‘Healthy Buildings’: Toward understanding user interaction with the indoor environment

In recent years, research and the building industry have increasingly focused on issues regarding the lowering and optimising of operational energy use in buildings. This has resulted in several pilot projects illustrating how these can be achieved, e.g. Danish projects like ‘The Comfort Houses’ (some of the first Danish passive houses) ¹ and ‘Home for Life’ (active/zero energy houses). ² Besides exemplifying construction techniques and technical service systems as well as documenting energy use, the mentioned projects were evaluated according to the resulting indoor environment, qualitatively and quantitatively. The findings of ‘The Comfort Houses’ project ³ show challenges in fulfilling elements of the indoor environment, primarily due to problems with overheating during summer. The study also concludes that the design process needs to contain analysis of the indoor environment, besides the development of the design, to make sure the demands can be fulfilled. The research further concludes that there should be more focus on occupants’ lifestyle and behavioural traits when designing and planning passive and active systems, as the assumptions in many cases did not fit. In one case, for example, a family was concerned about their child’s safety if opening windows sufficiently to allow cooling and therefore chose not to do so, with overheating as a result. Hence, user-friendly solutions should be important considerations to allow the ‘correct’ operation of systems while also considering realistic user behaviour. ³ Similar findings appear in the research of ‘Home for life’. ⁴ Overall, the project concludes that 50% of the altered preconditions are due to factors in the building, control and technology, and 50% are due to the family’s behaviour that was at variance with the original estimations. ⁴ With regard to the passive house requirements, the main focus is on energy use. However, the passive house standard includes an overall demand for thermal comfort. ⁵ Nevertheless, this is analysed by using values of the monthly temperatures in the calculation method on the overall geometry of the building. An hour-by-hour dynamic simulation, or at least a simple check of the 24-hour maximum temperature for the critical rooms, would be a more reliable methodology to state the risks of overheating in the actual design. This methodology would also allow testing of different scenarios of user-behaviour and thereby test the robustness of the design. Unmistakably, the abovementioned research states that the user-behaviour and every day practices of the occupants are of major importance in the performance of the indoor environment – issues that are not sufficiently taken into account in today’s practices.

Along with the development of different low-energy and zero-energy concepts, voluntary sustainability certification schemes (BREEAM, LEED, DGNB) have been developed around the world – certification schemes that have a wider approach to sustainability than solely energy. However, the first-generation schemes still have a large focus on energy. ⁶ Recently, the Danish sustainability certification scheme, DGNB-DK, was developed taking its point of departure from the German DGNB certification scheme. The scheme is voluntary; however, increasing numbers of clients have requirements for sustainability and today very few buildings are built as certified passive houses in Denmark. Some of the first passive houses were built in 2008, and the last ones registered in the Passive House database were in 2013. ⁷ Today, the passive house’s standard seems to have been be outperformed by DGNB.

DGNB seems to appeal to many stakeholders in the Danish building industry. The certification scheme has a wider approach to sustainability and focuses on the whole life-cycle of the building while taking into account accessibility, flexibility, life cycle assessment and life cycle cost besides general issues like low-energy use and indoor environmental goals. If the popularity of DGNB keeps growing, the criteria within the assessment will have a significant influence on the built environment in future. The definition of a ‘healthy building’ in DGNB is mainly founded on an engineering approach based on European standards like, e.g. EN15251:2007 ‘Indoor Environmental Input Parameters for Design and Assessment of Energy Performance of Buildings Addressing Indoor Air Quality, Thermal Environment, Lighting and Acoustics’. However, is the question of aiming for ‘healthy buildings’ only a matter of the measurable indoor environment? Perhaps, certification schemes like DGNB result in limitations and could even, in as much as they may rely on a state of incomplete knowledge about how humans interact with the indoor environment, end up promoting unsatisfactory solutions. In research, there is a tendency to perceive the current evidence of how humans react to the indoor environment as adequate, although it might in fact be asymmetrical, as illustrated by the following example. On the website of the European Commission, an EU research project with the purpose of creating resource-efficient buildings with ‘healthy and comfortable indoor environments’ announces that ‘when inside, a person’s primary needs are ample amounts of daylight and fresh air as well as exposure to the right temperature’. ⁸ However, this reflects the current state of knowledge of indoor climate more than it reflects available knowledge of the interwoven physiological and psychological human needs.

New evidence is emerging that the design of spaces can have a comprehensive influence on the human physiology and psychology. Any living organism needs to adapt by counteracting changes in its environment in order to keep the inner biochemical stability needed to maintain the biological processes of life, a concept known in physiology as the homeostatic balance. ⁹ Although air quality, temperature and daylight are obviously important homeostatic parameters, they far from cover the complexity of the interplay of advanced organisms like humans with their environment. We are equipped with a number of interconnected systems to handle these additional processes, e.g. the immune system that takes care of our adaption to the microbiological challenges of the environment (see for example, the editorial by Bayer and Grimes in the December 2015 issue of Indoor and Built Environment ¹⁰ ). Another major system is the stress system. While no single accepted definition of stress exists^11,12 and stress has become a very broad term in popular conception, a relevant definition of stress as seen in a physiological perspective is that of Chrousos, Loriaux and Gold) ¹³ : The term ‘Stress’ describes a state of threatened ‘homeostasis’. In the cause of evolution, biological systems that have developed to defend the homeostatic balance have become ever more refined. Furthermore, they have developed to cope with actual threats as well as anticipated threats in order to avoid damage to the organism or e.g. disadvantageous social situations leading to unfavourable access to resources. Stress reactions can then be divided into two categories. Systemic stress constitutes a direct challenge to the system like blood loss, infection and pain. Lack of fresh air as well as exposure to the right temperature can be perceived as belonging to this class of stressors. Psychogenic stress on the other hand constitutes an anticipated threat. ¹⁷ While a systemic stress reaction largely will be based on controlled reflexes, psychogenic stress reactions demand a complex appraisal procedure, which is carried out on a non-conscious level, mainly by structures in the brain’s so-called limbic system. ¹⁴ The stress reaction itself will consist of activation of bodies’ two major overlapping stress systems – the sympathetic nervous system which is a subdivision of the autonomous nervous system – and the so-called hypothalamic–pituitary–adrenal (HPA) axis. Unlike the autonomous nervous system, the HPA axis is an endocrine system, generating as its end product the hormones called corticoids, of which the human variant is called cortisol. The activation of these two systems in the case of psychogenic stress releases energy resources and shuts down temporary unnecessary processes in order to release energy for a so-called fight-or-flight behaviour. While the activation of the autonomous nervous system is short termed, cortisol can exert a longer lasting influence and, if the condition becomes chronic, be directly damaging to the organism. The majority of the cells in the body have receptors for cortisol and, among the mechanisms controlled by this hormone, are the immune system and digestion, by way of insulin levels.^15,16 Also cognitive systems are largely influenced by cortisol, as there are a large number of cortisol receptors in areas of the brain harbouring the structures computing working memory, emotional memory and especially declarative memory. ¹⁷ Of particular interest for the indoor environment, recent research indicates that whether a space in which one encounters acute psychogenic stress is closed, or possesses openings allowing the potential for flight, significantly influences the resulting level of cortisol. ¹⁸ Due to the comprehensive effect of cortisol on well-being as well as a number of key physiological and cognitive functions, the spatial configuration of a space might have a substantial impact. As is apparent from the above, while the emphasis on energy efficiency puts an emphasis on the distribution, size, form and placement of openings in the façades due to the consequences for gaining or losing heat, these other consequences for the well-being of the users of the building must not be overlooked. Furthermore, recent research within the branch of neuroscience called neuroaesthetics reveals that different types of spatial configurations of spaces cause distinct reactions linked to well-being within the brain. Thus, functional magnetic resonance imaging suggests that curvilinear spaces are significantly more likely to be judged as pleasant, and spaces with curvilinear contours are more likely to activate brain structures responsible for reward and the emotional salience of objects. Rooms with a larger ceiling height activate visuo-spatial structures responsible for exploration and attention and are more likely to be judged as beautiful.^19,20

Evidently, a huge asymmetry in our knowledge exists, on the one hand regarding ways in which humans react, both in terms of physiology and in terms of psychology and behaviour in the indoor environment, areas about which our knowledge is limited, and on the other hand, knowledge about human reactions to the indoor climate, which are very well investigated. In as much as certification systems and building codes only reflect current knowledge, this might actually, due to this asymmetry, leading to loss of quality of the indoor environment and well-being for the users, as important aspects of human interaction with the indoor environment will be overlooked or only poorly represented. Instead of improving and guaranteeing quality as intended, the result might be the opposite and even, as exemplified above, dysfunctional. As requirements for knowledge-based building designs rise in step with increasing demands for buildings, driven by demands for energy efficiency and lowered CO₂ footprints, it is important that thorough knowledge be obtained on all aspects of user behaviour, including the impact of the indoor environment on the users’ psychological as well as physiological well-being, on a somewhat more complete level. This fact is putting pressure on the research community to keep pace with recent rapid developments.