using responsive building modeling to conceive ...

ÉC OLE PO LY TEC H NIQ U E FÉ DÉRALE D E LAUSAN NE

Proceedings of CISBAT 2011 International Conference 14-16 September 2011, EPFL, Lausanne, Switzerland CLEANTECH FOR SUSTAINABLE BUILDINGS – FROM NANO TO URBAN SCALE Copyright  2011 EPFL ISBN CD-version: 978-2-8399-0906-8 ISBN Print-version: Vol.I: 978-2-8399-0907-5 Vol.II: 978-2-8399-0918-1

Conference Host / Editor Solar Energy and Building Physics Laboratory (LESO-PB) Ecole Polytechnique Fédérale de Lausanne (EPFL) Station 18, CH - 1015 Lausanne / Switzerland [email protected] http://leso.epfl.ch Administration Barbara Smith, EPFL, Switzerland Scientific partners Cambridge University, UK Massachusetts Institute of Technology, USA IBPSA-CH, Switzerland Scientific committee Chairman: Prof. J.-L. Scartezzini, EPFL, Switzerland Members: Prof. Derek Clements-Croome, Reading Univ., UK Prof. Leon Glicksmann, MIT, USA Prof. Anne Grete Hestnes, NTNU, Norway Prof. Hansjürg Leibundgut, ETHZ, Switzerland Prof. Hans Martin Henning, FhG-ISE, Germany Dr. Nicolas Morel, EPFL, Switzerland Prof. Brian Norton, DIT, Ireland Prof. Christoph Reinhart, Harvard University, USA Dr. Darren Robinson, EPFL, Switzerland Christian Roecker, EPFL, Switzerland Prof. Claude Roulet, EPFL, Switzerland Dr. Andreas Schueler, EPFL, Switzerland Prof. Koen Steemers, Cambridge University, UK Dr. Jacques Teller, Univ. of Liège, Belgium With the support of Swiss Federal Office of Energy (SFOE) Ecole Polytechnique Fédérale de Lausanne (EPFL)

Members IBPSA Switzerland: Prof. Gerhard Zweifel, HSLU, Lucerne Prof. Thomas Afjei, FHNW, Muttenz Prof. Stéphane Citherlet, HES-SO Yverdon Dr. Darren Robinson, EPFL, Lausanne

Private sponsors Bank Julius Baer & Co Ltd, Switzerland Romande Energie SA, Switzerland

IBPSA-CH

Cambridge University

MIT

OVERCOMING THE ADDITIVE-INTEGRATIVE PARADOX: USING RESPONSIVE BUILDING MODELING TO CONCEIVE NEW APPROACHES TO THE INTEGRATED FAÇADE J. Ko1; L. Widder2 1, 2: Department of Architecture, Rhode Island School of Design; 2 College Street Providence, RI 02906 USA

ABSTRACT Integrated Design is defined by the multi-functionality of each architectural element and its capacity to serve structural, thermal, building physical and spatial mandates. For both engineers and architects, this degree of resolution has enormous intellectual appeal; for low-exergy approaches to the built environment, it means optimized performance. In practice, however, integrated design has meant a struggle to frame information appropriately so as to support the simultaneous resolution of structural, mechanical, building physical, fabricational and architectural problems. The quest for building systems and knowledge integration has often devolved into a series of add-ons chosen from market-available products. The increased focus on energy efficiency and human comfort has driven the development of many computational building envelope assessment software tools. Yet the promise of computational analysis to contribute significantly to a truly integrative, rather than additive, design process for the detailing architect is far from realized. This paper builds on the premise that the detail scale is well-suited to a truly integrative approach to building systems if it is paired with analytic software that gives early performance feedback to detail considerations. To gauge the appropriate range of values and to map the process of resolution for envelope design as a support to more appropriate collaborative software interface, this paper considers detailed wall sections at the juncture of wall and a window, assuming a low-exergy model of acclimatization. It also applies a similar approach to a “ground-up” study of envelope-integrated acclimatization in which building components respond symbiotically to technical and architectural requirements. This paper‟s contribution to the additive-integrative dilemma is two-fold: analytic, addressing the need to define the benchmarks and appropriate capacity for dynamism upon which relevant software in support of systems integration at the detail scale might be based; and creative, testing instances in which materials and design approaches both within and outside of the traditional repertoire of small-scale residential construction might realize better-integrated envelope systems. INTRODUCTION Integrated Design is defined by the multi-functionality of each architectural element and its capacity to serve structural, thermal, building physical and spatial mandates. For both engineers and architects, this degree of resolution has enormous intellectual appeal; for low-exergy approaches to the built environment, it is paramount to optimized performance. In practice, however, integrated design has meant a struggle to frame information appropriately so as to support the simultaneous resolution of structural, mechanical, building physical, fabricational and architectural problems. The January 2011 issue of Architect Magazine, the official publication of the American Institute of Architects, may be a bell weather of the status of integrated design as it is currently practiced in the US. It featured an article by Kiel Moe, entitled „Do More With

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Less: Double-glazing vs. masonry‟, in which his diagnosis of the double glazed curtain wall‟s “cascade of compensations” for its environmental inadequacies is predicated on the insight that “the linear model of progress in architecture is invariably additive. When architects encounter new problems and obligations, they often respond by layering materials, technologies, consultants, software.” The quest for building systems and knowledge integration has devolved into a series of add-ons: an “integrated” wall as an assembly of exterior shading devices, user-operable shades, multiple glazing layers, air gaps, cleaning mechanisms and other gadgets. The building envelope is a site for the integration of technologies, which advance human comfort while also supporting optimal building performance. The building envelope is also the locus of enormous effort and activity on the part of the architect as he or she negotiates these demands and translates a design idea into reality via the detailing process. The detailing process has generally been an empirical one, reliant on good practice, precedent study and ratiocination. While not inherently incorrect, this has proven increasingly inadequate to meet the current need for building envelope innovation. The increased focus on energy efficiency and human comfort has driven the development of many computational building envelope assessment software tools. Yet the promise of computational analysis to contribute significantly to a truly integrative, rather than additive, design process for the detailing architect is far from realized. In [2,3], a parametric approach to the detailing process is proposed, designed to bridge the gap between current practices and computational analysis at early stages of design detailing. This approach is captured by the following steps: 1. Benchmarking: In this initial step, typical cases of assemblies are identified as cases from which other versions can be derived. The criteria for benchmarking should consider best practice for thermal and building physical performance while architectural expression may be neutral or conventional. 2. Formulating the problem parametrically to facilitate subsequent iterations: Rules that govern the detailing decisions for these benchmark cases are extracted to create a framework for systematic variation. Positioning benchmarks as a part of a continuum typically requires a clear articulation of desired architectural expression, but also lightens the iterative process since considerable investment at this stage is placed on understanding relationships and anticipating potential trade-offs as a parameter is varied. 3. Establishing a dynamic link to existing computational tools: The analytical software appropriate to the particular focus of study is sought, its efficacy tested and recommendations for more interactive modes of operation shared. Applied to the parametric model, these computational tools are used to compare energy performance as parameters vary. An analysis at each iteration is used to refine the rules that govern the parametric formulation and as a basis to propose changes in detail strategy. This paper considers a case study of systems incorporation at the juncture of wall and a window, assuming a low-exergy model of acclimatization. It also applies a similar approach to a “ground-up” study of envelope-integrated acclimatization in which building components respond symbiotically to technical and architectural requirements.

CASE STUDY:

INTEGRATED HEAT EXCHANGERS FOR VENTILATION IN SOLID CONCRETE CONSTRUCTION

This approach can be demonstrated on a simplified design problem of incorporating a heat air exchanger in concrete wall construction with exterior insulation and rain screen. From an exergy standpoint, the choice of concrete wall construction offers an extensive, thermally stable wall surface for low temperature heating. From a low energy need and

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building physical standpoint, the exterior insulation and rain screen construction represent proven methods of mitigating thermal transmission and both ultraviolet and water-based degradation of the insulating layer. In a previous study, benchmark cases at the window were developed for typical locations of the window in the depth of such a wall construction [3]. To test the potential of the proposed parametric approach to envelope detailing for the promotion of systems integrated design, the problem here focuses on the location and detailing of a heat-pumpbased air exchanger (BS2‟s Airbox1) relative to localized thermal performance in the window-to-wall assembly as the window position moves in the depth of the wall. Based upon the manufacturer‟s recommendations for the installation of the heat recovery ventilation unit, benchmarks for this augmented problem were devised relative to the different opportunities afforded by the window location. In the construction details of the benchmarks in Fig 2, the location of a through-wall vent line is held constant, assuming a horizontal penetration below the windowsill behind the windscreen cladding.

Figure 2: Construction details and THERM analysis for heat recovery unit locations as window position varies; from left to right: interior flush; thermal neutral axis and exterior flush 1

See http://bs2.ch/de/products/airbox.php

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In the interior flush case, the ventilation line could be routed horizontally, as depicted, or vertically to emerge beneath the sill, both suggested positions given by the manufacturer. In keeping with architectural merits of the interior flush window, its capacity to emphasize the interior surface of the room as a continuous, unbroken plane, the logical installation point for the heat recovery unit would be a niche below the window, in front of which an access panel that could be installed in plane with the finish wall surface. When the window is located in the neutral axis (within the insulating layer), the use of a wood casing on the interior is used to conceal the insulation layer and the installation brackets which hold the window in place. It is logical to imagine the extension of that casing as a cover for the heat recovery unit, which could then be located adjacent to the wall inside the tempered space rather than requiring a niche in the wall. Such casework details are a commonplace feature in the location and integration of conventional radiators. For an exterior flush window installation, which in architectural terms would allow the full expression of the concrete wall as both finish surface and deep envelope. Since no casing is foreseen at the window and the continuity of the concrete surface would be undermined by an access panel as foreseen as in either of the two cases to be described below, the heat recovery unit is located in the floor slab, one of the installation solutions suggested by the manufacturer. Despite their substantial differences in appearance, this series of details represents a continuum as the parameter of window position varies. The advantage of conceiving of this problem parametrically is that it allows for comparative studies to be conducted at the early stages of the design detailing process during which a primary role is to support a detailing architect to distinguish competing alternatives, rather than to quantify absolute performance. The infrared color maps shown in Fig. 2 are appropriate for early stage evaluative response in the detailing process, and can be useful to draw initial conclusions that might affect detailing choices. Tradeoffs in architectural expression and thermal performance, for example, can be articulated in a way that would be difficult to do using empirical or typological approaches. For all cases, the vent line perforation distends the isotherms, showing far greater thermal transmissivity near the window aperture. The better thermal performance of the exterior flush window installation is negatively impacted directly at the site of the perforation and in the sill area. Some loss of thermal capacity results from the displacement of solid concrete in the wall surface by the conduit, and colder surface temperatures are indicated from the sill downward but the lower portion of the wall appears to perform fairly consistently along its length. The trade-off for better localized performance at the window is the much longer conduit run to the heat recovery unit located somewhere in the floor slab and the reduced accessibility of the floor-based unit. In comparison to the exterior flush case, the neutral axis case displays similar thermal impact at the perforation, which is amplified by the greater transmissivity in the sill area associated with this window location. Loss of thermal performance along the length of the wall is, on the other hand, mitigated by placing the heat recovery unit on the warm side of the concrete wall. This case demonstrates superior thermal performance based upon surface temperature at the interior plane of enclosure, the trade-off being the need for an ancillary enclosure around the heat recovery unit, which protrudes into the interior space. The extent to which this solution is actually necessary depends on the ingenuity of the architectural design and its capacity to understand the enclosure box as, for example, contributing to furnishing. At first glance, the interior flush case could be discounted at the outset because of its poor thermal performance; from the perspective of architectural design and expedient installation, however, the preservation of the continuous wall plane and the short conduit run and easy accessibility of the heat exchange unit, it is the most plausible of the three installations. The ability to be able to do a quick performance study at this early stage of

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design allows the detailing designer to anticipate conflicts that might arise despite an initial decision in favor of a construction strategy amenable to systems integration.

ALTERNATIVE PREMISES: SYSTEMS INTEGRATED DESIGN FROM THE GROUND UP Even with the simple example just discussed, it is clear that choices made at a building-wide scale about systems and assemblies cannot guarantee truly integrative approaches to thermal performance. In fact, if one adds the mandates of reusability/recyclability, lower material intensity and an envelope balance point approach which takes into account the human desire for certain fluctuations in interior climate (as in opening a window), this goal is only rarely achieved by the assembly of available building products outside of an additive mode of working. Ultimately, by identifying these requirements and testing their interplay at detail scale, it may be possible to conceive of new families of assemblies and components that account for perforations, wall depth, fasteners and finish surfaces on a specific, as-needed basis. This approach to building components would start from the exceptions – windows, doors, parapets – rather than the typical approach, in which the standard envelope assembly is given primacy. For illustrative purposes, we will consider the potentials of new families of materials relative to the demands of integrative design, for example, such high-strength, lightweight freely formable materials as natural fiber reinforced epoxy composites. Given their material and fabrication qualities, the means to address distributed building systems, structural capacity, low thermal transmissivity and architectural expression could be resolved in an integrated way rather than by the addition of components as the list of requirements grows. One example based upon the preceding exercise of locating a heat recovery ventilation system relative to a window appears in the speculative project for a thin wall house illustrated in Fig 3.

Figure 3: Study for a natural fiber reinforced low-rise house with integral structural, thermal, spatial and envelope considerations (Project: L.Widder, J.Ko, E.Nelson with J.Atkins, J.Honsa, T.Sheridan)

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Inherently water and air infiltration resistant fiber reinforced walls, crenellated at two different scales for local bending and lateral/gravitational loading, comprise a thin, light exterior wall given thermal resistance by vacuum insulation and UV protection by a shorter-lived rainscreen façade. At the windows, however, the material efficiency of the thin shell defers to a deep, hollow wall construction, which would facilitate the installation of heat recovery ventilation, accommodate deeper operable window components and can provide additional lateral stability [4]. At a detail scale, the material‟s formability is exploited to create fasteners and brackets with reduced thermal transmissivity; this limits building physical problems from thermal transmission and the combination of unlike materials. Without early-stage evaluation, the application of these new materials to the built environment is difficult to conceive at a detail scale. There can be no reliance on precedent or good practice, nor can manufacturer testing and specs be presumed. The prospect of working in a material in which any number of formal possibilities exist can much more productively translate into a collaborative, iterative process when quick, visually-couched feedback is available. Furthermore, the holistic development of a building assembly approach can model an integrative, rather than an additive, method of working which could be transposed to other assemblies. The transfer of emergent building materials and systems technologies to built environment implementation can be facilitated by the use of detail-scale feedback, accelerating industry uptake and leading the way out of the additive/integrative dilemma.

CONCLUSION Many valuable modeling and visualization tools already exist at site, building and systems scale to aid in the prediction and realization of the most intelligent resolution of the energy needs accruing to human habitation. By complimenting these scales of inquiry with responsive tools at detail scale, the basis for true symbiosis in systems integration can be accelerated. REFERENCES 1. Moe, Kiel „Do Less With More‟ in: Architect Magazine January 2011 (web-based edition, http://www.architectmagazine.com/high-performance-building/do-more-withless-lower-tech-higher-performance.aspx) 2. Ko, J. and Widder, L., Engineers/Architects: Defining Collaboration Bases for Improved Use of Parametric Software in Integrated Design, 2nd International Exergy, Life Cycle Assessment, and Sustainability Workshop & Symposium (ELCAS) Conference Proceedings, Nisyros, Greece, June, 2011, forthcoming. 3. Ko, J. and Widder, L., „Building Envelope Assessment Tool for Systems Integrated Design: Understanding and Using the Reciprocity Between Parametric Analysis and the Architectural Construction Detailing Process‟, Proceedings of PLEA 2011, Louvain-laNeuve, Belgium, July 2011, forthcoming. 4. Sauerbruch, M. and Hutton, L., www.sauerbruchhutton.de. A similar approach to double-glazed apertures has been used to good effect by, among others, Sauerbruch Hutton in their university buildings at Jessop West in Sheffield, England, and their office building Maciachini in Milan. See http://www.sauerbruchhutton.de/#projekte

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ACKNOWLEDGEMENTS

CISBAT 2011 would not have been possible without the efficient contribution of the secretariat of the Solar Energy and Building Physics Laboratory as well as that of our scientific and technical staff. Our scientific partners from Cambridge University and the Massachusetts Institute of Technology as well as the members of the international scientific committee and the session chairs have enthusiastically supported the conference and ensured its quality. We would like to express our sincere thanks for the time and effort they have spent to make it a success. CISBAT can only exist thanks to the financial support of the Swiss Federal Office of Energy. We are grateful for their continuing support. We also owe sincere thanks to the two private sponsors of this edition, Bank Julius Baer and Energie Romande, whose support was vital for the conference. Through their presence, they have not only allowed us to extend the programme, but have also shown their commitment for a more sustainable built environment. Finally, we cordially thank all speakers, authors and participants who have brought CISBAT 2011 to life.

Prof. Dr J.-L. Scartezzini Chairman of CISBAT 2011 Head of EPFL Solar Energy and Building Physics Laboratory