Contemporary Passive Shelters | Environmental Diversity and Contemporary Lifestyles
Currently, buildings use large amounts of their operational energy to counteract the impact of the external environment on their inhabitants. Recent years have seen a progressive attention on these themes due to the great energy saving potential of the sector, moving towards an integrated design approach between the building and its plants. Nevertheless buildings, although more efficient, are still conceived as containers of mechanically controlled microclimates. However, today, technology and new theories of comfort allow a radical rethinking of how buildings are conceived, designed and inhabited.
This paper reports on a design research that investigates alternative models of habitable environments, proposing an original concept and role for buildings. The research aims to contribute to the discourse on new highly efficient buildings showing how an innovative design process based on the integration of adaptive comfort theory, building physics and thermodynamic principles, passive strategies and centrality of the user, can not only deliver less energy intensive and more comfortable buildings but also enhance the generative potentials of new forms and spaces towards a more contemporary and sustainable built environment.
Nowadays the necessity to reduce the energy consumption of buildings must start from a reduction of their energy demand. Various studies have agreed that the percentage of energy for comfort in buildings represents about the 60% of their operational energy (Cullen & Allwood, 2010). This huge figure is partially due to the poor efficiency of buildings’ systems and envelopes but also to a misleading approach to the design and use of the indoor environment. The adoption of the adaptive comfort theory by international directives (e.g. EN and ASHRAE) is one of the most ground-breaking ‘innovations’ in the field of sustainability. In fact, it allows the use of bioclimatic strategies in buildings, reducing their energy demand, and it also pushes designers to re-think the role of buildings in relation to the climate, the outdoor and indoor environments and their inhabitants. Yet the application of the adaptive theory is not yet widely taken up and its design potential not fully explored. This research investigates a generative design process that applies this ‘innovative’ theory to a residential passive unit in Tuscany, Italy, and it shows the architectural implication and potentials of conceiving buildings as part of the system surrounding-building-user.
- Research objectives
The classic theory of comfort is based on the thermal neutrality between the body and the environment and defines comfort as a standard, universal and uniform set of conditions. In energy terms, its extensive application to the design of indoor environments has resulted in the majority of global energy use employed to reduce the impact of the natural environment and its varying climate on us (N. Baker, 2001). Additionally, in architectural terms, the provision of comfort has become a mere technical issue, undermining the centrality of the users’ experience and their perception of the indoor environment in the design process. As a consequence the design of buildings and their environmental control has been separated in favor to an extensive use of mechanical systems. Also when the two elements are integrated into a process, buildings become stand alone entities separated from the surrounding and users become passive recipient of the mechanically controlled indoor environment.
Recently, field studies have demonstrated that people are comfortable in environmental settings different from those -narrow and constant- prescribed by the body heat balance (Brager, de Dear, 2003) These studies demonstrated the correlation between users’ environmental preferences and outdoor conditions and consequently they question the need for the extensive use of mechanical systems allowing the integration of passive strategies for environmental control. This integration changes the role of the building and its spaces in relation to comfort: a passive building, in fact, works as a system in its wholeness together with user and surrounding microclimate in order to dynamically mitigate and control the energy exchanges between the highly variable condition of the system (e.g. changes in occupancy pattern and internal heat gain) and of the surrounding (weather). This system has to passively and dynamically maintain not a fixed constant environment as aimed by the traditional notion of comfort, but rather the variability of indoor conditions within a certain range, as the adaptive comfort model suggests.
Spatial diversity, where users can move freely to find their preferred environmental conditions, becomes a key element of passive design: “when people are free to choose their location, it helps if there is plenty of usable thermal [and visual] variety. Then they can choose places they like, which are suitable for the activity in which they wish to engage”, Humphreys (1997).
How this spatial diversity can be first generated through passive strategies and consequently how the user interacts with it, become a design challenge of broad interest that this research tries to investigate for a residential unit.
- Design process
The new role of buildings was the occasion to investigate contemporary and projected way of living the built environment. It has been noticed that, due to the advances in the technology that permeates our lives, contemporary residential spaces do not reflect the changed lifestyles. Most people live buildings whose layout is still based on the traditional division in functional rooms that was driven by limitations in structural, environmental and technological systems and by a more rigid societal structure. If in the past rooms have assumed specific functions based on activities that could have been carried out only in those rooms, today these functions are losing their centrality due to the development of technology that has become extra-movable, light and multitasking (e.g. laptops, tablets etc.) allowing activity to be performed almost everywhere. In this case these reflections were applied to a residential space: contemporary and projected homes should provide a free and integrated space where different activity can be carried out according to different level of privacy, visual and physical contact.
3.1 Change of perspective
Preliminary studies and analysis on climate, comfort and site investigated the building as a passive system and showed that: 1. the principal views are towards the north -where there are hills and a natural park; 2. a south orientation to maximize passive solar gains is needed in winter; 3. a modulation of the energy flows during warm winter days and mid seasons is requested to avoid overheating; 4. the unit must be protected from direct solar gains in summer.
In order to gather these requirements together with the previous considerations about new living environments, adaptive comfort and spatial diversity, the concept of 'change of perspective' was developed. The concept's name recalls the changes in mindset that should be made when designing contemporary sustainable buildings but also the emotional complexity that the unit will provide in this specific case by modulating the energy flows in order to balance the equation between heat losses (conduction and ventilation) and heat gains (internal and external). Doing so, the perspective on and from the inside space will dynamically change during the days and seasons (Fig.2).
3.2 Performance analysis: the passive unit
The described concept has been then developed and tested adopting an evidence based approach and creating a constant dialogue between design and performance analysis (performed through specialist software such as dynamic thermal modelling and simulation, EDSL TAS, and daylighting software, Radiance). This methods was used to refine the bioclimatic strategies set in the preliminary analysis, to define the building's geometry and properties and to generate the spatial diversity within the unit.
Different unit's configurations, geometry and materiality were tested and integrated with architectural considerations in order to satisfy the comfort requirements and the inputs from the 'change of perspective' concept.
The spatial diversity was obtained along the height of the unit based on the thermodynamic principle that warmer air raises and tend to stratifies. But, in order to enhance this diversity, also for the daylight, the geometry of the openings, insulation and thermal mass were distributed according to the simulation’s results. Maintaining the building heat transfer coefficient constant, the insulation was increased at the top and reduced at the bottom to reduce heat dissipations in the warmer part of the unit and increase radiant temperature; larger windows and higher thermal mass were placed on the higher level and smaller windows in the lower level both on the south and north façade in order to enhance the gradient of temperatures and light within the unit.
The outputs from the performance analysis became the inputs for the architectural design:
as an example of the system/unit mechanism, during normal winter days all the shutters are open on the south façade while they are kept close on the north windows to reduce the heat losses and maximize the solar gains while during warm winter days those shutters partially cover the south facing windows to reduce the solar gain and partially open the north windows to increase the heat losses and allow the view towards the north.
3.3 Architectural Concept and Design.
The unit’s structure is made of prefabricated wood arches to which mezzanine floors are cantilevered. The internal layout consists of a peripheral distribution that connects four mezzanines and the ground floor where different activities can happen at the same time thanks to smart furniture, innovative appliances or current technology. The envelope is made of prefab insulated and thermally massed panels and on the same axis of the insulation the glass is attached to avoid thermal bridges. The mezzanines can be separated by the rest of the space using technical insulated curtains in order to provide privacy on request. The storage spaces are integrated in the vertical distribution and on the south and north side the ‘bridges’ are completed by the multifunctional net that can be used in different way according to the activity (Fig.3).
The curved shape of the unit (Fig. 1) has been designed to recall that of the arched sheds of the former warehouse that stands on the site and the surrounding hills while at the same time it allows the insulated stripes of the sliding skin to move on its surface and modulate simultaneously the heat gains and
heat losses through the envelop as described in the previous paragraphs generating the change of perspective showed in Fig. 4.
- Living the diversity
The design outcome provides diverse environmental combinations of light, temperature, privacy and views. Occupants can then choose the environmental conditions they prefer, following indoor migration patterns, ranging from close visual and acoustic contact with other spaces to high levels of privacy. The user personalizes the spaces, giving them temporarily the function related to the activity carried out. The richness and complexity of the user’s experience within this space, enriched by thermal and daylight diversity, has been visualised supposing possible patterns during typical days (Fig 5).
In a normal winter day in order to maximise passive solar gains and minimise heat losses, the sliding skin is set on the north facade. Views are all to the south and the unit provides all the range of temperatures included in the adaptive comfort band as well as different qualities of direct and indirect daylight due to the distribution of the south transparent elements. Users can then migrate within the space according to their preference as exemplified by the red and blue arrows in Fig. 5. At night the shutters cover the higher part of the unit in order to maintain the gradient of temperatures also at night. During warmer winter days the shutter partially traslate on the south facade to modulate the solar gains and increase the heat losses from the northern glased elements maintaining the unit within comfort and discovering the north views. Due to this strategy, the quality of the light changes as well providing a different perception of the same unit. In summer the unit has to be protected form the solar gains, consequentely in the early and late hours of the day the sliding skin protects the northern facade while in the central hours of the day it does if for the south facade. In this way, the night ventilation strategies are maximised and it is possible to maintain the unit in comfort for the whole summer. Fig. 4 and Fig 5 show the effect of the adopted strategies for the passive unit and the possible migration pattern of the users within the unit.
The paper reports on the generative process followed to design a contemporary unit that provides the range of thermal and visual adaptive comfort throughout the year by passive means extending the user’s enjoyment of the space and reducing the energy demand for comfort. This research offers hints for reflection on the contemporary way of conceiving sustainable buildings based on an integrated process that leads to the building-plants systems, claiming that today’s technology, simulations and the technological state of the art allow architects to make a further steps towards innovative sustainable buildings: in fact it is possible to design buildings that work in synergy with the surrounding and the user in order to offer more sustainable, comfortable and contemporary environments (Schiano-Phan, Weber, Santamouris, 2015). The outcome of this research, yet experimental, can be applied to different typologies of buildings in order to really make a shift in the way buildings are conceived, built and lived towards more sustainable built environment and users. In fact, studies suggest that changes in the built environment can strongly influence behavioural choices (Wilhite, 2009) and this correlation, if exploited, can potentially minimise one of the main barriers towards building sustainability that is the cultural and behavioural barrier.
The Authors acknowledge the Master of Architecture in Sustainable Environmental Design at the Architectural Association, London, where the research ideas were developed.
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