for the summer period. This
was a direct consequence of the Covid-19 health crisis and the lack of cultural visitors.
Secondly, the perception of sultriness should be highlighted. This depends mostly on the
T and HR as shown in Figure 5, which we usually call the Heat index. The index represents
what the temperature feels like to the human body when RH is combined with the air
temperature. When atmospheric moisture content is high, the rate of evaporation from
the body to regulate its temperature decreases, so it feels warmer.
Sustainability 2021, 13, 2980 10 of 20
Figure 5. Heat Index chart and corresponding health impacts. Source: National Weather Service
(, accessed on 31 December 2020).
The data from Table 2 were transferred to the table in Figure 5. It can be seen that for
Monitoring 1, with a maximum temperature of 31 °C and 64% RH, thermal perception is
36 °C; for Monitoring 2, with 29 °C and 70% RH, the perception is 33 °C; and for Monitor-
ing 3, with 31 °C and 60% RH, the perception is 35 °C. All these data are located on the
“Extreme caution” area of the table. Surprisingly, the sultriness perception was higher for
Monitoring 2, with the lowest heat index. As a hypothesis, this could be attributed to the
high RH registered in contrast to outside RH and the T early in the morning.
This information should be reviewed considering the usual occupancy data, which
uses to be much higher than that of 2020. Theoretically, more visitors during the summer
period would mean a latent heat increase, which would result in higher RH. If this is above
80%, with the same T that was monitored, the thermal perception could be above 40 °C.
This corresponds to the “Danger” area of the table.
2.2.3. Dynamic Simulation
The dynamic simulation software used was Design Builder, which runs with the cal-
culation motor engine Energyplus v8.9. Data were introduced progressively in following
order—first the building configuration, then the occupancy, activity and clothing of users,
followed by the climate data, and finally the simulation scenarios. Each one of these
phases are described below in detail.
The first step consisted of modelling the building, specifying the interior air volume
and the surfaces of the envelope elements that are responsible for the thermal exchange,
as well as the materials and their theoretical thermal performance, as shown in Figure 6
and Table 5.
Sustainability 2021, 13, 2980 11 of 20
Figure 6. Overall view of the building with elements of the environment and shadows and a view
of thermal surfaces of the envelope colored by typology.
Table 5. Parameters of the envelope elements.
Envelope Elements
Theoretical Thermal Transmittance,
U (W/m
Enclosure Thick-
ness (cm)
Solar Heat Gain Co-
Stone wall 1.20 80
Roof with air chamber 1.17 130
Solid roof 1.62 60
Pavement 0.25 33.5
Door 2.67 3.5
Massive element 3.02 90
Window (low ratio
opaque/transparent) 6.78 0.32
Window (high ratio
opaque/transparent) 5.78 0.22
Then, the occupancy data, user’s activity and clothing were introduced. Specifically,
the air volume in the users’ space was studied, in around the first 3 m above the floor,
with an expected occupation of 384 people. This number was determined by the simula-
tion software for a public use building, like a museum, considering 0.15 people/m
. This
last item of data gives an approximation of the occupancy during the summer period,
with a great influx of visitors. These parameters are detailed in Table 6.
Table 6. Area, volume, occupancy and clothing.
Public area ground floor, m
Total air volume, m
Visitors’ air volume, m
Lower area air volume, m
Intermediate area air volume, m
Higher area air volume, m
Lightning internal loads ground floor, W/m
Simulation occupancy 384
Clothing insulation (clo) Range of values interpolated month after month, from 0.5 for
the summer to 1.5 for the winter
Afterwards, climate data were introduced and were calibrated according to two fac-
tors—climate data (T, RH) provided by a near weather station, which should reflect the
urban heat island effect characteristic of dense historical urban centers, and data corre-
sponding to onsite monitoring outside the temple.
Sustainability 2021, 13, 2980 12 of 20
Lastly, simulation scenarios need to be defined to establish the degree of user thermal
comfort, particularly during the summer, and to identify corrective strategies that should
affect only the air volume around the user up to a maximum of 3 m height and not affect
the building envelope, to preserve its cultural values.
The proposed scenarios should depart from the most similar situation to reality.
Strategies must be added gradually according to two criteria—the energy consumption
and the impact on the monument. The first scenario (A) is the point of departure, the cur-
rent state with no ventilation at all, which implies no energy consumption and no impact.
The second scenario (B) considers the only passive strategy that can be implemented with-
out altering the envelope of the building, which is natural ventilation through opening
windows and doors. The third scenario (C) proposes mechanical ventilation and several
sub-scenarios depending on the ventilation flow rate. This is the beginning of energy con-
sumption and impact. The fourth and last scenario (D) considers mechanical ventilation
with cooling, also with several sub-scenarios, that leads to more consumption but proba-
bly the same impact as the previous scenario.
At this point, the concept of thermal comfort should be defined. For this research, the
criteria of the Fanger method were applied, which consider thermal comfort depending
on two indices: the predicted mean vote (PMV) and predicted percentage dissatisfied
(PPD). These show respectively the medium thermal sensation inside a building, and the
percentage of people who will feel uncomfortable. A PPD < 6% was considered equivalent
to a PMV near 0 and very strict thermal comfort; PPD < 10% is related to PMV from −0.5
to +0.5 and ideal thermal comfort; PPD < 20% corresponds to PMV from −1 to +1 and ac-
ceptable thermal comfort. The latter was chosen as suitable for this case study, as it was
considered an adequate comfort level for short occupancies, like a cultural visit or church
mass. In addition, it was considered that users understand that is not possible to be as
demanding with thermal comfort inside a historical building of cultural value as inside a
new building.
3. Results
Below are the results for the four scenarios.
3.1. Scenario A: Current State
In the absence of any natural or mechanical ventilation, the degree of thermal dis-
comfort during the summer months widely exceeded the value PMV +1, and even reached
the value of PMV+2 in August, which was unacceptable according to the code ISO
7730:2006. In the graphics of Figure 7, the red line shows the limits for PMV+1.
Figure 7. PMV value throughout the year with no ventilation.
Sustainability 2021, 13, 2980 13 of 20
3.2. Scenario B: Natural Ventilation (NV)
This scenario considered the air flow rate through the doors and windows during the
opening hours of the basilica, from 9 a.m. to 8.30 p.m. Night ventilation is not an option,
as there is no night-time surveillance, and the opening of doors and windows may cause
unwanted intrusion.
As can be seen in Figure 8, scenario B barely changed from scenario A and a very
similar number of thermal comfort hours was obtained.
Figure 8. Comparison between scenarios A (blue) and B (orange) for the entire year and detailed
for 3 days in July.
These data can be interpreted when we consider the onsite monitoring of T and RH
inside and outside of the basilica. It can be seen that any variations in these parameters
indoors/outdoors were almost imperceptible, so efficient natural ventilation was not ob-
3.3. Scenarios C: Mechanical Ventilation (MV)
This case simulated and analyzed the effectiveness of a mechanical ventilation sys-
tem to renovate the air volume of the temple, strictly in the area from the floor up to 3 m
height. The total air volume of the church, which is 33 m high, was not considered, as only
the three lower meters are occupied.
To establish the ventilation air flow rate, the requirements of the Spanish law on heat-
ing, ventilation and air conditioning systems (RITE) were taken into account. For church
mass occupancy or cultural visits, air quality IDA2 would be sufficient, but for exceptional
concerts and celebrations air quality IDA3 would be required. Figure 9 shows the required
ventilation air flow rates to guarantee good quality of interior air.
Sustainability 2021, 13, 2980 14 of 20
Figure 9. Air flow rates by occupancy.
Several sub-scenarios were considered depending on the operating hours of the ma-
chines. Scenario C.1 considered mechanical ventilation between 9 a.m. and 8.30 p.m. Sce-
nario C.2 contemplated mechanical ventilation between 5 a.m. and 8.30 p.m. For both
cases, the simulation took different air flow rates, to identify different degrees of thermal
comfort, and the electrical power that would be necessary: 2500 l/s (a), 8750 l/s (b) and
10,000 l/s (c).
For the first timing, scenarios C.1.a (2500 l/s), C.1.b (8750 l/s) and C.1.c (10,000 l/s), the
percentage of acceptable thermal comfort hours was 69%, which means 750 h with PMV
> +1 or discomfort hours. Figure 10 shows the comparison between the original scenario,
A, and the scenarios C.1.a, C.1.b and C.1.b for the month of September.
Figure 10. Comparison between scenarios A, C.1.a (2500 l/s), C.1.b (8750 l/s) and C.1.c (10,000 l/s)
for the month of September and machines operating between 9 a.m. and 8.30 p.m.
For the second option of machine operating hours between 5 a.m. and 20.30 p.m., and
the same air flow rates reflected in scenarios C.2.a, C.2.b and C.2.c, 700 h of thermal dis-
comfort still remained. Therefore, it could be concluded that even when it operates most
of the day, mechanical ventilation is not enough to overcome thermal discomfort.
3.4. Scenarios D: Mechanical Ventilation with Cooling (MVR)
Once the thermal dissatisfaction described in the previous sections had been verified,
it was considered necessary to go one step further and simulate the effectiveness of a me-
chanical ventilation system with the capacity to add active cooling. As in scenario C, the
area of renovated air was limited to the lower 3 m. There are also two operating schedules,
from 9 a.m. to 8.30 p.m. for scenario D.1, and from 5 a.m. to 8.30 p.m. for scenario D.2.
Three options for renovating air flow were evaluated: 2500 l/s (a), 8750 l/s (b) and 10,000
l/s (c).
Sustainability 2021, 13, 2980 15 of 20
Figure 11 shows that, for operating hours from 9 a.m. to 8.30 p.m., when a renovating
air flow of 8.750 l/s (scenario D.1.b) was considered, the result was 98% of ideal thermal
comfort hours (−0.5 < PMV < +0.5) and 2% of acceptable thermal comfort hours (−1 < PMV
< +1).
Figure 11. Comparison between scenarios A (current state) and D.1.a, D.1.b, D.1.c (MVR = Me-
chanical Ventilation with cooling) for the days of mid-August.
Figure 12 shows that for operating hours from 9 a.m. to 8.30 p.m. with a renovating
air flow of 2500 l/s (scenario D.1.a) acceptable thermal comfort can be achieved most of
the time, although 45 h surpass this situation. When the same renovating air flow but a
time schedule from 5 a.m. to 8.30 p.m. (scenario D.2.a) is considered, only 5 h exceed
Figure 12. Comparison between scenario A (current state), D.1.a (MVR, 2500 l/s, 9 a.m. to 8.30
p.m.) and D.2.a (MVR, 2500 l/s, 5 a.m. to 8.30 p.m.) for mid-August days.
Table 7 consists of a summary table of scenarios D, their percentage of thermal com-
fort, ideal or admissible, the occupancy hours under each comfort type and the improve-
ment with regard to the current state.
Sustainability 2021, 13, 2980 16 of 20
Table 7. Summary table of hours and percentage improvement for different D scenarios of MV+R.
2500 l/s
2500 l/s
8750 l/s
8750 l/s
10,000 l/s
10,000 l/s
9 a.m. to 8.30
5 a.m. to 8.30
9 a.m. to 8.30
5 a.m. to 8.30
9 a.m. to 8.30
5 a.m. to 8.30
PMV <= 0.5
Occupancy hours of ideal com-
3415 h 3606 h 4290 h 4290 h 4290 h 4290 h
0.5 < PMV < 1
Occupancy hours of acceptable
920 h 769 h 90 h 90 h 90 h 90 h
PMV > 1
Occupancy hours over accepta-
ble comfort 45 h 5 h 0 h 0 h 0 h 0 h
PMV <= 0.5
% occupancy hours ideal com-
fort 78% 82% 98% 98% 98% 98%
0.5 < PMV < 1
% occupancy hours acceptable
comfort 21% 18% 2% 2% 2% 2%
PMV > 1
% occupancy hours over ac-
ceptable comfort 1% 0% 0% 0% 0% 0%
% Improvement with regard to
current state 95.1% 99.5% 100% 100% 100% 100%
4. Discussion
As mentioned at the start of this paper, this historical building, with massive façade
walls 80 cm thick, high thermal inertia and natural ventilation during the summer, does
not behave as these kinds of buildings are thought to. Thermal comfort is not achieved,
although most studies, mentioned earlier in this paper, have noted the summer benefits
of thermal inertia. It has been verified that thermal conditions inside the temple during
the harshest days of this period, which coincide with the highest number of visitors, are
extremely sultry.
This is probably due to the extremely difficult renovation of inside air, and this effect
results from the very small difference between temperature and relative humidity indoors
with regard to temperature and relative humidity outdoors, as shown by onsite monitor-
ing. The reasons are multiple, for example the lack of tightness and insulation on the en-
velope that results in air leaks and high transmittance, particularly in the flat roofs that
have great solar gains during the summer months, and the simple glass of the stained-
glass gothic windows. Also, the small thermal oscillation throughout the day in this neigh-
borhood, between 3 and 5 °C, is a key issue. In fact, some authors have demonstrated that
energy saving, connected to the effects of thermal inertia and night ventilation, tends to
be more evident when thermal oscillation exceeds 10 °C, varying from small percentages
to more than 80% [15]. Neither must we forget the heat island effect, which usually pro-
vokes an increase of environmental night temperatures.
Some researchers suggest night ventilation to avoid indoors overheating during the
daytime [21,22]. In this case study, night ventilation is not an option due to risk of intru-
sion. This strategy is not always a feasible option for heritage buildings that house works
of art, so conditions that could make it suitable when night surveillance is not affordable
must be studied.
Sustainability 2021, 13, 2980 17 of 20
This assessment method to establish thermal comfort inside historical buildings that
have a large interior air volume demonstrated that acceptable thermal comfort for users
during summer months is not possible with natural ventilation alone. In these cases, no
other passive strategies can be developed if they affect the building envelope, as they
could alter the building’s cultural value. Consequently, the only possible solution is to
develop active strategies such as mechanical ventilation with cooling. In fact, to achieve
ideal thermal comfort during the summer months (PMV<+0.5) in the lower 3 m that cor-
responds to the air volume near users, ventilation air flows are required that are equal to
or greater than 8750 l/s from 9 a.m. to 8.30 p.m. However, greater tolerance of users, which
means acceptable comfort (PMV<+1) instead of ideal comfort for the same period of the
year but considering operating hours between 5 a.m. and 8.30 p.m., would allow ventila-
tion air flow to be reduced to 2500 l/s. The volume of air flow is not a minor issue, as larger
air flows imply higher energy consumption, increase of noise and bigger machines that
must be integrated inside the historical building, aspects that always have some kind of
impact on the user.
5. Conclusions
The method used to analyze thermal comfort inside historic buildings verifies the
hypotheses stated at the beginning of this paper.
Firstly, onsite monitoring showed that, for historic buildings located in Mediterra-
nean climates, characterized by a large RH and a small thermal amplitude, the thermal
discomfort level during the summer period is very high. In fact, it greatly exceeds the
thermal discomfort level of winter days.
The most common passive strategies to improve the energy performance behavior of
historic buildings are based on reducing the thermal transmittance of the envelope, pro-
tecting from solar gains and increasing the air tightness of the whole building. When the
building to be retrofitted is protected by law because of its historic and cultural values
and it has a bare “skin,” meaning masonry walls without coating, the only passive strat-
egy to improve thermal comfort is natural ventilation.
The dynamic simulation demonstrated that natural ventilation does not work
properly when the difference in hygrothermal conditions inside and outside the building
is very small. Mechanical ventilation does not work either. The only solution that solves
the envelope preservation and improves thermal comfort during summer months is me-
chanical ventilation with cooling.
The next step will necessarily be to study in-depth the impact of the facilities that
provide it. For this purpose, the collaboration of architects will be required who are spe-
cialized in heritage preservation and engineers experienced in the design of air-condition-
ing systems for large inside air volumes that are highly efficient. To minimize the size of
these machines, and therefore the consumption costs and the visual impact, the following
criteria, considered and verified by previous dynamic simulation, should be considered:
- To maintain stable conditions, it is preferable to choose the smallest machine func-
tioning for long periods of time rather than large machines functioning for short pe-
- The main aim is to attain thermal comfort for users, hence the systems to be used
must work on the air volume around users, which means the lower 3 m of the inside
air volume instead of the total height of the building. This is a feasible option when
cooling, as fresh air uses to stay in the lower layer.
- The thermal comfort degree can be less demanding (−1 < PMV <+ 1) as occupancy is
short term and users are more tolerant when they note the building’s historical value.
Another obvious criterion can be added that contradicts heritage authorities—when
active systems are required inside public buildings, renewable energies should be
used. As a consequence, a study of integration between historic building and captur-
ing systems of renewable sources must be developed.
Sustainability 2021, 13, 2980 18 of 20
At this point, we should consider whether this solution could be extrapolated to other
historical buildings with this typology. These are defined as buildings with large, high
inside spaces and large air volumes, like churches, factories or markets, characterized by
thick massive walls without insulation, high transmittance values for windows, roofs and
façades and, most importantly, with no opportunity to alter the building envelope, so as
to preserve its cultural value. The answer is that the thermal behavior of this kind of build-
ings has not been studied extensively. However, we can establish that this method to as-
sess and simulate the most suitable solution to improve energy performance and thermal
comfort is valid, since it has been successfully used to assess existing buildings, both his-
toric and modern, with different uses, areas, volumes and even different levels of cultural
protection [43,44].
In related and future research, some considerations must be taken into account.
To guarantee correspondence between real building’s thermal performance and its
simulation, it would be interesting to measure the real transmittance of the envelope ele-
ments with flowmeters. Some authors emphasize the complexity of obtaining accurate
data on the envelope, and the challenge of developing solutions that improve thermal
comfort without altering the documentary or cultural values of the building [13,45]. Some
researchers have already verified that thermal conductivity of the building envelope can
be much higher than stated in theoretical values [46,47].
After the building retrofitting, surveys and monitoring should be carried out to de-
termine the real degree of users’ thermal comfort.
Thermal comfort is not sufficient to achieve full wellbeing of people. The challenge
is to improve relations between the energy performance of the building and the indoor
environmental quality (IEQ) [48,49]. Occupant needs and behavior must be studied more
carefully [24].
Recent health circumstances associated with the COVID-19 pandemic have high-
lighted that appropriate air renovation inside public buildings is key to human health. As
Balocco et al. stated, the concept of sustainability should also be acknowledged as well as
people’s health, safety and wellbeing [44]. Therefore, considering the uncertain future
health situation, it is important to pay special attention to interior air quality, to install
mechanical ventilation and add detection and control systems to diagnose the presence of
microorganisms in a building’s internal atmosphere and on the internal surfaces of the
building construction elements [50]. However, even more important is the need to incor-
porate these systems as legal requirements.
Author Contributions: Conceptualization, B.O. and A.D.; methodology, B.O. and A.D.; formal
analysis, B.O. and A.D.; investigation, B.O. and A.D.; resources, B.O. and A.D.; data curation, B.O.
and A.D.; writing—review and editing, B.O. and A.D. All authors have read and agreed to the
published version of the manuscript.
Funding: This research received no external funding.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: Data available in a publicly accessible repository that does not issue
DOIs. This data can be found here:
Acknowledgments: The authors appreciate the contributions of J. Portal, Architect-Curator of Sta.
Maria del Mar, and the collaboration of Architect M. Tarrida with the dynamic simulation.
Conflicts of Interest: The authors declare no conflict of interest.
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... Therefore, the case study presented primarily a possible approach to establishing and assessing these tolerable ranges of short-term relative humidity fluctuations, which are, however, individual for each building. Onecha and Dotor [50] focused on one of the Barcelona basilicas. The first phase involved collecting basic data about the building, the environment, and the visitors. ...
... Temperature and relative humidity were measured in all churches. Furthermore, in some churches, the surface temperature of the Onecha and Dotor [50] focused on one of the Barcelona basilicas. The first phase involved collecting basic data about the building, the environment, and the visitors. ...
Full-text available
A suitable indoor climate positively affects the lifespan of historical building structures. The path to an agreeable climate begins with monitoring current conditions. Considerable attention is given to monitoring the indoor climate of historical buildings. The motivation for monitoring air temperature and surface temperatures, relative air humidity or airflow can be, for example, the installation of heating, the occurrence of biotic damage, and others. Through the analysis of the most frequently used keywords, a strong connection was found, for example, between thermal comfort and the church. This review also summarises the various reasons for conducting microclimate monitoring studies in historical religious buildings on the European continent. It is supplemented with an evaluation of the monitoring methodology from the chosen period of the year point of view, the measured parameters, and the length of the interval between the recordings of quantities. It was found that in more than one-third of the cases, the recording time was less than or equal to 15 min, but mostly less than or equal to 1 h. Quite often, monitoring results are used to calibrate a simulation model describing the hydrothermal behaviour of a historical object under various operation alternatives (e.g., influence of ventilation, climate change, occupancy, etc.). This way, it is possible to test various intelligent systems in the virtual world without much risk before they are used in an actual building application.
... For buildings that are used occasionally, such as cultural premises, a reduction rather than an exemption from these requirements could be understood. Adaptive thermal comfort and users understanding the priority of protecting cultural values during short visits may offset lower energy demands [5]. However, when continually used buildings like dwellings are considered, the exigence on energy efficiency is inescapable. ...
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In attempts to improve the energy efficiency of protected historical buildings, two barriers arise. The first is the restrictions imposed by authorities that are responsible for cultural heritage preservation. The second is the exclusion of protected buildings from strict compliance with energy efficiency requirements in current regulations, such as the issue of an Energy Performance Certificate, which removes them from conventional channels of public policies. Both of these issues put heritage in a delicate situation, especially when they are intended for privately developed residential uses. This paper presents a methodology for assessing and establishing a trade-off between energy performance and the cultural value of heritage buildings through the comprehensive analysis of a case study: the retrofitting of Can Armengol Palace in Palma de Mallorca (Spain). The study revealed (1) the need to objectify the cultural values of the building as far as possible to identify conflicts with the strategies of energy efficiency improvement; and (2) the appropriateness of considering every aspect of a rehabilitation intervention in a global simultaneous approach, not just energy aspects. The method that was used had five steps: acquiring a deep knowledge of the building configuration, assessing the building performance for every legal requirement, identifying cultural values, defining intervention criteria, and analyzing intervention effects on the protected elements of the building. The most important contribution in this study is the detailed and extended definition of architectural heritage values and the consideration of interventions resulting from sustainability retrofits as a new kind of value, that reflects current worries, for which future generations will remember us
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In higher-education world heritage sites, the conservation and energy retrofitting of heritage buildings (HBs) is an important vector for their development, competitiveness and welfare. To guarantee their ongoing use, these buildings must be adapted to face current and emerging societal challenges: (i) the conservation of cultural heritage and the maintenance of their original characteristics and identity; (ii) the transformation of heritage sites into tourist centers that energize the local economy, generating revenue and jobs; (iii) the adaptation of the buildings to new uses and functions that demand energy retrofitting strategies to satisfy today’s standards of thermal comfort, indoor environmental quality (IEQ) and energy efficiency; (iv) tackling impacts of climate change, particularly global warming and extreme weather events; and finally, (v) the implementation of strategies to mitigate the impact of a growing number of tourists. The combined implications of these challenges require a comprehensive approach with interrelated measures strongly reliant on the use of technology and innovation. This work aims to discuss how higher-education cultural HBs can be rethought to serve these expectations. Moreover, a multidisciplinary intervention framework is provided to discuss how HBs can respond to the challenges and risks of rehabilitation, energy retrofitting, climate change and increasing tourism.
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The COVID-19 pandemic has changed the engineering/technical approach to building and plant design. In Italy, most of the school heritage belongs to historical buildings, which are not only under constraints for the protection and prevention of loss of cultural heritage but are often created with a different intended use. This fact implies that any plant engineering project is really complex. Starting from the current sanitary measures for reopening during the Covid-19 era and the crucial current research on this matter, the feasibility of plant retrofit/refurbishment solutions by means of effective ventilation and air quality are investigated. Various plant solutions based on demand-controlled mechanical ventilation, operating 24 h a day, seven days a week, without air recirculation mode, for a historical high school building were studied using transient simulations. A result comparison showed that it is possible to obtain healthy school environments by means of an optimal compromise between energy savings and the best ventilation conditions for indoor air quality (IAQ). Sustainability is understood as effective and efficient solutions for energy consumption reduction and environmental sustainability as a guarantee for people’s safety and wellbeing.
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The study investigated the level of thermal comfort in historical buildings located at a relatively high altitude in the Arabian Desert of Saudi Arabia. The study focused on the impact of the use of thermal mass and orientation on the level of thermal performance at Shubra and Boqri Palaces. Qualitative and quantitative analyses were used in this study, including a questionnaire interview with architecture experts living at the relatively high altitude of Taif city, to obtain data and information from local experts. The computer software TAS EDSL was used along with on-site equipment, such as thermal imaging cameras and data loggers, to observe the physical conditions of the building in terms of its thermal performance. The study revealed that the experts' age and years of experience were important aspects while collecting data from them during the survey. The use of thermal mass had a slight impact on the indoor air temperature as well as the energy consumption, but it helped in providing thermal comfort. Use of ventilation can improve thermal comfort level. Evaporative cooling technique has a considerable impact on reducing indoor air temperature with 4 °C drop, improving the thermal comfort sensation level. The novelty of this work is that, it links the outcomes of qualitative results of experts with field monitoring as well as computer modelling. This can contribute as method to accurately collect data in similar case studies.
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Historic buildings account for more than one-quarter of Europe’s existing building stock and are going to be crucial in the achievement of future energy targets. Although a drastic reduction in carbon emissions would slow climate change, an alteration in the climate is already certain. Therefore, the impact of climate change on retrofitted historic buildings should be considered in terms of occupants’ comfort, heritage conservation, and energy performance. Inappropriate interventions might weaken the potential of traditional climate adaptive solutions, such as thermal mass and night cooling, leading to higher risks of overheating in a warming climate. Similarly, retrofit solutions will change the moisture dynamics of historic envelopes, which might lead to moisture damages when combined with more extreme precipitation events. This paper reviews recent literature that provides evidence of climate change’s impact on retrofitted buildings, reveals potential future risks, and thereby sheds light on new factors influencing the decision-making process in the retrofit of historic buildings.
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La cultura de la conservación y de la sostenibilidad del medio ambiente se caracteriza por raíces comunes que han dado lugar a una convergencia de objetivos, prácticas, métodos y herramientas. Ambas tienen como objeto de investigación el patrimonio cultural, un importante “recurso no renovable” que ha de ser valorizado a través de acciones compatibles con su valor histórico. Hay muchas razones para considerar la conservación y la recuperación de las viviendas históricas como una estrategia de desarrollo sostenible. De hecho, en muchos casos, los edificios históricos se encuentran en zonas densamente pobladas y equipadas con infraestructuras que responden ecológicamente a usos muy intensos. En general, los edificios son hechos con materiales locales y duraderos y se construyen después de un estudio detallado del medio ambiente, con el fin de explotar el potencial de los recursos naturales y renovables. Por eso, su recuperación tiene un alto porcentaje de embodied energy, que se puede definir como la cantidad de energía necesaria para extraer, recuperar y reutilizar materiales, objetos y edificios.
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In recent years, the interest in properly conditioning the indoor environment of historic buildings has increased significantly. However, maintaining a suitable environment for building and artwork preservation while keeping comfortable conditions for occupants is a very challenging and multi-layered job that might require a considerable increase in energy consumption. Most historic structures use traditional on/off heating, ventilation, and air conditioning (HVAC) system controllers with predetermined setpoints. However, these controllers neglect the building sensitivity to occupancy and relative humidity changes. Thus, sophisticated controllers are needed to enhance historic building performance to reduce electric energy consumption and increase sustainability while maintaining the building historic values. This study presents an electric cooling air controller based on a fuzzy inference system (FIS) model to, simultaneously, control air temperature and relative humidity, taking into account building occupancy patterns. The FIS numerically expresses variables via predetermined fuzzy sets and their correlation via 27 fuzzy rules. This intelligent model is compared to the typical thermostat on/off baseline control to evaluate conditions of cooling supply during cooling season. The comparative analysis shows a FIS controller enhancing building performance by improving thermal comfort and optimizing indoor environmental conditions for building and artwork preservation, while reducing the HVAC operation time by 5.7%.
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In the Mediterranean climate, indoor overheating and, thus, excessive use of cooling systems represents one of the main problems both for the occupants' health and energy consumption. In order to limit this problem, an appropriate design or energy retrofitting of the building envelope is of utmost importance. The predominance of massive buildings in the Italian territory and the need to comply with Italian regulations often leads technicians to not optimal energy saving solutions. To this purpose, this experimental research was conducted on a mockup building, located in Fabriano and characterized by high thermal mass walls (W0) and two different external insulating systems: Cork based lightweight plaster (W1) and Extruded polystyrene foam panel (XPS) (W2). Furthermore, a virtual model in TRNSYS, a transient simulation software, was used to compare analytical and simulated values. Results show that W2 undergoes a higher level of thermal stress than W1, due to higher peaks in the external surface temperature and larger fluctuations in daily temperature. Therefore, a high value of thermal resistance of the external insulation and low value of external areal heat capacity on a massive building causes external surface overheating problems, thus, not representing the optimal construction solution.
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There are indications that energy-retrofitted buildings can create risks for indoor environmental quality (IEQ) and therefore for health and comfort of occupants. A review was conducted to identify and verify those risks, within three themes: building envelope, heating, ventilating and air conditioning (HVAC)-systems, and occupants. Publications from the last five years in major peer-reviewed journals from different fields (energy, buildings, indoor air, social sciences) were found by using a variety of keywords (health effects, occupant behaviours, energy-efficient retrofitting, etc.). For the building envelope, retrofitted buildings tend to be air-tighter and more thermally insulated. Hence, humidity problems, build-up of pollutants, and overheating may occur. Installing HVAC-systems and issues within (ducts, filters, maintenance, noise) may also compromise IEQ. Although relationships are difficult to establish, evidence shows that certain retrofits increase the risk of health problems, particularly for airways, skin, and eyes. Despite the installation of energy-retrofitting technologies, not all buildings lower their energy consumption. This is partly due to occupants (behaviours, preferences, needs, awareness) and partly due to technical issues. The studies reviewed, mainly focused on the performance gaps of energy-retrofitted homes and on energy-saving measures. “Comfort” and “health” tend to be disregarded, with both being seldom measured and only assessed by simulation. Occupant behaviours, preferences, and needs are understudied and need to be incorporated into the research and development of retrofitting measures. More interdisciplinary approaches are needed, in which buildings & HVAC-systems, occupants, health and comfort, and IEQ are investigated as interacting elements and based on an integrated approach.
Climate change will affect the indoor temperature of historic buildings, impacting the preservation of artworks and the thermal comfort of users, and possibly leading to increased energy consumption. These buildings generate more emissions than new buildings and in most European countries, preservation principles take precedence over energy efficiency and the reduction of emissions. This research is a key topic for the mitigation of climate change and proposes a method for assessing the impact of climate change on the preservation of artworks, thermal comfort, and energy consumption. An experimental method was followed, combining analytical formulations, on-site measurements, and Heating, Ventilation and Air Conditioning systems in order to identify the adequate hygrothermal parameters for historic buildings. The climate change scenario predicted for 2050 was based on projected temperature variation. The case studies were Baroque churches, historic buildings located in the south of Europe. Data obtained from a monitoring campaign carried out in these churches was used to validate dynamic simulation models. The churches analysed showed an increase in cooling demand and a decrease in heating demand. Furthermore, in order to ensure human comfort and the preservation of artworks, it was necessary to implement active systems in operation for 12-hour periods. These results suggest an energy overconsumption, as the energy consumption for human comfort and artwork preservation was 50% higher than the energy consumption of active systems for the preservation of valuable historic objects. In addition, the annual energy consumption decreases for future scenarios for 2050 in the case of artwork preservation and thermal comfort, but increases by almost 15% for the preservation of works of art due to higher level relative humidity. Before historic buildings can be adapted, it is essential to understand the influence of the future climate on their design, construction, and environmental conditions.
Among the policies and regulations aimed at reducing the energy use in building stocks, the retrofit of historic buildings is one of the hardest challenges both for research and practice, because it is necessary to combine the traditional energy/economy targets with safeguard programs and conservation theories. In this paper, a decision support system is developed in order to plan and manage energy retrofit campaigns tailored for cultural heritage. Costs and energy uses are assessed, as well as the compatibility of interventions and their impact on indoor environmental quality. The energy use is seen under an economic, environmental, human and cultural perspective, providing a decision-making procedure that could be very useful for asset holders, public or private investors as well as for portfolio managers or agencies. The most important achievements in this work are the assessment of a so-called restoration score as a way to include conservation aspects in the selection procedure, and the integration of different appraisal techniques such as multi-attribute analysis, life cycle costing and analytic hierarchy process.