Analysis of thermal comfort in nursing homes in the cross-border cooperation area of Spain - Portugal
1. Introduction
According to the United Nations (2017), life expectancy in recent years has increased, thus increasing the number of older people. In 2017, there were an estimated 962 million people aged 60 or over in the world, representing 13% of the world's population. The population aged 60 or over is growing at a rate of about 3 per cent per year. Currently, Europe has the largest percentage of the population aged 60 or over (25%). The number of people aged 80 and over is also expected to triple by 2050, and by 2100 it will increase to almost seven times its value by 2017.
This trend explains the growing demand for long-term care services (Damiani et al., 2009), such as Elderly Care Centres (ECCs). In addition, considering that people over 65 spend a considerable part of their lives indoors, energy consumption to maintain the indoor conditions of these centers is high (Mendes et al., 2015). Clearly, the thermal comfort of these centres cannot be ignored.
Determining the parameters influencing thermal comfort is necessary both to design pleasant spaces and to ensure the well-being and health of building occupants. Good design and management of constructed buildings not only provides a comfortable thermal sensation for the occupants, but also determines the amount of energy that the building's cooling and heating systems will consume. In the current context of climate change and global warming, the inclusion of the concept of adaptive thermal comfort in thermal comfort standards makes it possible to adopt new efficiency and energy-saving strategies and consistently meet the requirements of sustainable development.
Both the international standards ISO 7730:2005, ASHRAE Standard 55:2013 and EN 15251:2007 aim to specify the environmental conditions recommended for a middle-aged population.
Field studies show that current existing standards cannot be applicable to older people because their thermal responses are different. This segment of the population has very specific characteristics such as lower levels of activity, not being able to easily change their level of activity or clothing, lack of vasoconstriction that can decrease wind chill, or more tolerance to heat that can cause dehydration in summer.
The aim of this project is to analyse the thermal comfort of elderly people in Nursing Homes located in different climatic zones of cross-border cooperation space in Spain-Portugal and to predict which thermal conditions are acceptable or preferred for this group of people.
To this end, the environmental parameters (air temperature, average radiant temperature, air speed and air humidity), outdoor conditions (temperature and relative humidity), physical activity, clothing and thermal sensation of the residents of various nursing homes located in Mediterranean and Atlantic climates will be analysed.
In order to improve the ageing and quality of life of citizens in the cross-border area of the Spanish-Portuguese Cooperation Area, this project aims to determine the parameters influencing thermal comfort for elderly people, bearing in mind that two different climates coexist in the cross-border area: the Atlantic climate and the Mediterranean continental climate. Comfort conditions can vary substantially depending on the climate. It is therefore of great interest to analyse the different models of thermal comfort under different climatic conditions. The multidisciplinary team (Spain and Portugal) will make it possible to evaluate the different climatic zones, compare them and determine their specific characteristics.
5 ECCs will be selected in the Porto metropolitan area (Atlantic climate) and 5 ECCs in the border area between Spain and Portugal (Mediterranean continental climate) and a longitudinal analysis will be carried out over several seasons in the common areas of the ECCs. In parallel, residents will be surveyed once a week to determine their wind chill within the Ashrae scale. These data will be used to analyse the factors influencing thermal comfort for older people and to develop analytical models to determine the thermal well-being characteristics for this group of people within the different climatic zones.
The application of adaptive comfort models for older people offers the possibility of improving their quality of life and at the same time offers great potential for energy savings. This saving translates into approximately 30% of the cooling load, compared to a fixed temperature setpoint as indicated by conventional comfort theory.
The application of environmental comfort models for elderly people offers the possibility to improve their quality of life and at the same time can offer additional energy savings. That is why, from the analytical model obtained will be compared with historical environmental data from the same centers to, on the one hand, create good practices that improve the quality of life of people, and on the other hand objectify the energy efficiency of residential centers.
2. Evaluation of thermal comfort
Thermal comfort can be described as the characteristics of the environment that affect the exchange of heat between the human body and the environment (Ashrae 2013). Thermal comfort depends on both physical and physiological parameters and is affected by clothing, activity, age, health status, sex, and adaptation to the individual's and space's climate and local environment (Vandentorren et al., 2006).
When it comes to evaluating thermal comfort, there are two main models that can be used: the medium-voting predicted model (PMV) and the adaptive model.
2.1. Planned average voting model (MVP)
The most commonly used model for assessing overall or body thermal comfort is Fanger's (1973) model of the predicted average vote (PMV). According to this model, in order for a given situation to be considered thermally comfortable, it must be fulfilled, as a basic condition, that allows the physiological mechanisms responsible for thermoregulation to reach thermal equilibrium; that is, that the body is capable of balancing the heat gained (of metabolic origin or coming from the environment) and the heat eliminated by means of different procedures.
However, achieving thermal equilibrium does not guarantee comfort. The Fanger method considers the level of activity (met), the characteristics of clothes (clo), the dry temperature (Ta), the relative humidity (HR), the average radiant temperature (Trd) and the air speed (va). All these variables influence the thermal exchanges between man and environment, affecting the sensation of comfort.
PMV is expressed on the Ashrae scale of 7 thermal sensation points (cold, cool, slightly cold, neutral, slightly hot, hot). The result of the model is a hypothetical voting thermal sensation for an average person: that is, the average response of many people with equal dress and activity levels, who are exposed to identical and uniform environmental conditions. Ashrae (2013) defines wind chill as a conscious feeling, which requires subjective evaluation. The PMV model is adopted by the international standards ISO 7730 (2005), Ashrae Standard 55 (2013) and EN 15251 (2007). These standards aim at specifying the comfort conditions of middle-aged people inside the building. EN 15251 (2007) mentions that, for spaces occupied by very sensitive and fragile people, PMV should be kept between -0.2 and +0.2 on the Ashrae 7-point thermal scale. EN 15251 (2007) includes three categories (I, II and III) and indicates that the most restrictive category should be adopted for older occupants, while Ashrae 55 (2013) has only 2 ranges (80% or 90% of satisfied people) and no specific indication for older people.
Fanger's PMV model is widely used and accepted in the field of thermal comfort assessment. However, it is a stationary model (static model) and therefore does not take into account temperature variations throughout the day, is the result of research into thermal chambers, is only applicable to humans exposed to a long period in constant conditions and with a constant metabolic rate and does not consider the adaptation of occupants to achieve comfort conditions (Fanger 1973).
These reasons have led to the existence in the research community of authors who doubt the predictive capacity of the PMV model in real buildings, even considering other models.
Adaptive model of thermal comfort
The adaptive criterion is the result of field studies whose purpose was to analyze the real acceptability of thermal environments, which depends closely on the context, the behavior of the occupants and their expectations.
In contrast to the static model of thermal comfort, in the adaptive model people play an instrumental role by creating their own thermal preferences through the way they interact with the environment, modify their own behaviour or gradually adapt their expectations according to the thermal environment in which they find themselves (Brager & de Dear, 1998). A generic definition of the term adaptation could be a gradual decrease in the body's response to repeated stimulation from the environment.
From this general definition it is possible to clearly distinguish three categories of thermal adaptation (Brager & de Dear, 1998):
- Adjustment of behaviour: These are adjustments of activity, putting on and taking off clothes, regulating air conditioning, taking a nap on a hot day, etc.
- Physiological adaptation: Changes in psychological response as a result of exposure to environmental thermal factors. This may lead to a gradual decrease in the stress produced by this exposure. However, these processes occur with prolonged exposure to extreme conditions. Therefore, their influence on building is not very significant.
- Psychological adaptation: The altered perception and subsequent reaction to sensory information due to past experiences and expectations.
In recent years, many authors have added field studies to laboratory studies with the aim of obtaining more real information about comfort in workplaces. Field studies also allow the analysis of other factors that cannot be simulated in thermal chambers, such as the response of individuals in their daily habits, daily clothing and behavior without the existence of any type of restriction (de Dear et al. 1998). The subjectivity of thermal experience and the interpretative flow of complex interactions between occupants and their environment have been the focus of a number of studies and provide the theoretical underpinnings of studies on thermal comfort from an adaptive point of view.
De Dear et al. (1998) concluded that there is a tendency for the thermal neutrality temperature to increase as the outside temperature increases. This increase is much greater in naturally ventilated buildings. Many authors explain this increase in temperature neutrality partly as an adaptive response to users' behaviour by increasing their level of clothing. However, as they themselves demonstrate, this increase would only explain a percentage of this deviation. The rest of the deviation is justified by a process of psychological adaptation derived from the level of expectation. Thus, our thermal experience subconsciously indicates that, in exterior or interior spaces with a notable relationship with the exterior, the environment suffers frequent thermal variations (from Dear et al. 1998).
Ashrae Standard 55 (2013) and EN 15251 (2007) include adaptive thermal comfort models. Ashrae's adaptive standard only applies to buildings without installed mechanical cooling, while EN15251 can be applied to mixed mode buildings as long as the system is not in operation.
Nicol and Humphreys have led research on adaptive comfort models and have proposed various models for types of buildings with and without ventilation (Humphreys M & Nicol F; 2017; Nicol F & Humphreys M (2010); Rijal, Humphreys & Nicol 2017; 2009).
3. Thermal comfort in the elderly
Given the rapid increase in population ageing in recent years, it is important to address the thermal comfort of this group of people (Hoof et al., 2017; Yang et al., 2016; Alves et al., 2016; Hong et al., 2015; Tweed et al., 2015; Mendes et al., 2013; Mendes et al., 2015; Hwang and Chen, 2010; Schellen et al., 2010; Hoof et al., 2010).
Although Ashrae suggested that the thermal sensation of older people and younger adults does not differ, and that the effects of sex and age are due to activity and clothing, several studies have indicated that the optimal thermal sensation of older people differs from that of younger adults (Jiao et al., 2017; Schellen et al., 2010; Hwang and Chen, 2010; DeGroot, 2007; Hoof, 2006) and the sensitivity of the two populations to cold and hot environments may vary. The biological aging process may affect the perception of thermal comfort due to a decrease in the ability to regulate body temperature with age. On average, older adults require higher environmental temperatures (Hong et al., 2015; Tweed et al., 2015; Hwang and Chen, 2010; Schellen et al., 2010; Hoof et al., 2010).
In general, the elderly appear to perceive thermal comfort differently from the young due to a combination of physical and behavioral aging differences (Hoof et al., 2010; Hoof and Hensen, 2006). On average, older adults have a lower level of activity, and therefore a lower metabolic rate, than younger adults, the main reason why they require higher ambient temperatures (Hwang and Chen, 2010). The elderly have reduced (i) muscle, (ii) work capacity, (iii) sweat capacity, (iv) ability to transport heat from the body to the skin, (v) hydration levels, (vi) vascular reactivity, and (vii) cardiovascular stability. Tsuzuki and Ohfuku (2002) also found that adults have reduced sensitivity to heat in cold seasons. The ability to regulate body temperature tends to decrease with age and there is a reduction in sweating activity in older people compared to younger age groups (Hoof and Hensen, 2006). These differences are even more pronounced in older women. Tsuzuki and Iwata (2002) found that water loss from evaporation does not increase significantly with metabolic rate in older adults who exercise lightly. According to Hwang and Chen (2010), physiologically older adults prefer about 2oC more than younger people. Several studies (Hoof and Hensen, 2010; Hwang and Chen, 2010; Guedes et al., 2009; Raymann and Van Someren, 2008; Schellen et al., 2010) also corroborate that psychologically they also prefer warmer environments and that the 20-24°C comfort zone is not warm enough for this population group. The optimal temperature would be around 25.3oC for sedentary elderly people. On the other hand, operational temperature measurements (what people experience thermally in a space) in Portuguese nursing homes (Guedes et al., 2009) ranged from 16oC to 25oC in winter and 22oC to 31oC in summer.
On the other hand, several studies in homes inhabited by the elderly have associated thermal comfort with cardiac mortality due to low temperatures in isolated homes (Raymann and Van Someren, 2008; Bokenes et al., 2011). In addition, the European project PHEWE (Analitis et al., 2008) reported a significant short-term increase in cardiovascular mortality of 1.72% in association with a 1°C drop in an average temperature of 15 days (Lanzinger et al., 2014). In addition, it also concluded that there is an elevated short-term risk of myocardial infarction with a 10°C decrease in air temperature associated with cold temperatures (Wolf et al., 2009). Susceptible groups should be at a minimum temperature of 20°C to avoid cardiovascular problems (Ormandy and Ezratty, 2012). In this sense, the thermal environment in residences generally does not produce serious diseases; however, this factor can have a significant impact on the general well-being and daily comfort of its residents. A poor thermal environment also aggravates the influence of air pollutants on occupants' health (Mendes and Teixeira, 2014). The standards mentioned above are mainly based in offices, where users are between 20 and 65 years of age approximately. Most people in ECC are over 65.
Recently the research team of Mendes et al. (2017) found that the quality of life of older people is related to their thermal comfort in the winter season. In this study, PMV values above -0.7 had a quality of life (QoL) coefficient of 11.13 units compared to PMV values below -0.7. These findings are relevant to public health and can be useful in understanding which variables in living areas have an impact on quality of life and consequently be able to implement preventive policies in relation to standards and guidelines for this susceptible population group.
On the other hand, the GRIC research team (UPC) carried out an analysis in the residential centre of Sanitas Mayores Les Corts (Barcelona). There the interior conditions in different areas of the ECC were analysed and the degree of thermal comfort of the residents was evaluated by means of a survey (Gelabert, 2016, Pujol 2017, Molina 2017). This first study concluded that all those surveyed felt comfortable with warmer environments than those foreseen in the current models (Gelabert, 2016, Pujol 2017, Molina 2017). It was concluded that the standard 21-23oC for winter and 25-27oC for the comfort zone during summer may not be warm enough for older adults, who reported an optimal temperature above 25oC in all seasons.
These studies highlight the need for specific comfort models for older adults. In general, comfort standards do not currently apply to the elderly population. They only set higher restricted PPD limits, rather than determining the conditions that affect thermal comfort.
References
Alves C.A., Duarte D.H., Gonçalves F.L. (2016), Residential buildings' thermal performance and comfort for the elderly under climate changes context in the city of São Paulo, Brazil Energy Build., 114, 62–71.
Analitis A, Katsouyanni K, Biggeri A, Baccini M, Forsberg B, Bisanti L, Kirchmayer U, Ballester F, Cadum E, Goodman PG, Hojs A,Sunyer J, Tiittanen P, Michelozzi P (2008) Effects of cold weather on mortality: results from 15 European cities within the PHEWE project. Am J Epidemiol 168(12):1397–1408.
ASHRAE Standard 55-2013: Thermal Environmental Conditions for Human Occupancy, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Atlanta, 2013.
Bøkenes L., Mercer J.B., MacEvilly S., Andrews, J. F., and Bolle, R. (2009). Annual variations in indoor climate in the homes of elderly persons living in Dublin, Ireland and Tromsø, Norway. Eur. J. Public Health 21: 526–531
Brager, G.S. & de Dear, R.J., 1998. Thermal adaptation in the built environment: a literature review. Energy and buildings, 27(1) 83–96.
de Dear, R. et al., 1998. Developing an Adaptive Model of Thermal Comfort and Preference. ASHRAE Transactions, 104(March), pp.145-167.
EN 15251:2007: Indoor environmental input parameters for design and assessment of energy performance of buildings- addressing indoor air quality, thermal environment, lighting and acoustics. CEN, Brussels.
Fanger, P.O., (1973). Assessment of man’s thermal comfort in practice. British journal of industrial medicine, 30(4), 313-24.
Gelabert, D (2016) Estudio para el desarrollo de un conjunto de indicadores para la caracterización del confort de los usuarios de los edificios de Sanitas Mayores. Trabajo Final de Grado, ESEIAAT, UPC.
Guedes, M.C., Matias, L & Santos, C.P, (2009) Thermal comfort criteria and building design: Field work in Portugal," Renewable Energy, 34(11), pages 2357-2361.
Hoof J., Schellen L. Soebarto J, Wong J and Kazak (2017) Ten questions concerning thermal comfort and ageing, Building and Environment 120 (2017) 123-133.
Hoof J., Kort H.S.M., Hensen J.L.M., Duijnstee M.S.H., Rutten P.G.S. (2010) Thermal comfort and the integrated design of homes for older people with dementia Build. Environ., 45 (2) 358–370.
Hoof, J. Hensen J.L.M. (2006) Thermal comfort and older adults. Gerentchnology 4(4).
Hong L, Yuxin W, Heng Z, Xiuyuan D. (2015), Field study on elderly people's adaptive thermal comfort evaluation in naturally ventilated residential buildings in summer Heat. Vent. Air Cond., 6 015.
Huang C, Barnett AG, Wang X, Tong S. (2012) Effects of extreme temperatures on years of life lost for cardiovascular deaths: a time series study in Brisbane, Australia.
Humphreys M & Nicol F (2017) Towards an adaptive model for thermal comfort in Japanese offices Building Research and Information, v 45, n 7, p 717-729, October 3, 2017
Hwang, R.L., Chen, C.P., (2010). Field study on behaviors and adaptation of elderly people and their thermal comfort requirements in residential environments. Indoor Air 20 (3), 235–245.
ISO 14415:2005: Ergonomics of the thermal environment - Application of International Standards to people with special requirements.
ISO 8996:2004: Ergonomics of the Thermal Environment determination of Metabolic Heat Production.
Jiao, Y, Yu, H. Wang, Z. Wei, Q. Yu, Y. (2017) Influence of individual factors on thermal satisfaction of the elderly in free running environments, Build. Environ. 116 218:227.
Lanzinger, S., Hampel, R., Breitner, S., Ruckerl, R., Kraus, U., Cyrys, J., Geruschkat, U., Peters, A., and Schneider, A. (2014) Short-term effects of air temperature on blood pressure and pulse pressure in potentially susceptible individuals. Int. J. Hyg. Environ. Health 217: 775– 784
Mendes, A., A. L. Papoila, P. Carreiro-Martins, L. Aguiar, S. Bonassi, I. Caires, T. Palmeiro, A. S. Ribeiro, P. Neves, C. Pereira, A. Botelho, N. Neuparth, and J. P. Teixeira. 2017. "The influence of thermal comfort on the quality of life of nursing home residents." J Toxicol Environ Health A:1-11. doi: 10.1080/15287394.2017.1286929.
Mendes A, Pereira C, Mendes D, Aguiar L, Neves P, Silva S, Batterman S, Teixeira J.P. (2013), Indoor air quality and thermal comfort—results of a pilot study in elderly care centers in Portugal J. Toxicol. Environ. Health, Part A, 76 (4–5), 333–344.
Mendes, A, Bonassi, S, Aguiar, L, Pereira, C, Neves, P, Silva, S, Mendes, D, Guimaraes, L, Moroni, P, Teixeira, J.P, (2015) Indoor air quality and thermal comfort in elderly care centers, Urban Clim. 14 486:501.
Mendes, A., and Teixeira, J. P. (2014). Sick building syndrome. Encyclopedia of Toxicology, 3rd edition, vol 4., edited by P. Wexler, 256–260. Elsevier Inc. Academic Press, the Netherlands.
Molina, M. (2017) Estudio sobre las condiciones de confort en edificios de residencias para personas mayores. Trabajo Final de Grado, ESEIAAT, UPC.
Naciones Unidas, (2017), Department of Economic and Social Affairs Population Division. World Population Prospects: The 2017 Revision, Key Findings and Advance Tables.
Nicol F & Humphreys M (2010) Derivation of the adaptive equations for thermal comfort in free-running buildings in European standard EN15251 Build. Environ., 45 (1) 11-17.
Ormandy, D., and Ezratty, V. (2012). Health and thermal comfort: From WHO guidance to housing strategies. Energy Policy, 49: 116–121.
Rijal H.B. Humphreys M & Nicol F (2009) Understanding occupant behaviour: the use of controls in mixed-mode office buildings Building Research & Information, v 37, n 4, p 381- 96, July 2009
Rijal H.B. Humphreys M & Nicol F (2017) Towards an adaptive model for thermal comfort in Japanese offices Building Research & Information, v 45, n 7, p 717-29, 2017
Pujol, J. (2017) Estudio sobre la implantación de mejoras de eficiencia energética de las instalaciones de climatización y ventilación de uno de los edificios de Sanitas Mayores y su adecuación al confort de sus residentes. Trabajo Final de Máster ESEIAAT, UPC.
Raymann, R., and Van Someren, E. (2008) Diminished capability to recognize the optimal temperature for sleep initiation may contribute to poor sleep in elderly people. Sleep 31: 1301– 1309. Schellen, L, van Marken Lichtenbelt W.D, Loomans, M.G.L.C. Toftum, J, De Wit M.H. (2010), Differences between young adults and elderly in thermal comfort, productivity, and termal physiology in response to a moderate temperature drift and a steady-state condition, Indoor air 20 (4) 273:283.
Tsuzuki, K., and Iwata, T. (2002). Thermal comfort and thermoregulation for elderly people taking light exercise. Proceedings of Indoor Air 02, edited by H Levin, 647–652. Monterey, CA, USA. Tweed C, Humes N, Zapata-Lancaster G (2015), The changing landscape of thermal experience and warmth in older people's dwellings Energy Policy, 84, 223–232.
UNE-EN ISO 7730:2005: Ergonomía del ambiente térmico. Determinación analítica e interpretación del bienestar térmico mediante el cálculo de los índices PMV y PPD y los criterios de bienestar térmico local.
Yang J, Nam I, Sohn J.R. (2016), The influence of seasonal characteristics in elderly thermal comfort in Korea Energy Build., 128 583–591.
Vandentorren S, Bretin P, Zeghnoun A, Mandereau-Bruno L, Croisier A, Cochet C, Riberon J, Siberan I, Declercq B, Ledrans M, (2006), August 2003 heat wave in France: risk factors for death of elderly people living at home. Eur. J. Public Health 16, 583–591.
Wolf, K., Schneider, A., Breitner, S., von Klot, S., Meisinger, C., Cyrys, J., Hymer, H., wichmann, H. E., Peters, A. and Cooperative Health Research in the Region of Ausburg Study Group. (2009). Air temperature and the occurrence of myocardial infarction in Augsburg, Germany. Circulation 120: 735–742.
