A framework for adopting adaptive thermal comfort principles in design and operation of buildings

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A Framework for Adopting Adaptive Thermal Comfort Principles in Design and Operation of Buildings Runa T. Hellwig , Despoina Teli , Marcel Schweiker , Joon-Ho Choi , M.C. Jeffrey Lee , Rodrigo Mora , Rajan Rawal , Zhaojun Wang , Farah Al-Atrash PII: DOI: Reference:

S0378-7788(19)31616-0 https://doi.org/10.1016/j.enbuild.2019.109476 ENB 109476

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Energy & Buildings

Received date: Revised date: Accepted date:

31 May 2019 5 September 2019 28 September 2019

Please cite this article as: Runa T. Hellwig , Despoina Teli , Marcel Schweiker , Joon-Ho Choi , M.C. Jeffrey Lee , Rodrigo Mora , Rajan Rawal , Zhaojun Wang , Farah Al-Atrash , A Framework for Adopting Adaptive Thermal Comfort Principles in Design and Operation of Buildings, Energy & Buildings (2019), doi: https://doi.org/10.1016/j.enbuild.2019.109476

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A Framework for Adopting Adaptive Thermal Comfort Principles in Design and Operation of Buildings Runa T. Hellwig1,*, Despoina Teli2, Marcel Schweiker3, Joon-Ho Choi4, M.C. Jeffrey Lee5, Rodrigo Mora6, Rajan Rawal7, Zhaojun Wang8, Farah Al-Atrash9 1 Aalborg University, Department of Architecture, Design and Media Technology CREATE, Rendsburggade 14, 9000 Aalborg, Denmark 2 Division of Building Services, Department of Architecture and Civil Engineering, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden 3 Karlsruhe Institute of Technology, Building Science Group, Englerstr. 7, 76131 Karlsruhe, Germany 4 Building Science, School of Architecture, University of Southern California, 850 West 37th St. WAH #204, Los Angeles, CA, 90089, U.S.A. 5 National Taichung University of Science and Technology, Department of Interior Design, 129, Sec. 3 Sanmin Road, 40401, Taichung, Taiwan 6 Building Science Graduate Program, British Columbia Institute of Technology (BCIT), 3700 Willingdon Avenue, Burnaby, Canada. 7 Centre for Advanced Research in Building Science and Energy, CEPT University, K.L.Campus, Navarangpura, Ahmedabad 380009, India 8 Harbin Institute of Technology, School of Architecture, Harbin, 150090, China. 9 School of Architecture and Built Environment, German Jordanian University, Darat Othman Bdeir, P.O.Box 35247, 11180, Amman, Jordan. *Corresponding author: Runa T. Hellwig, [email protected] Declarations of interest: none Abstract: The concept of adaptive thermal comfort was formulated many decades ago and has been validated in numerous field studies. As a result, wider acceptable indoor temperature ranges based on adaptive models have been included in international and national standards and the adaptive approach to thermal comfort is regarded as a significant contributor in achieving low energy building design and operation. Despite the everincreasing scientific literature on adaptive comfort around the world, the overall understanding of how to translate the adaptive principles into design practice and concepts for operating buildings is still limited, which suggests a gap between the scientific outcomes and the real-world applications. This discussion paper identifies the challenges and gaps in using the principles of adaptive thermal comfort by design practitioners and discusses them in light of relevant research findings. More than 100 literature sources were reviewed in support of the discussion. The paper then proposes a framework that aims to facilitate the adoption of adaptive comfort principles in design and operation of buildings and describes the outline of an imminent guideline for low energy building design based on the concept of adaptive thermal comfort. Keywords: adaptive thermal comfort, personal control, building energy efficiency, climate context, sufficiency

1. Introduction Establishing an acceptable sufficient indoor climate without increasing the energy use in indoor spaces is one of the world’s challenges. Buildings are often designed to maintain constant, nearly steady-state thermal conditions uniform throughout the building with the aim to minimize legal liability and maximise comfort (Deuble and de Dear 2012a). These buildings place control on automatic systems, which manage the indoor environmental conditions and deny occupants means of intervention (Bordass and Leaman 1997). In contrast, buildings designed and operated according to the adaptive thermal comfort concept inherently favour a certain indoor environmental variation, with indoor thermal conditions changing gradually in response to the prevailing outdoor conditions, while remaining within the limits that people readily adapt to. The adaptive thermal comfort concept is not new and researchers found numerous proofs of the concept in field studies (e.g. Nicol and Humphreys 1973, Auliciems 1981b, de Dear et al. 1997, McCartney and Nicol 2002, Manu et al. 2016), supporting that humans are satisfied with a wide range of indoor temperatures provided they have the opportunity and willingness to adapt by themselves. However, the overall understanding of how to design for adaptation in relation to the outdoor conditions, hence how to translate the adaptive principles into a design culture and concepts for operating buildings is still limited. Consequently, there is gap between scientific research and real-world-application, which needs to be dealt with. Therefore, Annex 69: “Strategy and practice of adaptive thermal comfort in low energy buildings” was established in 2015 by international thermal comfort experts under the umbrella of the International Energy Agency’s (IEA) Energy in Buildings and Communities Programme (EBC). Besides establishing a) a new extended database, Annex 69 has the following overall objectives: b) to provide indoor thermal environment criteria based on the adaptive concept; c) to provide a basis for the creation or revision of indoor environment standards; d) to propose passive building design strategies to achieve thermal comfort with low energy consumption and e) to provide design guidelines for new cooling and heating devices (EBC 2018). One of the major project deliverables will be a design guideline on how to use the adaptive comfort concept for lowering the energy use in buildings, including the usage of personal thermal comfort systems. This is an ongoing activity of the authors of this paper within activity B2 of the Annex. The planned guideline aims to facilitate the application of the principles of adaptive thermal comfort in planning practice. The main target groups are building planners (architects, engineers, sustainability certification consultants/councils) and building operators (facility managers, owners, tenants). The guideline can be a valuable piece of information for the discussions between building owners and occupants and their building planners and building operators. Therefore, the aim of this paper is to discuss challenges and gaps identified in using the principles of adaptive thermal comfort by building practitioners and associates. Challenges relate first of all to the understanding of the adaptive principles, whereas the gaps are mainly related to missing information and links for the practical application of the 2

adaptive concept. We relate these challenges and gaps to findings from research. We then propose a framework that aims to facilitate the adoption of adaptive comfort principles in design and operation of buildings as a complementary tool to a holistic design 1 process. Our framework will serve to outline the scope of the future guideline for low energy building design based on the concept of adaptive thermal comfort. 2. Adaptive comfort concept and its principles Human perception of the indoor thermal environment together with the notion of thermal comfort have been researched already in the beginning of the 19th century (Houghton and Yaglou, 1923a,b). The relationship between thermal perception and prevailing indoor and outdoor conditions was established by the pioneering works of Auliciems (1969a, 1969b, 1981b, 1981a), Nicol and Humphreys (1973) and Humphreys (1976, 1978). In contrast to the static view on thermal comfort, they define thermal comfort as a self-regulating system. Their work forms the foundation for the formulation of the three adaptive principles, today known as behavioural, physiological, and psychological (de Dear et al. 1997). In this context, the work by Auliciems, Humphreys and Nicol is the first to mention a) behavioural thermoregulation by changing posture or activity, clothing insulation levels or the thermal environment and b) social factors and constraints related to thermal control (Nicol and Humphreys, 1973). Thermoregulatory adjustments based on acclimatisation processes (Auliciems, 1981b) have been subject of earlier research in the thirties. Reviewing the three adaptive principles, Schweiker et al. (2012) conclude that their basic mechanisms are known, but more research is necessary for a further understanding of each adaptive principle and their interactions. To summarise these mechanisms, behavioural adaptation consists of clothing adjustments or adjustments to the indoor thermal environment by adaptive opportunities (e.g. window opening or using a fan). These adaptive behaviours affect the human body’s heat balance by regulating the rate of internal heat generation and the body heat loss via convection, long-wave radiation, evaporation or conduction. Research has shown that the probability of these behaviours varies with changing outdoor conditions (e.g. Nicol, 2001; Baker and Standeven 1997, de Carli et al. 2007; Haldi and Robinson 2009; Cândido et al. 2011; Schiavon and Lee 2013, Wang et al. 2018). Physiological adaptation (acclimatisation) serves to reduce thermal stress on the human body after repeated stimuli outside the comfort range on the cold or hot side. As a consequence, the response of the thermoregulation system is altered through adjustments in physiological parameters e.g. an enhanced metabolic expenditure (van Marken Lichtenbelt et al. 2014) or the onset temperature of sweating (Hori, 1995; Taylor, 2014). This shows that physiological adaptation requires exposures to non-neutral conditions, which in addition have been shown to have additional positive health effects (e.g. Hanssen et al., 2015; Pallubinsky et al., 2017). For example, Hanssen et al. (2015), and Schrauwen and van Marken Lichtenbelt (2016) have shown that excursions to the cold and warm side of neutral conditions improved the health status of patients with type 2 diabetes. Psychological

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holistic design: often also called whole building design, integrated design or collaborative design.

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adaptive mechanisms include for instance notions of perceived control, characterising the degree of control humans feel they have over their indoor environment facilitated e.g. by the availability of operable windows or the degree of privacy (e.g. Paciuk, 1990; Fountain et al., 1996; Hellwig, 2015, Boerstra, 2016); or changed expectations (Brager and de Dear, 2003; Strengers, 2008; Luo et al. 2016, Wang et al. 2017), e.g. due to pro-environmental attitudes (Leaman and Bordass, 2007). The range of acceptable indoor temperatures widens with a higher level of perceived control available to an individual. Schweiker and Wagner (2015) assign the largest effect to clothing level adjustments, i.e. a behavioural adaptation, followed by physiological adaptation especially on the warm side and psychological adaptation. This is supported by much earlier work of Cabanac, later also emphasised in the built environment context by Nicol and Humphreys (1973), which shows that behavioural adaptation is the one favoured by humans, hence the first to be applied. 3. Adaptive principles in current standards and guidelines In their early years of development, standards for the indoor environment mainly relied on the heat balance approach for providing thermal comfort criteria. Based on ASHRAE RP 884 worldwide database (de Dear et al. 1997), in 2004, ASHRAE was the first to include in its Standard 55 (ASHRAE, 2004) the adaptive approach as a method for naturally ventilated buildings. Based on the results of the European SCATs study (McCartney and Nicol, 2002), EN 15251:2007 (CEN, 2007), its imminent successor prEN 16798 (CEN, 2019) and ISO 177721 (ISO, 2017) provide a similar method for buildings not mechanically heated or cooled (free running). The second version of the Dutch ISSO 74 combines the heat balance model for heated spaces with an adaptive model based on the data from the SCATs database for the nonheating period (Boerstra et al., 2015). The use of the adaptive model depends on whether a space offers high degree of personal control. The Chinese Standard GB/T50785-2012 provides two methods for the evaluation of free-running buildings: 1) a method based on a similar formulation of the adaptive model as in ASHRAE Standard 55, and 2) a calculation method based on an adaptive predicted mean vote (aPMV) (Li et al., 2014). Both approaches offer different temperature ranges according to climate zones prevalent in China. India based its Model for Adaptive Comfort (IMAC) on field surveys in five Indian climate zones (Manu et al., 2016). The surveyed buildings comprise naturally ventilated, mixed-mode and air-conditioned office buildings. The IMAC approach considers explicitly mixed-mode buildings, which are becoming increasingly prevalent in India. Two adaptive models were developed, one for naturally ventilated and one for mixed-mode buildings. The equations have been included in the National Building Code 2017 (BIS 2017), the Energy Conservation Building Code 2017 and in building certification schemes. In the UK, the Chartered Institute of Building Services Engineers (CIBSE) have included the European adaptive model in three non-mandatory guides: “CIBSE Guide A: Environmental design” (CIBSE, 2015), TM52 on the assessment of overheating in non4

residential buildings (Nicol, 2013) and “TM59 Design methodology for the assessment of overheating risk in homes” (Bonfigli et al., 2017), all based on the European adaptive model of EN 15251 (CEN 2007), ISO 17772-1 (ISO 2017) and prEN 16798. Tables 1 and 2 summarise the standards and codes, which include the adaptive concept. As can be seen, the standards account for the applicability of adaptive models by categorising buildings or spaces. Unlike ASHRAE St 55 (ASHRAE 2017), EN 15251 (CEN 2007), ISO 17772-1 (ISO 2017) and prEN 16798 which use the classification of buildings into conditioned (centrally HVAC conditioned, heated or cooled), and occupant-controlled naturally ventilated or free running, ISSO 74 (Boerstra et al. 2015) has been using a classification according to the degree of personal control available in a space. The building types, alpha (high occupant control) and beta (low/no occupant control), are determined based on a flowchart of adaptive opportunities. As most of the buildings in the Netherlands (like in other European countries) do not only use one of the two main conditioning modes but a combination of them (van der Linden et al., 2006), this approach therefore evaluates combined options of occupant control. Using the criteria described in EN 15251 (CEN 2007), ISO 17772-1 (ISO 2017) and prEN 16798 (CEN 2019) to categorise the operation modes of buildings, it has become one planning option of consultancy companies e.g. in Germany to combine the heat balance model for the heating period and the adaptive model for the non-heating period (BNB 2015). This and other types of mixed-mode operation of buildings are common in many other countries. However, the various types of mixed-mode operation are not included in the standards and there is no consistency in the operation mode categories. The definitions used therefore have been criticised as ambiguous on the applicability of the adaptive model, especially for mixed-mode buildings (EBC 2018, Kazanci et al., 2019) which points to a need for clarifications in terminology. Tables 1 and 2 show that current classifications of buildings mainly consider the conditioning mode but no other building design characteristics, such as construction type (e.g. thermal mass, insulation), architectural features or spatial configurations (e.g. openings, layout, orientation, shading) or operation aspects, which also impact on a building’s ability to provide thermal comfort and affect the effectiveness of occupants’ adaptive responses (e.g. window design, orientation and internal openings affect the effectiveness of window opening for providing cooling). There is also a strong focus on behavioural adaptation and absence of the two other adaptive principles (physiological, psychological) discussed in section 2, and associated design and operational possibilities. The latest versions of ASHRAE St 55 (ASHRAE 2017) and ISO 17772-1 (ISO 2017) incorporate the effect of elevated air speed on comfort, which allows for wider acceptable ranges of operative temperature especially when occupants have control over the air speed. The inclusion of adaptive models in current standards and guidelines and the elevated air speed method are one step forward and help to avoid unnecessary use of active conditioning. However, the standards focus primarily on the allowable indoor temperatures

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without sufficient guidance for facilitating buildings and their operation designed to the adaptive comfort concept. Table 1. Terms, thermal comfort models and criteria used in current international standards for different building operation modes. Table 2. Terms, thermal comfort models and criteria used in current national standards for different building operation modes.

4. Making use of the adaptive principles In this chapter, we report on identified challenges and barriers and summarise exemplary information, which may contribute to a future guideline. We would like to point out that there is a strong interaction between the several factors mentioned, meaning that a change in one factor might require changes in another factor leading to different comfort or satisfaction perceptions (Humphreys and Nicol, 2018). 4.1. Contribution to lowering energy use in buildings Applying the adaptive principles in all kind of climates would most likely contribute to lowering the energy used in new and existing buildings (Yang et al., 2014; Barbadilla-Martín et al., 2018, Gokarakanda et al. 2019). But why can we expect this positive contribution? Humphreys and Nicol (2018) summarise that humans are found to live comfortable in diverse climates at temperatures between 15 and 35˚C. This means that the design temperature can be diverse and changes with the prevailing climate, facilitating a low as possible temperature difference between indoors and outdoors, resulting in a low demand for active conditioning. At the same time, there is more and more evidence, that thermal exposures slightly outside thermal neutrality lead to a wider range of accepted temperatures and can even have positive health aspects, as mentioned above e.g. an improved health status of patients with type 2 diabetes (Hanssen et al. 2015; Schrauwen and van Marken Lichtenbelt 2016). The wider range of temperatures can further lead to energy savings as they offer the potential to reduce the realised indoor-outdoor temperature difference and thereby the required actual cooling or heating capacity. Even in mechanically conditioned buildings there is potential to introduce a certain degree of thermal adaptation e.g. if the building is properly zoned. Henze et al. (2007) demonstrate that running a building following adaptive comfort criteria while optimising the control of thermal mass strongly reduces total cooling loads and associated building systems’ energy consumption. Using personalised comfort systems leads to an increased perception of personal control and allows the indoor temperature to be closer to the prevailing outdoor temperature, an effect called corrective power of personalised comfort systems (Zhang et al. 2015). Despite the clear energy saving potential outlined above, there are still challenges in achieving this desired outcome in practice. In permanently or seasonally conditioned spaces, rebound effects have been observed diminishing the effect of energy efficiency measures. For instance, rebound effects can occur due to i) a changed temperature regime (extent rebound), e.g. when occupants gradually decide for higher indoor temperatures during the heating period (e.g. Hansen et al. 2018), ii) a changed conditioning schedule (temporal rebound), e.g. intermittent, night set-back or shut-off vs permanent conditioning 6

(e.g. Gruber et al. 1989), iii) an extended availability of conditioning systems to more rooms (spatial rebound), e.g. entire apartment vs selected spaces of an apartment and iv) changed occupant behaviours (behavioural rebound), e.g. reducing the frequency or degree of changes in amount of clothing worn (e.g. Hansen et al. 2018, Karyono 2018). There are of course several sources of rebound effects. We mention here those related to thermal comfort and therefore relevant for building energy use. From a study in two mixed-mode office buildings in Jordan it can be seen that, although perceived control of the occupants and satisfaction was high, the occupant-driven room temperatures tended to be constant all year round. The occupants had access to decentralised air-conditioning units with adjustable thermostats (Al-Atrash 2018). Furthermore, it has been found that occupants, due to the adoption of western lifestyle, change e.g. their clothing behaviour towards more pieces of garments in warm and humid climates, requiring then lower temperatures to compensate for the warmer clothing (Karyono 2018). A study in University halls of residence in the UK found that students previously adapted to warm climates would create their preferred warm indoor environment in the new location given the choice and controls, leading to higher heating demand than designed (Amin et al., 2018). In a heating dominated region, it was found that occupants in energy-inefficient houses dressed warmer than occupants in energy-efficient houses (Hansen et al. 2018). Certain behaviours and controls’ use can therefore reverse the energy conservation potential of adaptation, unless appropriate measures are in place. 4.2. Challenges in understanding the adaptive principles The conceptual model behind the bivariate relation of indoor operative temperature to outdoor temperature is far more sophisticated. It qualitatively describes the impact of influencing factors, which are not part of calculation models of adaptive thermal comfort. It is often described as a black box model. Furthermore, some qualitative factors of the conceptual model are outside the classic educational training of building designers (behavioural adaptation, psychological adaptation). Acclimatisation, as one contributor to physiological adaptation, might be necessary to be communicated again, as it has not been part of the common understanding of thermal comfort anymore since the 70ies. Some missing links towards a full understanding of acclimatisation processes within humans remain for future research. In the context of overheating, Hellwig (2018) discusses whether using the term adaptation might be the source of reservations among stakeholders towards the adaptive model, as they would expect adaptation being related to a stressful situation. On one hand, the bivariate representation of the adaptive approach makes it attractive for dynamic thermal building simulation. On the other hand, for building designers in the planning process, who have been trained according to the previous common understanding of steady state, a black box model incorporating non-quantifiable factors appears to be a source of difficulty and uncertainty when deciding for a building’s design. As thermal comfort has often been explained using the term “satisfaction” (ASHRAE 2017), there is a need to explain under which circumstances occupants tend to be satisfied. 7

As numerous studies have shown, there is a range of variables which can neither be measured nor simulated, as mentioned earlier, personal control, expectations or level of acclimatisation etc. Excellent summaries on these factors are available e.g. by the Usable Buildings Trust2, or e.g. Humphreys and Nicol (1998). Definitions for conditioning modes depend on how the conditioning practice in a certain country uses the term. Whereas natural ventilation for instance has often been used as a synonym for free-running buildings, in some countries, natural ventilation refers exclusively to the way indoor air is exchanged with outdoor air. Meanwhile, ASHRAE (2017) uses the term occupant-controlled naturally conditioned space. The term mixed-mode building is often used for buildings with a combination of natural ventilation and mechanical conditioning, mainly using air in alternating operation or seasonally (Kalz and Pfafferott 2010, Brager and Baker, 2008; Manu et al. 2016). EN 15251 (CEN 2007) uses the term building without mechanical cooling and defines at the same time that the heating system should not be in operation. Active cooling is used as synonym for mechanical cooling, covering both cooling of air and thermally activated systems (building elements or chilled panels). Regionally common definitions may vary, and therefore, the guideline currently under development can provide an overview over the terms often used and their meaning. 4.3. Local climate, season and acclimatisation The main driver of human adaptation in buildings with a certain connection to outdoor climate (i.e. free-running buildings) is the local climate and its seasonal course. If exposed, humans adapt to the prevailing outdoor climate, and their indoor comfort temperature is strongly related to the outdoor temperature they experience (Humphreys, 1978). It has been frequently reported that people in hot climates are able to feel comfortable at temperatures much higher than those from cold climates (Humphreys & Nicol 1998; van van Hoof 2008; Brager & de Dear 1998) and people from different climate zones have different tolerance to cold and warm indoor environments, which is attributed to an extent to physiological adaptation due to exposure to non-neutral thermal conditions. Seasons also contribute to the formation of thermal experience. Seasonal changes provide people with enough time to adapt to their different thermal environments. Wang et al. (2010, 2014) showed that human neutral temperature varied in different seasons and it was higher in summer and spring than in winter. Cao et al. (2011) found that low outdoor temperature during winter made people adapt to the cold environment while in the summer people had a higher tolerance to the hot environment. Humphreys’ meta-analysis of thermal comfort studies concluded that people within a population can tolerate seasonal drifts in the indoor temperature of up to 7 to 8 Kelvin (Humphreys et al., 2016). Indoor and outdoor climates have a mutual influence on occupants’ adaptability. The relationship between the mean indoor temperature and people’s comfort temperature has been found to be strong (Humphreys, 1976; Auliciems 1981, Ning et al. 2016) which means that people are able to match their comfort temperature to their typically experienced

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http://www.usablebuildings.co.uk/ last accessed: 3 Sept 2019

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environment. Li et al. (2018) found that occupants living in the unheated thermal environments in the South-east China zones are more adaptive and tolerant to cooler winter indoor conditions than those living in the North part of China where central heating systems are in use. Similarly, occupants in social housing apartments in the UK were found to have adapted to the high and stable indoor temperatures they were exposed to (Teli et al., 2016). Wang et al. (2018) found that the participants were more sensitive to temperature variations at the early heating phase. They adapted to a warm heated environment gradually during the whole winter. The above research shows that thermal experience in different climates and indoor thermal environments affects people's physiological adaptation and expectations, forming different subjective thermal responses and neutral temperatures. Such effects of climate and seasons need to be considered in the development of the planned guideline to avoid the adoption of a universal design approach that would disregard climate and human adaptability, leading to a higher energy use than necessary. Furthermore, a number of adaptive comfort models have been developed for different climate zones (e.g. Manu et al. 2016, Toe 2018). The planned guideline cannot introduce all of them. However, a collection of models could be included in a repository and described in a more general way. 4.4. Local constraints and further contextual factors Certain building usages require more or less constant thermal conditions all-year-round, such as museums. Also, public indoor spaces are certainly to be looked at in a different way than e.g. offices or homes. The latter spaces offering a higher degree of privacy are predestined for the application of the adaptive approach, which considers adaptive actions of occupants as an essential basic part of comfort creation and perception. There are individual differences in attitudes: For example, Leaman and Bordass (2007) or Deuble and de Dear (2012b) found that occupants with a higher level of environmental concern are more likely to tolerate conditions beyond the “ideal” in green buildings compared to occupants with a lower level of environmental concern. Personality and openness to receive information on the building differ between persons. Occupants can have increased expectations due to culture, modernity, lack of adaptation to outdoors, or a learned attitude. An extensive review of the various factors affecting people’s adaptive behaviours in different building types can be found in Korsavi et. al (2018). There are further contextual factors, often local constraints or social norms, which should be taken into account when designing buildings or considering bioclimatic/ passive design strategies. Such factors can limit the opportunities for a functioning adaptive design: - Outdoor air pollution and noise - Urban heat island effect, limiting the effectiveness of natural ventilation in non-airconditioned spaces - Disease transmitting insects - Security issues - Requirements regarding other building planning aspects e.g. fire safety - Cultural custom (e.g. dress code) 9

- Space scarcity in highly populated areas limiting opportunities to design for natural

ventilation - Real Estate Company planning – difficulties in involving occupants in the planning phase - Technological challenges, e.g. typical air-conditioning set-point control is based on airtemperature These challenges can probably not be addressed by an improvement of a standard alone. For several cases, a guideline may be supportive in developing design solutions for some items as addressing these issues may lead to more awareness about the missing design solution. It can also be seen that many of these constraints are related to highly urbanised areas in the more extreme climates. 4.5. Adaptive responses, personal control and user behaviour Fundamental to the adaptive approach is the role of the user: “If a change occurs that produces discomfort, people tend to act to restore their comfort.” (Humphreys and Nicol 2018). In frequent discussions amongst professionals at energy efficiency symposia where user behaviour is addressed, we have experienced many building professionals’ subjective perception that occupants’ behaviour would be random or not logical, and in many cases contradictory to a low energy use of a building, e.g. window opening at “wrong” conditions or using thermostats in a “wrong” way (see further examples Usable Building Trust2). They define the user’s role according to their self-image as professionals, marketing strategies for new building technologies or design solutions promising increased comfort through comfort provision, which literally assigns a passive role to users (Hellwig 2018). The degree of control was identified in many studies as a main driver for thermal comfort or satisfaction (e.g. Leaman and Bordass 2006, Hellwig, 2005, Schweiker et al. 2018). Regarding the impact of control on comfort perception or satisfaction, a conceptual model was presented in Hellwig (2015), showing that social norms, expectation (e.g. Fountain et al., 1996; Brager and de Dear, 2003) and psychological factors can support or limit adaptive opportunities. When expectations are not met this may result in complaints during building operation (Bischof et al. 2002). It is important that a user has realistic expectations which are consistent with the performance of the building after the building is commissioned, otherwise this can lead to disappointment (Usable Building Trust2). Research has shown that occupants’ satisfaction decreases with a higher number of persons in the same room, which can be attributed to a lower degree of perceived control and higher social interactions necessary (Hedge et al., 1989; Duval, Charles and Veitch, 2002; Marquardt, Veitch and Charles, 2002; Wagner and Schakib-Ekbatan, 2011; Al-Atrash 2018). As an example, Schweiker and Wagner (2016) showed that the number of occupants in a room with elevated temperature alters the adaptive opportunities used by occupants: less ceiling fans and blinds were used in four person offices compared to single person offices, but more clothing level adjustments occurred in larger offices. In addition, perceived control and neutral temperature decreased with a higher number of persons. Hence, designing for high personal control in open-plan offices is challenging due to a generally 10

diminished perception of privacy. However, Leaman and Bordass (2006) argue that individual control in an open office can be perceived as high as long as there is a means of changing the environment, e.g. by calling facilities’ management and having the request resolved quickly. A layout of work spaces which provides individuals with sufficient space and means for adjustments and privacy can increase perceived control and satisfaction levels. There are several recent activities (e.g. IEA EBC Annex 66, 2019, IEA EBC Annex 79, 2019) and review papers regarding the state of the art on behaviour and control (Schweiker et al. 2018, Hellwig, 2015). With regard to the energy use of buildings, behaviour has been identified to be as important as the energy efficiency quality of the building design (GramHanssen, 2013). A huge variety of different adaptive behaviours exists, which people can choose to make themselves more comfortable. Table 3 shows conceivable adaptive actions or responses to warmer or cooler than previously experienced environments, sorted according to their effect principles. Schweiker et al (2018) categorised adaptive actions into physiological, individual, environmental and spatial adjustments. The building usage/type (e.g. residential, office, classroom etc.) may reduce the number and type of conceivable adaptive actions as it e.g. may not be appropriate to use a blanket when sitting in a classroom or taking off more clothes in an office environment. Conceivable adaptive actions may also differ according to the local climate. For instance, measures such as wetting of walls or floors can be ineffective in warm and humid regions compared to hot and arid climates. However, although an adaptive action may be more suited to a certain season, climate or building type, it may also be applicable in a different context depending on time of the day or occupancy. In sight of climate change, adaptive actions previously not used in a certain region may become desirable and appropriate in the future. In the planned guideline, some basic principles for designing for occupant control should be implemented. There are still common misunderstandings in the interpretation of personal control among building planners and operators regarding the amount of control, the seriousness of this topic and the level of information needed by occupants (Hellwig and Boerstra 2017, 2018). It might be supportive to include an exemplary list of design decisions or operational practices not conducive to high perceived control, as they impose restrictions to occupants. Hellwig (2018) points out that behavioural actions might not only help to adapt to a stimulus but also to remove this stimulus, e.g. by using technological means; hence if the technology used has enough capacity to fully remove or avoid the stimulus physiological adaptation (acclimatisation) to the deviating conditions will not take place. In order to avoid this, energy efficient solutions can be chosen. Provided the users are conscious about the “green” performance of their building and understand its importance, the controls are usable and they received factual information on how to make use of certain technological means to adapt, they will be able to use their building in the intended way (Leaman and Bordass 2007; Deuble and de Dear 2012b, Usable Building Trust2).

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For building operation, it is important not to discourage the user from taking control actions. For overall satisfaction, it is supportive if an occupant – to a certain degree - feels responsible for the indoor climate at their workplace. Otherwise, the occupant has to rely too much on a building’s autonomic behaviour or changes to be implemented by the facility manager which can be stressful as it is indirect control (Johnson, 1974). To facilitate satisfaction of the users an appropriate complaint strategy system of the facility management of the building is desirable. This includes that complaints of users are taken seriously and comprises an appropriate feedback loop. In this paper we have not included personalised comfort systems as this will be the outcome of another activity of Annex 69. Table 3. Conceivable adaptive actions or responses to warmer or cooler than previously experienced environments; adopted from Humphreys and Nicol, 1998; Nicol and Humphreys, 2018, Schweiker et al. 2016; Taylor 2014, van Marken Lichtenbelt et al. 2014, further inspiration from R.F. Rupp and N. Brito see acknowledgement, and adjusted, re-arranged and amended by the authors. Adaptive actions are seen as predominantly conscious behaviour; adaptive responses (in italic letters) are seen as predominantly autonomous unconscious physiological reactions of the body.

4.6. Building design and operation The standards describe under which operation mode(s) the adaptive model can be applied. The underlying assumption is that the building’s design is capable for this operation mode, namely is designed according to bioclimatic/passive design principles. However, the standards do not explicitly state this nor potential issues in applying them in practice. On the one hand, modern construction, conditioning technologies and lack of suitable bioclimatic/ passive building design for multi-storey buildings have led to construction and conditioning practices in many regions of the world, which are different to their traditional, vernacular approach. Looking at prevalent building designs all over the world it appears to be necessary to include this kind of advice into the standards. On the other hand, there are limitations in the application of bioclimatic design, e.g. local constraints (see also section 4.4.). For example, in dense urban areas, high-rise buildings tend to overshadow each other so that opportunities for passive solar heating and daylighting are limited. At the same time, overshadowing in warm climates can also lower the cooling needs, which demonstrates the interrelation of design approaches with the prevailing climatic and urban context regarding their energy impact. So far, there is few examples of passive design features included in the standards as e.g. shutters. At the same time, passive design is more: it is about thermal mass, night ventilation, solar protection or shading, use of passive or active solar technologies etc. in a balanced way and where relevant. It is outside the scope of the planned guideline to repeat passive/bioclimatic design principles for different climatic zones which have been published elsewhere (e.g. Kubato et al. 2018, Manzano-Agugliaro et al. 2015; Zhai and Previtali 2010; Manu et al. 2019, Kwok 2018). Nevertheless, basic principles need to be introduced in order to show their relationship to the adaptive principles as well as potential constraints in their application and possible ways to address them.

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The layout of a floor plan, fenestration and positioning of openings, thermal properties of materials used in the envelope or in internal building elements, room height and depth do not only affect the readiness of a building for the free-running mode. These parameters also affect the choice of the conditioning systems affecting energy efficiency and the level of personal control of the occupants. In an open plan office, it might be difficult to provide individual access to windows although it might be still possible to implement natural ventilation. There is a time lag of about one week in clothing adaptation for short-term changes in the weather (Humphreys and Nicol, 1998) and of up to two weeks for physiological acclimatisation to heat for sudden changes (Taylor 2014), e.g. in a heat wave. The time lag in human adaptation to changing outdoor conditions is represented in the calculation of the outdoor running mean temperature (McCartney and Nicol 2002, EN 15251 2007 and successors, ASHRAE 2017). Buildings designed according to the adaptive principles should therefore provide sufficient buffer to allow occupants to adapt (Hellwig 2018). The ability of a building to buffer is highly linked to the predictability and reliability of a building’s thermal behaviour, which is an important building property for occupants (Bordass and Leaman 1997). Therefore, a successful building design implementing the adaptive comfort principles is one that aims to maximize use of passive potential, regardless of the type of usage or the operation mode. In order to facilitate human thermal adaptation to changes in the prevailing outdoor weather the building has to be designed so that: a) it provides a sufficient environment-regulating capacity within the building construction and enclosure, and b) it makes use of adequate technological opportunities enhancing the thermal environment if what is mentioned under a) is not sufficient. Therefore, it can be stated that a successful adaptive thermal comfort design is one in which design for human thermal adaptation is foreseen, planned, and carefully embedded in the design and operation intent. Three general types of buildings are considered in their different relation to design for adaptive thermal comfort: 1) Naturally ventilated, free-running, passive buildings, 2) Mixedmode buildings, and 3) mechanically conditioned, actively conditioned, air-conditioned buildings. These types of buildings offer occupants different degrees of thermal adaptation and thermal environmental control. 1) Naturally ventilated, free-running, passive buildings: The performance of freerunning buildings depends solely on their passive design and the external weather conditions. Therefore, the adaptive concept to thermal comfort is appropriate for evaluating the effectiveness of passive systems (Chiesa et al. 2017). All definitions known to the authors define the availability of operable windows as necessity. Some standards state that conditioning systems should not be in operation (ISO 17772-1 (2017)/ prEN 16798) others state that conditioning systems should not be installed (Construction and Planning Agency Taiwan, (2018)). Flexible clothing policies as an organisational factor is required (ASHRAE 2017, ISO 17772-1 (2017)/ prEN 16798). Ceiling fans are seen as mandatory in

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climates where air-movement is a desirable strategy to increase heat loss of the body (Construction and Planning Agency Taiwan, 2018, National Building Code India, BIS 2017). 2) Mixed-mode buildings: Several definitions of the term “mixed-mode” exist. Brager (2006) defines a mixed-mode building as a hybrid combination of natural ventilation (operable windows: manually or automatically controlled), and mechanical systems (including air distribution equipment and refrigeration equipment for cooling). This definition describes the situation of mixed-mode in climates where cooling using air is prevalent. It does not provide information whether heating in general or predominantly radiative systems for both cooling and heating is covered by this definition. EN 15251 (CEN 2007) and its successors exclude the heating case from the scope of application of the adaptive model. The operation of mixed-mode buildings can be in concurrent (same space, same time), change-over (same space, different times) in either permanently alternating mixed-mode or in seasonal mixed-mode, or zoned-mode (differed spaces, same time) (Brager 2006). In some national codes mixed-mode is defined by the operation of AC only during extreme outdoor conditions (National Building Code India, BIS 2017) and with extreme orientations (Construction and Planning Agency Taiwan, 2018). For these types of buildings, a façade design is required which is suitable to the building context (local climate, building type/usage, local constraints). There has been a discussion on whether mixed-mode buildings can be planned or assessed using adaptive comfort models. There is evidence (Brager and Baker, 2008) that in mixed-mode buildings, indoor temperatures “can be allowed to float within the more energy-efficient acceptability limits of the adaptive comfort standard and still ensure comfortable conditions for the occupants. When temperatures reach the maximum limits then HVAC systems can be turned on in a limited way to ensure temperatures stay within the adaptive comfort standard limits (rather than switching to the narrow set points of a centrally-controlled AC building)” (Deuble and de Dear 2012a, p.59). Research by Luo et al. (2015) brought evidence that the adaptive model is applicable to mixed-mode buildings especially when natural ventilation is utilised. The CIBSE AM13 (2000) explains in detail the principles and best practices in the design of buildings for mixed-mode ventilation. Deuble and de Dear (2012a) indicate that mixed-mode ventilation requires intelligent control systems that switch automatically between natural and mechanical modes to minimize energy use without compromising air quality and thermal comfort. Mixed-mode ventilation has – in a European context – also been called hybrid ventilation (Heiselberg, 2002). Further discussion about a more general definition of mixed-mode buildings with examples for typical applications in exemplary climates seems to be necessary. 3) Mechanically conditioned, air-conditioned, actively conditioned buildings: These buildings can be heated or cooled, either with water-based systems (predominantly radiative systems) or based on air (air-conditioning). The operation of these systems can be either centralised or decentralised, whereby centralised operation tends to offer the lowest degree of personal control. Decentralised systems offer more control. If combined with 14

operable windows the question could be raised whether they fall under the “concurrent” category of mixed mode buildings. A source of misunderstanding has been the comfort classes/categories introduced in some standards (A, B, C or I, II, III) for design and operation of buildings. Although explained e.g. in EN 15251 (CEN 2007), ISO 17772-1 (ISO 2017) and prEN 16798 as the level of expectation they are often interpreted as level of quality, with tight indoor climate control seen as superior (Nicol and Wilson, 2011). For example, sustainability rating systems, such as the German BNB (2015), award more credits for class A/category I buildings. Class A/ category 1 stands for high expectation and is meant to be applied for very sensitive people, vulnerable groups who might be sick or restricted in their possibilities to adapt, either because of missing ability to sense temperature (as e.g. for dementia) or because of disability in changing clothing without the help of others. As could be shown by Arens et al. (2010), no relative satisfaction benefit could be found for class A/category 1 buildings. Conditioning practices have been changing since the invention and broader implementation of central conditioning systems and there is a clear tendency to condition entire spaces as well as conditioning over long periods. We should therefore consider that people have likely adapted to their often experienced indoor environments. The temperature experienced in these spaces is likely the typical set-point (design) temperature according to a country’s standards or regulations. They experience a “normal” environment (Humphreys and Nicol 1998). This does not necessarily mean that they cannot be comfortable at changed temperatures but if changes in the building’s temperature operation are intended (in order to improve energy-efficient building operation) this would require an appropriate communication of the topic. From the start of planning to beyond the commissioning, users should be involved in the decision-making processes as part of an intensive communication strategy, whenever possible. This avoids misunderstandings, minimises misconceptions and enables participation. Involving occupants from the beginning is of course more difficult in cases of buildings built on the real estate market for unknown tenants. In such cases ‘sample occupants’ or pre-defined sets of ‘sample occupants’ could be used during the design phase to cover the variety of users expected for the building in question. An additional consideration is the transfer of design intentions into the building usage and operation phase by means of information processes, e.g. digital “manuals” of the building tailored to future occupants and available to them, even without the involvement of the real estate owner. Overall, stronger effort for user information and involvement as well as fine-tuning of the building systems would need to be placed in the operational phase of the building in order to compensate for their absence in the design phase. The advantages of involving occupants are two-fold: 1) learning their thermal needs and experiences, motivating them and managing their expectations, and 2) informing them about the building, its environmental systems, the expected environmental variability and effects on performance, and most importantly about their role in controlling their own thermal environment and its impacts on building performance. As explained by Leaman and 15

Bordass (2007) “…if people understand how things are supposed to work and what they are for – window controls, perhaps, or thermostats – they tend to be more tolerant if things do not turn out quite as well as they should”. Thus, a greater knowledge and understanding of building environmental features and controls can lead to a relaxation of comfort expectations, with significant implications for energy use (Brown and Cole 2008). In the UK, a process has been developed called "Soft Landings" to help implement structural and technical measures for sustainable buildings ("The Soft Landings Framework" 3). Similar approaches exist in other countries. Furthermore, research is focussing on how to involve users in the design and operation process of buildings (e.g. Martek et al. 2019, Bull and Janda 2018). 5. Framework for adopting the adaptive principles Based on the considerations in the previous sections we developed a framework to support the adoption of adaptive principles in building design and operation. Hereby we focus on those elements of a holistic design process which we identified being primarily relevant to the adoption of adaptive principles (Figure 1). The primary elements of the framework are: the building context, adaptive principles, planning/design, adaptive responses/actions and the operational planning/operation of the building, which are described below with links to the corresponding sections. Building context: As derived from the discussion, the local climate (section 4.3), local constraints (section 4.4), building type and its use (section 4.4, 4.6) and the local social norms (section 4.5) determine the way adaptive principles (section 2) apply to a specific building context. It should be highlighted that the adaptive principles are not influenced by the building context, since they are based on fundamental physical, physiological and psychological concepts. However, their potential is moderated by the building context. For instance, in a warm climate, occupants are expected to accept warm indoor conditions (psychological and physiological adaptation to a warm climatic context) rather than in a cold climate. The moderated adaptive principles then feed into the design, operational planning and operation of the building. Planning/design (section 4.6): Priority is given to passive design, envelope and construction methods to filter and moderate the weather variability. These are then supplemented or enhanced if needed by use of active systems and technologies (building services design), ranging from fans to simpler mechanical systems. In parallel, appropriate adaptive opportunities are designed to ensure the occupants’ ability to adjust their indoor environment. They depend on the building’s passive and active design and vice versa, if a certain adaptive opportunity should be available to the users, then passive and active design are to be designed in such a way that this opportunity can later on perceived as an opportunity. This design process is iterative, as every design decision affects the others. Adaptive responses/actions: Based on the three adaptive principles: behavioural, physiological and psychological adaptation and through the building’s context and design,

3

www.softlandings.org.uk last accessed 3 Sept 2019

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possible adaptive actions are defined (4.5). Although not comprehensive, Table 3 presents an extended collection of adaptive actions, which serve also as a basis to determine operational strategies and approaches. Operational planning/operation: In this phase, actors play the most significant role for the effective implementation of adaptive actions. Occupants’ participation is encouraged not only when the operational phase starts but already in an early design and operational planning stage to learn their needs and later inform them on how to use the building in the intended way (section 4.6). The organisational management and operator (facility manager FM) need to develop an operational strategy that involves and facilitates adaptive actions. This process may then feed information back to the design brief for the building’s service systems and adaptive opportunities design. During operation, an efficient feedback loop between the actors can ensure that issues are identified and addressed promptly. The framework aims to support and complement a holistic building design1 approach and not to replace it, as it does not include all possible design criteria but focuses on the inclusion of adaptive principles in the process.

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Figure 1: Proposed framework for adopting the adaptive principles in planning and operation of buildings. For the “Adaptive responses/actions” refer to Table 3. 6. Outlook In this paper, we reported on the challenges and gaps in using the adaptive thermal comfort approach to lower the energy use in buildings. We identified those areas, which need to be addressed in the planned design guideline on adaptive thermal comfort. We have done so based on our understanding that human thermoregulation and the physical principles of heat exchange between humans and their environment form one basis of adaptive thermal comfort, yet do not represent the complete set of variables of this comprehensive approach towards thermal comfort. Although not quantifiable or sometimes not solely in control of building planners, and therefore identified being a source of uncertainty for them, building contextual factors play a major role. Therefore, as expressed earlier by Humphreys and Nicol (2018): “The adaptive model does not fit easily into the current way of expressing standards for thermal comfort”. 18

Designing buildings according to the adaptive principles requires an occupant-centred and climate-centred approach that realises synergistic building-occupant controlled indoor environments in response to the prevailing outdoor weather. Implementing this approach involves many challenges and complexities that demand a collaborative effort1 between the several building disciplines towards a common goal: achieving comfortable, satisfying indoor environments sustainably. The developed framework forms now our basis to develop the guideline. We are seeking to find a balance between providing concrete guidance on one hand and on the other hand enhancing creative thinking to be open for new low energy facilitating solutions, not limiting solution to what we know currently or are used to. Another challenge lies in adequately considering the requirements resulting from our diverse climates, acknowledging both today’s and future climates or seasons, which may not allow for a freerunning mode at all times, but facilitating free-running modes in building operation as often as possible. We have not discussed personalised comfort systems (PCS) in this paper as they will be an outcome of another Subtask activity of Annex 69 but will be included in the final guideline. Through the discussion in this paper, the following specific objectives for the guideline have been identified: 1) To improve the overall understanding of the adaptive principles; 2) To explain the adaptive principles’ relation to building energy use; 3) To help interpreting the adaptive model in building practice; 4) To include advice for heated or cooled buildings into the guideline, not limiting the application of the adaptive thermal comfort concept to free running buildings, especially, how to use the adaptive principles in permanently or long-season conditioned spaces. The guideline will address multiple stakeholders, i.e. building practitioners, including building planners (architects, engineers, sustainability certification consultants/councils) and building operators (facility managers, owners, tenants). It will also be a useful source of knowledge and guidance for educating future building professionals. As the guideline is meant to enhance the knowledge about the application of the adaptive principles, it should provide supportive exemplary solutions from practice and different climates. Case study buildings of Annex’ 69 (EBC 2018) Subtask C form one source for these examples. It will form the basis for an improved description of criteria for the application of the adaptive approach in standards. Insofar, the guideline we can now develop based on the framework presented here, aims to support a successful adaptive thermal comfort design in which design for human thermal adaptation is foreseen, planned, and carefully embedded in the design and operation intent. 7. Acknowledgement This work has been performed within the framework of the International Energy Agency - Energy in Buildings and Communities Program (IEA-EBC) Annex69 “Strategy and Practice of Adaptive Thermal Comfort in Low Energy Buildings”. www.iea-ebc.org, www.annex69.org The authors would like to thanks Fergus Nicol from the Network of Comfort and Energy Use 19

(NCEUB) for his support in our inquiry to NCEUB on table 3, Dr Ricardo Forgiarini Rupp from Federal University of Santa Catarina, Florianópolis, Brazil and Nelson Brito from University of Coimbra for their amendments to table 3, the reviewers for their valuable and constructive comments. Runa T. Hellwig would like to thank the Obelske Familiefond, Denmark for supporting this work. Marcel Schweiker’s participation was supported by the project "Thermal comfort and pain" funded by the Heidelberg Academy of Sciences and Humanities. Joon-Ho Choi appreciates technical assistance from Ms. Zhihe Wang, a student of the School of Architecture at the University of Southern California in the U.S. Rodrigo Mora was supported by the Green Value Strategies Fund, BCIT. Zhaojun Wang was supported by the National Natural Science Foundation of China (No. 51278142).

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Declaration of interest

We wish to confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome. We confirm that the manuscript has been read and approved by all named authors and that there are no other persons who satisfied the criteria for authorship but are not listed. We further confirm that the order of authors listed in the manuscript has been approved by all of us. We confirm that we have given due consideration to the protection of intellectual property associated with this work and that there are no impediments to publication, including the timing of publication, with respect to intellectual property. In so doing we confirm that we have followed the regulations of our institutions concerning intellectual property. We further confirm that any aspect of the work covered in this manuscript that has involved either experimental animals or human patients has been conducted with the ethical approval of all relevant bodies and that such approvals are acknowledged within the manuscript. We understand that the Corresponding Author, Runa T. Hellwig, is the sole contact for the Editorial process (including Editorial Manager and direct communications with the office). She is responsible for communicating with the other authors about progress, submissions of revisions and final approval of proofs. We confirm that we have provided a current, correct email address which is accessible by the Corresponding Author and which has been configured to accept email from

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Tables and Figures Captions Table 1. Terms, thermal comfort models and criteria used in current international standards for different building operation modes. Table 2. Terms, thermal comfort models and criteria used in current national standards for different building operation modes. Table 3. Conceivable adaptive actions or responses to warmer or cooler than previously experienced environments; adopted from Humphreys and Nicol, 1998; Nicol and Humphreys, 2018, Schweiker et al. 2016; Taylor 2014, van Marken Lichtenbelt et al. 2014, further inspiration from R.F. Rupp and N. Brito see acknowledgement, and adjusted, re-arranged and amended by the authors. Adaptive actions are seen as predominantly conscious behaviour; adaptive responses (in italic letters) are seen as predominantly autonomous unconscious physiological reactions of the body. Figure 1: Proposed framework for adopting the adaptive principles in planning and operation of buildings. For the “Adaptive responses/actions” refer to Table 3.

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Table 1. Terms, thermal comfort models and criteria used in current international standards for different building operation modes Standard

Building operation mode Free-running

Mixed-mode

Conditioned

ASHRAE Standard 55 (2017) Term - Occupant-controlled naturally - Not defined conditioned spaces Model - Adaptive model

- Any space - Heat balance model

Criteria - No mechanical cooling system installed

- Applicable for all buildings - No specific criteria defined

- No heating system in operation

- Near sedentary physical activities with metabolic rates ranging from 1.0 – 1.3 met

- Avoid strict clothing policies inside the building

- Prevailing mean outdoor temperature is: 10°C
- Operable windows to the outdoors operated by the occupants

- Mechanical ventilation with unconditioned air may be utilized in addition to operating windows ISO 17772-1 (2017)/ prEN 16798 [superseding EN 15251 (2007)] Term - Buildings without mechanical cooling Model - Adaptive model

- Not defined

- Heated and/or mechanically cooled buildings

- Heat balance model and

- Heat balance model

adaptive model seasonally alternating Criteria - No mechanical cooling or heating in operation

- Operable windows or comparable facade components operated by the occupants

- Mechanical ventilation with

- Applicable for all buildings combining the heat balance - No specific criteria defined model for the heating period and the adaptive approach for the non-heating period, e.g. in German sustainability certification systems

- Common planning practice:

unconditioned air may be utilized in addition to operating windows

- Other low-energy methods of personal control such as fans, shutters, night ventilation etc.

- Near sedentary physical

29

activities with metabolic rates ranging from 1.0 – 1.3 met

- Avoid strict clothing policies inside the building

- Running mean outdoor temperature is: 10°C
30

Table 2. Terms, thermal comfort models and criteria used in current national standards for different building operation modes Standard

Building operation mode Free-running

Mixed-mode

Conditioned

Dutch ISSO 74 Term - Not defined Model

- Alpha

- Beta

- Heat balance model (heating) - Heat balance model (heating), and adaptive model (nonheating) seasonally alternating

Criteria

adaptive model (transition), heat balance model (cooling)

- Criteria set through the use of - Criteria: set through the use a flowchart

- With occupant control - Free-running conditions in non-heating period with operable windows and other adaptive opportunities

- Non-strict clothing policy

of a flowchart

- Without or low occupant control

- Spaces/zones heated in winter or actively cooled spaces, cooling clearly perceivable by occupants

- Actively cooled spaces, cooling not clearly perceivable by occupants Chinese GB/T50785-2012 Term - Free-running buildings Model - Two options: a) adaptive models for different climate zones or

- Not defined

- Heated or cooled spaces - Heat balance model

- b) adaptive predicted mean vote (aPMV) Criteria - The adaptive model can be used for two groups of climate zones:1) severe cold area and cold area, 2) hot summer - cold winter, hot summer - warm winter, and temperate area

- When using centralised air conditioning, the outdoor air volume should comply with the relevant national standards

- Adaptive predicted mean vote (aPMV) conditions are available for climate zones according to 1) and 2) as well

- Proper natural ventilation measures should be used

- Mechanical ventilation/fans can be used but no heating or cooling devices (National Code) National Building Code 2017 India, Energy Conservation Building Code 2017 India based on Indian IMAC (Voluntary Program) GRIHA – Green Building Rating System based on Indian IMAC

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Term - Naturally ventilated (NV)

- Mixed mode

Model - Adaptive model for NV - Adaptive model for mixed buildings based on Indian data mode buildings based on Indian data Criteria - No mechanical cooling or air- - AC is operated only during conditioning systems installed extreme outdoor conditions

- Air-conditioned (AC) - Heat balance model based on ASHRAE St. 55

- AC always in operation

- Ceiling fans and operable windows available

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Table 3. Conceivable adaptive actions or responses to warmer or cooler than previously experienced environments; adopted from Humphreys and Nicol, 1998; Nicol and Humphreys, 2018, Schweiker et al. 2016; Taylor 2014, van Marken Lichtenbelt et al. 2014, further inspiration from R.F. Rupp and N. Brito (see acknowledgement) and adjusted, re-arranged and amended by the authors. Adaptive actions are seen as predominantly conscious behaviour; adaptive responses (in italic letters) are seen as predominantly autonomous, unconscious physiological reactions of the body categories of adaptive actions or responses

adaptive actions/ responses to adaptive actions/ responses to warmer than cooler than previously previously experienced environment experienced environment

regulating the rate of internal heat generation

- increasing the level of activity - relaxing, exposing oneself to

-

regulating the rate of body heat loss

-

-

become acclimatised (nonshivering thermogenesis) eating a high-caloric or hot meal increasing muscle tension drinking a warm beverage rubbing hands shivering thermogenesis (quite extreme and not conceivable) vasoconstriction adding clothing or blankets curling up or cuddling up selecting different clothing material closing doors and windows (reducing air movement) exposing oneself to the sun sitting close to a heat source (masonry heater, fire, radiator) relaxing, exposing oneself to become acclimatised having a warm bath or shower sleeping in family group with the bodies pushed up against each other

- reducing the level of activity - relaxing, slowing down one’s life - relaxing, exposing oneself to become

acclimatised (reduced internal heat production, earlier on-set of vasodilation) - adopting siesta-routine (matching level of activity to diurnal temperature course) - eating less or low caloric food - having cold food

-

-

regulating the thermal environment

- insulating the loft or wall -

-

selecting a

cavities (long-term effect) improving the windows and doors (long-term effect) closing windows or doors letting the sun enter indoors adjusting or turning the thermostat on or lighting a fire notifying the facility management

- finding a warmer spot in the

vasodilation taking off some clothing adopting an open posture opening a window for getting a breeze leaning against a cool wall (high thermal inertia) sitting on a stone bench in the shadow sweating relaxing, exposing oneself to become acclimatised (increased sweat rate, redistribution of sweat, lowered sweat on-set temperature) drinking more (stay hydrated) drinking a cup of tea (induces sweating more than compensating for its heat) drinking cold beverages using a hand fan having a cool shower (water at room temperature) having a bath in the sea or a lake

- opening a window - switching off heat emitting equipment not

needed activating shading in front of a window using night time ventilation adding shading for walls wetting the floor ventilating the attic space switching on a fan adjusting thermostat or turning on the airconditioner - notifying the facility management - finding a cool spot in the house -

33

different thermal environment

house or going to bed - visiting a friend or going to

the library

- sitting under a tree - going for a swim - sleeping outdoors under clear sky e.g. on the

- building a better house (long-

term way of finding a warmer spot) - emigrating

-

-

modifying one’s psychological perception

- letting the mind adjust so that it becomes used to cooler environments - holding a warm cup of tea (alliesthesia)

roof top sleeping in the basement visiting a friend or a shopping centre (hoping for a cooler temperature) building a better house, e.g. making use of thermal mass or an appropriate window to wall ratio (long-term way of finding a cooler spot) emigrating

- letting the mind adjust so that it becomes used to warmer environments

34