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congresso da reabilitação do património | crepat 2017
FICHA TÉCNICA
EDITORES
Aníbal Costa
Ana Velosa
Alice Tavares
PAGINAÇÃO E MONTAGEM
Briefing
CAPA
Ana Sofia Almeida (UA)
IMPRESSÃO
Tipografia A Lusitânia
TIRAGEM
200 exemplares
EDIÇÃO
1ª Edição - junho de 2017
ISBN
978-989-20-7623-2
DEPÓSITO LEGAL
428009/17
Os textos são da exclusiva responsabilidade dos seus autores.
© Os autores. 2017
© Os editores. 2017
Universidade de Aveiro – Departamento de Engenharia Civil
Campus Universitário de Santiago | 3810-193 Aveiro
375
Tema 5 | Compatibilização - eficiência energética versus reabilitação
Estudo do desempenho térmico e avaliação
das condições de conforto em edifícios antigos:
casos de estudo do município de Ovar
__
Study of thermal performance and evaluation of
comfort conditions in ancient buildings: case studies
from the Portuguese municipality of Ovar
Jorge Fernandes1, Alice Tavares2, Ricardo Mateus3, Helena Gervásio4, Aníbal Costa5
1Centro de Território, Ambiente e Construção (C-TAC), Universidade do Minho. jepfernandes@me.com
2RISCO, Departamento de Engenharia Civil, Universidade de Aveiro. tavares.c.alice@ua.pt
3Centro de Território, Ambiente e Construção (C-TAC), Universidade do Minho. ricardomateus@civil.uminho.pt
4Institute for Sustainability and Innovation in Structural Engineering (ISISE), Universidade de Coimbra. hger@dec.uc.pt
5RISCO, Departamento de Engenharia Civil, Universidade de Aveiro. agc@ua.pt
Resumo
A última transposição para a legislação portuguesa da diretiva europeia sobre o desempenho
energético de edifícios (EPBD), aumentou consideravelmente os requisitos exigidos tanto a edi-
fícios novos como a reabilitações. Nos edifícios antigos, as características arquitetónicas e dos
materiais existentes condicionam as soluções disponíveis. A solução de reabilitação energética
mais eficaz passa muitas vezes por identificar e combinar estratégias que conduzam à solução
de custo-ótimo. Para identificar as melhores opções dentro das linhas de intervenção possíveis
(à escala das envolventes; estratégias passivas; equipamentos; sistemas de energia renovável),
por forma a otimizar a intervenção e a melhorar o desempenho térmico e as condições de
conforto, é necessário perceber o real desempenho deste tipo de edifícios.
Neste âmbito, este artigo apresenta os resultados preliminares do estudo de desempenho tér-
mico e de conforto de um conjunto de casos de estudo localizados em Ovar. As monitorizações
incluíram a medição de parâmetros higrotérmicos e inquéritos sobre a sensação térmica dos
ocupantes.
Palavras-chave
Desempenho térmico; avaliação de conforto; monitorização; edifícios antigos
Abstract
The latest transposition into Portuguese legislation of the European Directive on the energy
performance of buildings (EPBD) has considerably increased the requirements for both new
buildings and rehabilitation. In old buildings, architectural and existing materials features
condition the available solutions. The most effective energetic refurbishment solution often
involves identifying and combining strategies that lead to a cost-optimal solution. To identify
the best options within the possible lines of action (at the scale of the envelope, passive strate-
gies, equipment, renewable energy systems), in order to optimize the intervention and improve
thermal performance and comfort conditions, it is necessary to perceive the real performance
of this type of buildings. Therefore, this paper presents the preliminary results of the study on
thermal performance and comfort of a set of case studies located in Ovar. Monitoring included
the measurement of hygrothermal parameters and surveys on occupants’ thermal sensation.
Keywords
Thermal performance; Comfort assessment; monitoring; old buildings.
376 congresso da reabilitação do património | crepat 2017
1. Introduction
The building sector is changing to a paradigm of energy-efficiency and environmental awa-
reness. In fact, buildings are a key sector to implement energy and environmental measures,
since it is one of the largest energy and natural resources consuming sectors [1], responsible
for a third of global total CO2 emissions [2]. In the European Union (EU), for example, this
change of paradigm is driven by the goals set in EU Directives. The directives on the Energy Per-
formance of Buildings (EPBD) [3] and Energy Efficiency [4] have set the EU targets of saving 20%
of primary energy consumption by 2020 and reducing greenhouse gas emissions by 80-95% by
2050 compared to 1990. Therefore, to accomplish the targets, new high-performance building
concepts have been defined, as the “nearly zero-energy buildings” (nZEB), where energy de-
mand must be offset by renewable energy sources [3]. The first steps to achieving a high-per-
formance building are a reduction in energy demand for HVAC, by optimizing solar orientation
and built form and by increasing envelope’s insulation levels. Nevertheless, these actions are
not always simple to implement in the existing building stock. Thus, in existing buildings,
the most cost-effective renovation solutions are frequently a combination of energy-efficiency,
energy conservation, and carbon emissions reduction measures. In the case of Portugal, accor-
ding to Ferreira et al. [5], the housing stock built in the 1990s can move to a nearly zero-energy
building scenario without major difficulties, considering the introduction of renewables on
buildings that meet the cost-optimal levels. However, in the case of old buildings, traditional
building materials and architectural features limit the range of available solutions. The most
effective energy-renovation solution is frequently a combination of the best strategies that
lead to a cost-optimal solution. Therefore, for each building, there is the need to identify the
best solutions within the possible actions (envelope; passive strategies; equipment, renewable
energy systems). The diversity of traditional construction systems found in Portuguese archi-
tecture makes necessary to understand the real performance of this type of buildings. With
this information is possible to perceive how they can be improved to meet the new require-
ments of energy and thermal performances, and optimize the renovation operation.
In this sense, this paper aims at contributing to the research field by presenting the prelimi-
nary results of the study of thermal performance and comfort priorities in a set of building
case studies located in the Ovar municipality. The study included in-situ measurements of
hygrothermal parameters and surveys on occupant thermal sensation.
2. Geography, climate, and architecture in Ovar
Ovar is a small town located in the district of Aveiro, in the centre region of Portugal. Once a
fishing and salt port [6], [7], the town lost this function due to the progressive retreat of the sea
line during centuries and is now at approximately 4,5 km far from the coastline. The town is
implanted in a flat area with a valley and is divided by a small river, formed by the confluence
of two brooks that flow into the Aveiro Estuary. Ovar has a sprawled urban mesh characterised
by buildings mainly with 1 or 2 floors. Presently, there are several buildings from the 19th and
beginning of the 20th centuries, as the case studies presented in this paper. This bourgeoisie
architecture has normally symmetrical facades design with a high front door in the center. The
period of construction reflects the preferences at the time, in a moment of return of Portuguese
entrepreneur from Brazil (as the case of Costa’s house with a characteristic platband), but
also a crescent capacity of builders through the implementation of railway which brought the
opportunity of more accessible construction materials, as the granite applied on the facades.
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Tema 5 | Compatibilização - eficiência energética versus reabilitação
The town is implanted on sandy soil. However, the soils from nearby areas at East are not only
very fertile but characterized by the presence of gravel, phyllite, and schists associated to luvi-
sols (i.e. soils that are rich in clay) [8]. In the absence of proper stone for building conventional
masonry [6], local population had to use the locally-available resources as building materials.
Soil’s features determined the materials and the building’s systems used. Thus, the most wi-
despread materials/building systems in Ovar’s architecture are walls built with adobe or with
a mix of small stones (or gravel) with clay (Fig. 1).
The climate of Ovar is influenced by the proximity to the Atlantic Ocean. The region has a
temperate climate, sub-type Csb according to Köppen climate classification, characterised by
rainy winters and dry or temperate summers [9]. The annual average mean air temperature
is of 15ºC, being of 12,5ºC in Winter and of 20ºC in Summer [9]. Regarding precipitation, the
annual average number of days with precipitation ≥ 1 mm is of 125, while the annual average
total rainfall is of 1000 mm, being December the month with the highest values and July the
driest month [9].
Figure 1. Materials used in Ovar’s constructions. (left) mix of stone gravel and clay wall; (right) adobe wall.
3. Methodology
The methodology adopted in this study aims to understand the thermal performance and
comfort of dwellings with the same typology, built with the same building materials and in the
same climatic zone, and establish a relation between occupant’s perception and expectation
regarding their comfort. To assess indoor thermal performance and comfort conditions of the
case studies, in-situ assessments were divided into short and long-term monitoring. The short-
-term monitoring was carried out at least one time per season of the year and consisted of ob-
jective and subjective measurements. The objective measurements were performed with the
purpose of quantitatively assess the thermal conditions within a specific room using a thermal
microclimate instrument (model Delta OHM 32.1), in compliance with standards ISO 7726 [10]
and ISO 7730 [11]. The location of the equipment is chosen according to occupants’ distribution
in the room. This data is used in the analysis of the thermal comfort conditions to determine
the operative temperature, namely in the adaptive model of thermal comfort, as explained
below. Simultaneously, were carried the subjective measurements, i.e., evaluate environment
conditions by surveying the occupants. The survey allows to assess occupants’ satisfaction
according to ASHRAE thermal sensation scale and was based on the “Thermal Environment
Survey” from ASHRAE standard 55 [12]. The surveys were carried for the rooms that occupants
378 congresso da reabilitação do património | crepat 2017
considered more comfortable and/or where they spend more time. The long-term monitoring
was aimed at understanding the fluctuations of air temperature and relative humidity profiles,
indoors and outdoors, throughout the various seasons in compliance with specified procedures
and standards [10]–[12]. For this purpose, thermo-hygrometer sensors were installed outdoors
and indoors, set to record data at 30 min intervals. During these measurements, occupants
fulfilled an occupancy table where they recorded how they had used the building, i.e., if they
used heating or cooling systems, promoted ventilation, etc.
Thermal comfort conditions were evaluated considering an adaptive model of thermal com-
fort, the most adequate for naturally conditioned areas. In order to be more representative of
the Portuguese reality, the chosen model was the one developed in the National Laboratory of
Civil Engineering (LNEC) by Matias [13]. In this model, thermal comfort is only verified when a
person feels neutral and simultaneously shows preference to keep that neutrality. The thermal
environment condition point is determined using a chart that correlates Operative tempera-
ture (Θo) with Outdoor running mean temperature (Θrm).
4. Thermal performance study and comfort conditions assessment
4.1 Description of the case studies
4.1.1 Case study 1 – Costa’s house
Case study 1 is on the East side of the town. The building is integrated into the urban mesh, in
a group of buildings forming a small public square. Its facades are facing north, west (street)
and east (courtyard). The gross floor area is approximately 250 square meters divided into two
storeys. In the ground floor, there are the living room, the garage and storage rooms. In the
first floor, at West are the bedrooms and at East the dining room and the kitchen (Fig. 2). It was
not possible to determine exactly the date of construction but, according to the owners, it is
probably from the 19th century. Regarding the building systems, it was not possible to deter-
mine the materials used in the building. Nevertheless, it is highly probable that the materials
used are the most common in this type of buildings in Ovar, as above mentioned. Thus, the
building envelope consists of walls built with a mix of small stones and clay (average thickness
of 60cm), with a pitched roof, wooden doors and wooden framed single glazed windows in the
main façade and aluminium framed double glazed windows in the rear facade. Indoors, the
partitions walls are in tabique – a wooden framed structure where the spaces between studs are
fulfilled with small stones, bricks or clay.
Figure 2. (left) External view; (right) Floor plans showing the position of measuring instruments (1—
living room; 2—bedroom; 3—dining room; 4—kitchen).
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Tema 5 | Compatibilização - eficiência energética versus reabilitação
4.1.2 Case study 2 – Begasse’s house
Case study 2 is on the West side of the town. The building is a detached house and its facades
are facing north (courtyard), south (street), west and east. The gross floor area is approximately
230 square meters divided into two storeys. On the ground floor are the living room, technical
room and the storage room. On the first floor, at south are the main bedrooms and at north the
kitchen (Fig. 3). It was not possible to determine the date of construction but, according to the
owners, it is probably from the 20th century. The building envelope consists of walls built with
a mix of small stones and clay (average thickness of 65cm), with a pitched roof, wooden doors
and wooden framed single glazed windows. Indoors, the partitions walls are in tabique.
Figure 3. (left) External view; (right) Floor plans showing the position of measuring instruments (1—
living room; 2—bedroom 2; 3—bedroom1; 4—kitchen; 5—bedroom3).
4.2 Hygrothermal monitoring and comfort assessment
The thermal performance monitoring was carried out for all seasons of the year. However, in
this paper, only the results obtained for the two most demanding seasons in what thermal
comfort is concerned, i.e., winter and summer, are addressed and discussed. The summer mo-
nitoring was conducted over the period from 21st June to 19th September 2016 and the winter
monitoring over the period from 21st December to 3rd February 2017.
4.2.1 Summer monitoring
From the analysis of the results, it is possible to verify that during summer, outdoor mean air
temperature was of about 21°C. The maximum air temperature was around 25°C in most of the
days, surpassing 30ºC in some days. Minimum air temperature during the monitoring period
was of about 14ºC. Outdoor mean relative humidity was around 70% while maximum and
minimum values were around 90 and 30%, respectively.
In case study 1, indoor rooms showed a stable air temperature profile (Fig. 4). During all the
monitoring period, the mean air temperature in indoor rooms was around 22-24°C. In the be-
droom, the maximum air temperature was higher than in other rooms, probably due to solar
exposure of the main facade (west) and also by the higher heat transfer coefficient of the sin-
gle-glazed windows. In opposition, the living room had a maximum air temperature between
3-5ºC lower than the other monitored rooms (Fig. 4). The high thermal inertia of walls and floor
and the fact that it has less glazed area, is probably the reason for the milder temperature
380 congresso da reabilitação do património | crepat 2017
profile when compared with the remaining upper floor rooms. In case study 2, indoor moni-
toring results show that all the inhabited rooms have a stable temperature profile, with mean
values around 22-23ºC (Fig. 4), and maximum and minimum temperatures within thermal
comfort range values most of the time. The living room had the most stable profile with higher
minimum temperature (20.4ºC) and lower maximum temperature (25ºC). Its position on the
ground floor, partially buried, and the high mass walls allow stabilizing the temperature. In
both cases studies, beyond the thermal inertia, all the indoor rooms are naturally ventilated
during the morning, what contributes for removing heat loads and cool the house.
Regarding the relative humidity (Fig. 5), for both case studies, the indoor mean values recorded
are high and between 60-70% for all rooms, above of what it is recommended (between 40-60%
[14]). The profiles are stable with slight daily variations in some rooms, probably due to the
opening of windows and doors for ventilation. During the days with lower outdoor relative hu-
midity, indoor values were higher. This is certainly due to the hygroscopic inertia of the walls,
made of earthen materials.
The assessment of the summer season comfort conditions was done in case study 1 for the
kitchen/dining room and in case study 2 for the living room (Fig. 6). In both cases, from the
analysis of the charts, it was found that the rooms had a comfortable thermal environment,
within the comfort range but close to the lower limit. In the subjective assessment carried out,
two occupants showed to be “neutral” (comfortable) and one as “slightly cool” in the thermal
sensation scale, confirming the objective measurements. Although the results from the short-
-term measurements represent one day, the conditions of thermal comfort can be extrapolated
to almost all days, since there is a strong relation of dependency between the air temperature
and the operative temperature [13].
Figure 4. Indoor and outdoor air temperature profiles during summer season. (left) Case Study 1;
(right) Case Study 2
Figure 5. Indoor and outdoor relative humidity profiles during summer season. (left) Case Study 1;
(right) Case Study 2
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Tema 5 | Compatibilização - eficiência energética versus reabilitação
Figure 6. Adaptive comfort chart for summer monitoring without heating/cooling systems. (left) Case
study 1 – Thermal comfort temperature (operative temperature) in the dining room/kitchen; (right)
Case study 2 – Thermal comfort temperature
(operative temperature) in the living room.
4.2.2 Winter monitoring
During the monitoring, outdoor mean air temperature was of about 9°C. The maximum air
temperature was around 17°C but in most of the days was around 12-13ºC. The minimum air
temperature during the monitoring period was of 0ºC. Outdoor mean relative humidity was
around 85% while maximum and minimum values were around 100 and 47%, respectively.
In case study 1, indoor rooms showed air temperature profiles below 18ºC during the moni-
toring (Fig. 7), with mean values between 12-14ºC. Maximum air temperature in dining room/
kitchen and bedroom was around 18-19ºC. The relative stability in these rooms was due to the
thermal inertia but also to the use of portable electric heaters that were frequently switched on
during the monitoring. In case study 2, the indoor temperature profiles (Fig. 7) show significant
variations in regular periods of time. These variations and temperature peaks are due to the
occupation profile, i.e, the house is permanently occupied mainly three days per week, and in
those days temperature rises very rapidly when the central heating system is activated. When
the heating system is turned off, air temperature decreases slowly through the following days
until “stabilizes” around maximum outdoor temperature values, however, low. In this case, the
use of the central heating system (boiler + radiators) allowed maintaining indoor temperature
within comfort range values. However, in case study 1, is possible to see that the type of heating
system used was not enough to ensure comfort conditions in most of the days. Considering the
relative humidity, for both cases indoor spaces had relatively stable profiles with mean values
between 60-70% (Fig. 8). In case study 2, when the heating system is activated, values de-
creased and stabilized between 40-60%, a boundary that is adequate for human health. In this
case, the living room has the lower values, but this is due to the use of a dehumidifier device.
Although the values recorded for both cases are high for a healthy indoor environment, are
stable and considerably lower than those recorded outdoors. It is also possible to verify that the
mean values between the two seasons are very similar. Climatic factors, namely the influence
of the ocean, is a strong reason for frequent high relative humidity values.
382 congresso da reabilitação do património | crepat 2017
Figure 7. Indoor and outdoor air temperature profiles during winter season. (left) Case Study 1; (right)
Case Study 2.
Figure 8. Indoor and outdoor relative humidity profiles during winter season. (left) Case Study 1;
(right) Case Study 2.
The assessment of the winter season comfort conditions was done in case study 1 was done in
case study 1 for the kitchen/dining room and in case study 2 for the living room (Fig. 9). In case
study 1, the kitchen/dining room had a thermal environment in the lower limit of the comfort
range, even with heating equipment turned on. In the subjective assessment, three occupants
answered as being “neutral” (comfortable) and two as “slightly warm”. Although the objective
measurements show that room’s environment is in the lower limit of the comfort range, two
occupants answered as being “slightly warm”, in the opposite limit. The explanation for this
result is that these occupants were the ones closest to the electric heater. In case study 2, with
the heating system activated, the living room had a good thermal environment (Fig. 9). In the
subjective assessment, two occupants answered as being “slightly warm”, one as being “hot”
and one as being “slightly cool” in the thermal sensation scale. Although the objective measu-
rements showed that the room had a good thermal environment, almost in the middle of the
comfort range, none of the occupants answered as being comfortable. This result has several
explanations. The first is the thermal resistance of clothes, the second is that one occupant
was closest to the heat radiator and the other was the closest to the external wall, being the
two influenced by the radiation effect, one receiving heat from the radiator and the other
losing heat to the cool wall. The measurements in the two cases reflect the complexity of as-
sessing thermal comfort and the importance of choosing an adequate point for performing the
measurements, they also show the difference between occupants and the need to perform longer
measurements in order to force occupants to adapt their clothes to the environment they are in.
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Tema 5 | Compatibilização - eficiência energética versus reabilitação
Figure 9. Adaptive comfort chart for winter monitoring with heating system. (left) Case study 1 –
Thermal comfort temperature (operative temperature) in the dining room/kitchen; (right) Case study
2 – Thermal comfort temperature (operative temperature) in the living room.
5. Conclusions
The preliminary results of the thermal environment monitoring carried out in the two case
studies, support that was possible to achieve indoor thermal comfort during cooling season
by passive means alone. During winter, in both case studies, indoor thermal conditions were
below the comfort range and the periods of thermal discomfort had to be overcome by using
heating systems. It was observed that indoor temperature and relative humidity profiles were
relatively stable in both seasons. The thermal and hygroscopic inertia of the envelope, mainly
schist+clay and adobe walls with thickness between 0.50-0.65cm, has a positive influence in
this behaviour. An example is case study 2, where after turning off the heating system, air
temperature takes about a week to decrease to the previous levels. The surveys on occupants’
thermal comfort corroborated the objective assessments, although with some discrepancies in
winter assessment. It should be noted occupants’ action in the regulation of their comfort con-
ditions (e.g., promotion of morning ventilation during the summer period). Therefore, this is
an on-going research work that intends to collect more detailed data of a set of 4 case studies,
in order to understand their thermal performance and identify energy-efficiency renovation
solutions that can improve comfort conditions.
Acknowledgments
The authors would like to acknowledge the support granted by the Portuguese Foundation
for Science and Technology (FCT), in the scope of the Doctoral Program Eco-Construction and
Rehabilitation (EcoCoRe), to the Ph.D. scholarship with the reference PD/BD/113641/2015 and
to postdoctoral support with the reference SFRH/BPD/113053/2015, that were fundamental for
the development of this study. The authors also wish to thank the owners of case study buil-
dings, Mr. Costa and Mr Begasse, for helping and supporting this research work.
384 congresso da reabilitação do património | crepat 2017
References
[1] B. Berge, The Ecology of Building Materials, 2nd ed., Oxford: Elsevier, 2009.
[2] D. Ürge-Vorsatz, L. D. Danny Harvey, S. Mirasgedis, and M. D. Levine, “Mitigating CO2 emissions
from energy use in the world’s buildings,” Build. Res. Inf., vol. 35, no. 4, pp. 379–398, Aug. 2007.
[3] European Parliament and of the Council, “Directive 2010/31/EU of the European Parliament and of
the Council of 19 May 2010 on the energy performance of buildings,” Strasbourg, 2010.
[4] European Parliament and of the Council, “Directive 2012/27/EU of the European Parliament and of
the Council of 25 October 2012 on energy efficiency, amending Directives 2009/125/EC and 2010/30/
EU and repealing Directives 2004/8/EC and 2006/32/EC,” Strasbourg, 2012.
[5] M. Ferreira, M. Almeida, A. Rodrigues, and S. M. Silva, “Comparing cost-optimal and net-zero
energy targets in building retrofit,” Build. Res. Inf., vol. 44, no. 2, pp. 188–201, Feb. 2016.
[6] A. Pinho Leal, Portugal antigo e moderno: diccionario geographico, estatistico, chorographico,
heraldico, archeologico, historico, biographico e etymologico de todas as cidades, villas e freguezias
de Portugal e de grande numero de aldeias. Vol. 6. Lisboa: Livraria Editora Mattos Moreira &
companhia, 1873.
[7] M. Oliveira, Ovar na Idade Média. Ovar: Câmara Municipal de Ovar, 1967.
[8] APA, “Atlas Digital do Ambiente. SNIAmb - Sistema Nacional de Informação de Ambiente.” [Online].
Available: http://sniamb.apambiente.pt/Home/Default.htm. [Accessed: 09-Mar-2017].
[9] AEMET and IM, Atlas Climático Ibérico: Temperatura do Ar e Precipitação (1971-2000)/Iberian
Climate Atlas: Air Temperature and Precipitation (1971/2000). 2011.
[10] ISO7726, “Ergonomics of the thermal environment e instruments for measuring physical
quantities,” 2002.
[11] ISO7730, “Ergonomics of the thermal environment: Analytical determination and interpretation
of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort
criteria,” 2005.
[12] ASHRAE, “ANSI/ASHRAE Standard 55 – Thermal Environmental Conditions for Human
Occupancy,” Atlanta, 2010.
[13] L. Matias, TPI65 - Desenvolvimento de um modelo adaptativo para definição das condições de
conforto térmico em Portugal. Lisboa: Laboratório Nacional de Engenharia Civil/National Laboratory
of Civil Engineering, 2010.
[14] T. Morton, Earth masonry – design and construction guidelines. Berkshire: HIS BRE Press, 2008.
Estudo do desempenho térmico e avaliação das
condições de conforto em edifícios antigos: casos de
estudo do município de Ovar
Study of thermal performance and evaluation of
comfort conditions in ancient buildings: case studies
from the Portuguese municipality of Ovar
Jorge Fernandes
Centro de Território, Ambiente e Construção (C-TAC), Universidade do Minho.
jepfernandes@me.com
Alice Tavares
RISCO, Departamento de Engenharia Civil, Universidade de Aveiro.
tavares.c.alice@ua.pt
Ricardo Mateus
Centro de Território, Ambiente e Construção (C-TAC), Universidade do Minho.
ricardomateus@civil.uminho.pt
Helena Gervásio
Institute for Sustainability and Innovation in Structural Engineering (ISISE),
Universidade de Coimbra. hger@dec.uc.pt
Aníbal Costa
RISCO, Departamento de Engenharia Civil, Universidade de Aveiro. agc@ua.pt
Resumo
A última transposição para a legislação portuguesa da diretiva europeia sobre o
desempenho energético de edifícios (EPBD), aumentou consideravelmente os
requisitos exigidos tanto a edifícios novos como a reabilitações. Nos edifícios antigos,
as características arquitetónicas e dos materiais existentes condicionam as soluções
disponíveis. A solução de reabilitação energética mais eficaz passa muitas vezes por
identificar e combinar estratégias que conduzam à solução de custo-ótimo. Para
identificar as melhores opções dentro das linhas de intervenção possíveis (à escala das
envolventes; estratégias passivas; equipamentos; sistemas de energia renovável), por
forma a otimizar a intervenção e a melhorar o desempenho térmico e as condições de
conforto, é necessário perceber o real desempenho deste tipo de edifícios.
Neste âmbito, este artigo apresenta os resultados preliminares do estudo de desempenho
térmico e de conforto de um conjunto de casos de estudo localizados em Ovar. As
monitorizações incluíram a medição de parâmetros higrotérmicos e inquéritos sobre a
sensação térmica dos ocupantes.
Palavras-chave
Desempenho térmico; avaliação de conforto; monitorização; edifícios antigos.
2
Abstract
The latest transposition into Portuguese legislation of the European Directive on the
energy performance of buildings (EPBD) has considerably increased the requirements
for both new buildings and rehabilitation. In old buildings, architectural and existing
materials features condition the available solutions. The most effective energetic
refurbishment solution often involves identifying and combining strategies that lead to a
cost-optimal solution. To identify the best options within the possible lines of action (at
the scale of the envelope, passive strategies, equipment, renewable energy systems), in
order to optimize the intervention and improve thermal performance and comfort
conditions, it is necessary to perceive the real performance of this type of buildings.
Therefore, this paper presents the preliminary results of the study on thermal performance
and comfort of a set of case studies located in Ovar. Monitoring included the
measurement of hygrothermal parameters and surveys on occupants’ thermal sensation.
Keywords
Thermal performance; Comfort assessment; monitoring; old buildings.
1. Introduction
The building sector is changing to a paradigm of energy-efficiency and environmental
awareness. In fact, buildings are a key sector to implement energy and environmental
measures, since it is one of the largest energy and natural resources consuming sectors
[1], responsible for a third of global total CO2 emissions [2]. In the European Union (EU),
for example, this change of paradigm is driven by the goals set in EU Directives. The
directives on the Energy Performance of Buildings (EPBD) [3] and Energy Efficiency
[4] have set the EU targets of saving 20% of primary energy consumption by 2020 and
reducing greenhouse gas emissions by 80-95% by 2050 compared to 1990. Therefore, to
accomplish the targets, new high-performance building concepts have been defined, as
the “nearly zero-energy buildings” (nZEB), where energy demand must be offset by
renewable energy sources [3]. The first steps to achieving a high-performance building
are a reduction in energy demand for HVAC, by optimizing solar orientation and built
form and by increasing envelope’s insulation levels. Nevertheless, these actions are not
always simple to implement in the existing building stock. Thus, in existing buildings,
the most cost-effective renovation solutions are frequently a combination of energy-
efficiency, energy conservation, and carbon emissions reduction measures. In the case of
Portugal, according to Ferreira et al. [5], the housing stock built in the 1990s can move
to a nearly zero-energy building scenario without major difficulties, considering the
introduction of renewables on buildings that meet the cost-optimal levels. However, in
the case of old buildings, traditional building materials and architectural features limit the
range of available solutions. The most effective energy-renovation solution is frequently
a combination of the best strategies that lead to a cost-optimal solution. Therefore, for
each building, there is the need to identify the best solutions within the possible actions
(envelope; passive strategies; equipment, renewable energy systems). The diversity of
traditional construction systems found in Portuguese architecture makes necessary to
understand the real performance of this type of buildings. With this information is
3
possible to perceive how they can be improved to meet the new requirements of energy
and thermal performances, and optimize the renovation operation.
In this sense, this paper aims at contributing to the research field by presenting the
preliminary results of the study of thermal performance and comfort priorities in a set
of building case studies located in the Ovar municipality. The study included in-situ
measurements of hygrothermal parameters and surveys on occupant thermal sensation.
2. Geography, climate, and architecture in Ovar
Ovar is a small town located in the district of Aveiro, in the centre region of Portugal.
Once a fishing and salt port [6], [7], the town lost this function due to the progressive
retreat of the sea line during centuries and is now at approximately 4,5 km far from the
coastline. The town is implanted in a flat area with a valley and is divided by a small
river, formed by the confluence of two brooks that flow into the Aveiro Estuary.
Ovar has a sprawled urban mesh characterised by buildings mainly with 1 or 2 floors.
Presently, there are several buildings from the 19th and beginning of the 20th centuries, as
the case studies presented in this paper. This bourgeoisie architecture has normally
symmetrical facades design with a high front door in the center. The period of construction
reflects the preferences at the time, in a moment of return of Portuguese entrepreneur from
Brazil (as the case of Costa’s house with a characteristic platband), but also a crescent
capacity of builders through the implementation of railway which brought the opportunity
of more accessible construction materials, as the granite applied on the facades.
The town is implanted on sandy soil. However, the soils from nearby areas at East are not
only very fertile but characterized by the presence of gravel, phyllite, and schists associated
to luvisols (i.e. soils that are rich in clay) [8]. In the absence of proper stone for building
conventional masonry [6], local population had to use the locally-available resources as
building materials. Soil’s features determined the materials and the building’s systems
used. Thus, the most widespread materials/building systems in Ovar’s architecture are
walls built with adobe or with a mix of small stones (or gravel) with clay (Fig. 1).
The climate of Ovar is influenced by the proximity to the Atlantic Ocean. The region
has a temperate climate, sub-type Csb according to Köppen climate classification,
characterised by rainy winters and dry or temperate summers [9]. The annual average
mean air temperature is of 15ºC, being of 12,5ºC in Winter and of 20ºC in Summer [9].
Regarding precipitation, the annual average number of days with precipitation ≥ 1 mm
is of 125, while the annual average total rainfall is of 1000 mm, being December the
month with the highest values and July the driest month [9].
Figure 1. Materials used in Ovar’s constructions. (left) mix of stone gravel and clay
wall; (right) adobe wall.
4
3. Methodology
The methodology adopted in this study aims to understand the thermal performance and
comfort of dwellings with the same typology, built with the same building materials
and in the same climatic zone, and establish a relation between occupant’s perception
and expectation regarding their comfort. To assess indoor thermal performance and
comfort conditions of the case studies, in-situ assessments were divided into short and
long-term monitoring. The short-term monitoring was carried out at least one time per
season of the year and consisted of objective and subjective measurements. The
objective measurements were performed with the purpose of quantitatively assess the
thermal conditions within a specific room using a thermal microclimate instrument
(model Delta OHM 32.1), in compliance with standards ISO 7726 [10] and ISO 7730
[11]. The location of the equipment is chosen according to occupants’ distribution in
the room. This data is used in the analysis of the thermal comfort conditions to
determine the operative temperature, namely in the adaptive model of thermal comfort,
as explained below. Simultaneously, were carried the subjective measurements, i.e.,
evaluate environment conditions by surveying the occupants. The survey allows to
assess occupants’ satisfaction according to ASHRAE thermal sensation scale and was
based on the “Thermal Environment Survey” from ASHRAE standard 55 [12]. The
surveys were carried for the rooms that occupants considered more comfortable and/or
where they spend more time. The long-term monitoring was aimed at understanding the
fluctuations of air temperature and relative humidity profiles, indoors and outdoors,
throughout the various seasons in compliance with specified procedures and standards
[10]–[12]. For this purpose, thermo-hygrometer sensors were installed outdoors and
indoors, set to record data at 30 min intervals. During these measurements, occupants
fulfilled an occupancy table where they recorded how they had used the building, i.e.,
if they used heating or cooling systems, promoted ventilation, etc.
Thermal comfort conditions were evaluated considering an adaptive model of thermal
comfort, the most adequate for naturally conditioned areas. In order to be more
representative of the Portuguese reality, the chosen model was the one developed in the
National Laboratory of Civil Engineering (LNEC) by Matias [13]. In this model, thermal
comfort is only verified when a person feels neutral and simultaneously shows preference
to keep that neutrality. The thermal environment condition point is determined using a chart
that correlates Operative temperature (Θo) with Outdoor running mean temperature (Θrm).
4. Thermal performance study and comfort conditions assessment
4.1 Description of the case studies
4.1.1 Case study 1 – Costa’s house
Case study 1 is on the East side of the town. The building is integrated into the urban
mesh, in a group of buildings forming a small public square. Its facades are facing north,
west (street) and east (courtyard). The gross floor area is approximately 250 square meters
divided into two storeys. In the ground floor, there are the living room, the garage and
storage rooms. In the first floor, at West are the bedrooms and at East the dining room
and the kitchen (Fig. 2). It was not possible to determine exactly the date of construction
but, according to the owners, it is probably from the 19th century. Regarding the building
systems, it was not possible to determine the materials used in the building. Nevertheless,
5
it is highly probable that the materials used are the most common in this type of buildings
in Ovar, as above mentioned. Thus, the building envelope consists of walls built with a
mix of small stones and clay (average thickness of 60cm), with a pitched roof, wooden
doors and wooden framed single glazed windows in the main façade and aluminium
framed double glazed windows in the rear facade. Indoors, the partitions walls are in
tabique – a wooden framed structure where the spaces between studs are fulfilled with
small stones, bricks or clay.
Figure 2. (left) External view; (right) Floor plans showing the position of measuring
instruments (1—living room; 2—bedroom; 3—dining room; 4—kitchen).
4.1.2 Case study 2 – Begasse’s house
Case study 2 is on the West side of the town. The building is a detached house and its
facades are facing north (courtyard), south (street), west and east. The gross floor area
is approximately 230 square meters divided into two storeys. On the ground floor are
the living room, technical room and the storage room. On the first floor, at south are the
main bedrooms and at north the kitchen (Fig. 3). It was not possible to determine the
date of construction but, according to the owners, it is probably from the 20th century.
The building envelope consists of walls built with a mix of small stones and clay
(average thickness of 65cm), with a pitched roof, wooden doors and wooden framed
single glazed windows. Indoors, the partitions walls are in tabique.
Figure 3. (left) External view; (right) Floor plans showing the position of measuring
instruments (1—living room; 2—bedroom 2; 3—bedroom1; 4—kitchen; 5—
bedroom3).
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4.2 Hygrothermal monitoring and comfort assessment
The thermal performance monitoring was carried out for all seasons of the year.
However, in this paper, only the results obtained for the two most demanding seasons
in what thermal comfort is concerned, i.e., winter and summer, are addressed and
discussed. The summer monitoring was conducted over the period from 21st June to
19th September 2016 and the winter monitoring over the period from 21st December to
3rd February 2017.
4.2.1 Summer monitoring
From the analysis of the results, it is possible to verify that during summer, outdoor mean
air temperature was of about 21°C. The maximum air temperature was around 25°C in
most of the days, surpassing 30ºC in some days. Minimum air temperature during the
monitoring period was of about 14ºC. Outdoor mean relative humidity was around 70%
while maximum and minimum values were around 90 and 30%, respectively.
In case study 1, indoor rooms showed a stable air temperature profile (Fig. 4). During
all the monitoring period, the mean air temperature in indoor rooms was around 22-
24°C. In the bedroom, the maximum air temperature was higher than in other rooms,
probably due to solar exposure of the main facade (west) and also by the higher heat
transfer coefficient of the single-glazed windows. In opposition, the living room had a
maximum air temperature between 3-5ºC lower than the other monitored rooms (Fig.
4). The high thermal inertia of walls and floor and the fact that it has less glazed area,
is probably the reason for the milder temperature profile when compared with the
remaining upper floor rooms. In case study 2, indoor monitoring results show that all the
inhabited rooms have a stable temperature profile, with mean values around 22-23ºC (Fig.
4), and maximum and minimum temperatures within thermal comfort range values most
of the time. The living room had the most stable profile with higher minimum temperature
(20.4ºC) and lower maximum temperature (25ºC). Its position on the ground floor,
partially buried, and the high mass walls allow stabilizing the temperature. In both cases
studies, beyond the thermal inertia, all the indoor rooms are naturally ventilated during
the morning, what contributes for removing heat loads and cool the house.
Regarding the relative humidity (Fig. 5), for both case studies, the indoor mean values
recorded are high and between 60-70% for all rooms, above of what it is recommended
(between 40-60% [14]). The profiles are stable with slight daily variations in some
rooms, probably due to the opening of windows and doors for ventilation. During the
days with lower outdoor relative humidity, indoor values were higher. This is certainly
due to the hygroscopic inertia of the walls, made of earthen materials.
The assessment of the summer season comfort conditions was done in case study 1 for
the kitchen/dining room and in case study 2 for the living room (Fig. 6). In both cases,
from the analysis of the charts, it was found that the rooms had a comfortable thermal
environment, within the comfort range but close to the lower limit. In the subjective
assessment carried out, two occupants showed to be “neutral” (comfortable) and one as
“slightly cool” in the thermal sensation scale, confirming the objective measurements.
Although the results from the short-term measurements represent one day, the
conditions of thermal comfort can be extrapolated to almost all days, since there is a
strong relation of dependency between the air temperature and the operative
temperature [13].
7
Figure 4. Indoor and outdoor air temperature profiles during summer season. (left)
Case Study 1; (right) Case Study 2.
Figure 5. Indoor and outdoor relative humidity profiles during summer season. (left)
Case Study 1; (right) Case Study 2.
Figure 6. Adaptive comfort chart for summer monitoring without heating/cooling
systems. (left) Case study 1 – Thermal comfort temperature (operative temperature) in
the dining room/kitchen; (right) Case study 2 – Thermal comfort temperature
(operative temperature) in the living room.
4.2.2 Winter monitoring
During the monitoring, outdoor mean air temperature was of about 9°C. The maximum
air temperature was around 17°C but in most of the days was around 12-13ºC. The
minimum air temperature during the monitoring period was of 0ºC. Outdoor mean
relative humidity was around 85% while maximum and minimum values were around
100 and 47%, respectively.
In case study 1, indoor rooms showed air temperature profiles below 18ºC during the
monitoring (Fig. 7), with mean values between 12-14ºC. Maximum air temperature in
dining room/kitchen and bedroom was around 18-19ºC. The relative stability in these
rooms was due to the thermal inertia but also to the use of portable electric heaters that
8
were frequently switched on during the monitoring. In case study 2, the indoor
temperature profiles (Fig. 7) show significant variations in regular periods of time. These
variations and temperature peaks are due to the occupation profile, i.e, the house is
permanently occupied mainly three days per week, and in those days temperature rises
very rapidly when the central heating system is activated. When the heating system is
turned off, air temperature decreases slowly through the following days until “stabilizes”
around maximum outdoor temperature values, however, low. In this case, the use of the
central heating system (boiler + radiators) allowed maintaining indoor temperature within
comfort range values. However, in case study 1, is possible to see that the type of heating
system used was not enough to ensure comfort conditions in most of the days.
Considering the relative humidity, for both cases indoor spaces had relatively stable
profiles with mean values between 60-70% (Fig. 8). In case study 2, when the heating
system is activated, values decreased and stabilized between 40-60%, a boundary that
is adequate for human health. In this case, the living room has the lower values, but this
is due to the use of a dehumidifier device. Although the values recorded for both cases
are high for a healthy indoor environment, are stable and considerably lower than those
recorded outdoors. It is also possible to verify that the mean values between the two
seasons are very similar. Climatic factors, namely the influence of the ocean, is a strong
reason for frequent high relative humidity values.
Figure 7. Indoor and outdoor air temperature profiles during winter season. (left) Case
Study 1; (right) Case Study 2.
Figure 8. Indoor and outdoor relative humidity profiles during winter season. (left)
Case Study 1; (right) Case Study 2.
The assessment of the winter season comfort conditions was done in case study 1 was
done in case study 1 for the kitchen/dining room and in case study 2 for the living room
(Fig. 9). In case study 1, the kitchen/dining room had a thermal environment in the
lower limit of the comfort range, even with heating equipment turned on. In the
subjective assessment, three occupants answered as being “neutral” (comfortable) and
two as “slightly warm”. Although the objective measurements show that room’s
environment is in the lower limit of the comfort range, two occupants answered as being
9
“slightly warm”, in the opposite limit. The explanation for this result is that these
occupants were the ones closest to the electric heater. In case study 2, with the heating
system activated, the living room had a good thermal environment (Fig. 9). In the
subjective assessment, two occupants answered as being “slightly warm”, one as being
“hot” and one as being “slightly cool” in the thermal sensation scale. Although the
objective measurements showed that the room had a good thermal environment, almost
in the middle of the comfort range, none of the occupants answered as being
comfortable. This result has several explanations. The first is the thermal resistance of
clothes, the second is that one occupant was closest to the heat radiator and the other
was the closest to the external wall, being the two influenced by the radiation effect,
one receiving heat from the radiator and the other losing heat to the cool wall. The
measurements in the two cases reflect the complexity of assessing thermal comfort and
the importance of choosing an adequate point for performing the measurements, they also
show the difference between occupants and the need to perform longer measurements in
order to force occupants to adapt their clothes to the environment they are in.
Figure 9. Adaptive comfort chart for winter monitoring with heating system. (left) Case
study 1 – Thermal comfort temperature (operative temperature) in the dining
room/kitchen; (right) Case study 2 – Thermal comfort temperature (operative
temperature) in the living room.
5. Conclusions
The preliminary results of the thermal environment monitoring carried out in the two
case studies, support that was possible to achieve indoor thermal comfort during cooling
season by passive means alone. During winter, in both case studies, indoor thermal
conditions were below the comfort range and the periods of thermal discomfort had to
be overcome by using heating systems. It was observed that indoor temperature and
relative humidity profiles were relatively stable in both seasons. The thermal and
hygroscopic inertia of the envelope, mainly schist+clay and adobe walls with thickness
between 0.50-0.65cm, has a positive influence in this behaviour. An example is case
study 2, where after turning off the heating system, air temperature takes about a week
to decrease to the previous levels. The surveys on occupants’ thermal comfort
corroborated the objective assessments, although with some discrepancies in winter
assessment. It should be noted occupants’ action in the regulation of their comfort
conditions (e.g., promotion of morning ventilation during the summer period).
Therefore, this is an on-going research work that intends to collect more detailed data
of a set of 4 case studies, in order to understand their thermal performance and identify
energy-efficiency renovation solutions that can improve comfort conditions.
10
Acknowledgments
The authors would like to acknowledge the support granted by the Portuguese
Foundation for Science and Technology (FCT), in the scope of the Doctoral Program
Eco-Construction and Rehabilitation (EcoCoRe), to the Ph.D. scholarship with the
reference PD/BD/113641/2015 and to postdoctoral support with the reference
SFRH/BPD/113053/2015, that were fundamental for the development of this study.
The authors also wish to thank the owners of case study buildings, Mr. Costa and Mr
Begasse, for helping and supporting this research work.
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