Sep 26, 1999 - approach as follows, at least for the North American scene: ... interior elements from one functional specification to another, within the same.
Sustainable Development and Open Building Presentation to CIB TG26 Brighton UK, September 26, 1999 Nils K. Larsson CETC, Natural Resources Canada
A.
A Working Definition of Sustainable Development
Building researchers and designers who care about the environment find themselves increasingly part of the broader "Sustainable Development" (SD) movement. It has therefore become of critical importance for the research community to understand how the principles of SD can be applied to the building sector. The best place to start is with the broader and more generic statements: …development that meets the needs of the present without compromising that ability of future generations to meet their own needs 1; …improving the quality of human life while living within the carrying capacity of supporting ecosystems 2; … the provision of permanent prosperity within the biophysical constraints of the real world in a way that is fair and equitable to all humanity, to other species, and to future generations 3 Although a significant proportion of the building research and design community now includes consideration of SD in their work agendas, there is a surprising lack of consensus on the more specific factors that should be considered. For example, Ian Cooper, a well-known research architect in the UK4, surveys the design profession using four main areas in his definition: the physical environment, futurity, social equity and participation. On the other hand, others would insist on economics as being a prime factor. Some cynics insist that SD has become popular in government circles precisely because of the inclusion of the "economic sustainability" component, which allows expensive measures to support ecological systems to be dispensed with on economic grounds. Regardless of the breadth of definition of SD, a problem remains with its scale of application. The concept was developed and originally applied to broad social
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issues, at a national or regional level. However, many researchers and policy makers are now applying it to the level of building design and construction and one may legitimately question whether social equity has much meaning at the level of an individual building. However, the character of the building stock as a whole, or in a city, obviously has immense social impact. A working definition is needed for this paper, and the author takes the position that the meaningful issues at stake for the building sector within SD should include the following considerations:
The continuing viability of natural ecological systems, including reduced
consumption of scarce resources, reduced ecological loadings, and a healthy and stimulating interior environment. Social equity, related primarily to reduced negative impacts on adjacent properties, affordability, social integration and respect for cultural context. Economic constraints, relating to life-cycle costs for the owner and, again, affordability. This is close to the definition established in CIB's forthcoming Agenda 21 on Sustainable Construction 5 We can define this in even more detail, by adapting the assessment framework developed through the Green Building Challenge project6. The main sections within this framework consist of the following: Resource Consumption Ecological Loadings Secondary Loadings Quality of Indoor Environment Economics Functionality Management This will be used as a checklist, against which the actual or anticipated characteristics of Open Building and Conventional building approaches will be assessed.
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B.
Open Building
The Open Building approach was developed by J. Habraaken7 in the 1960's, primarily in response to problems in adapting Dutch housing to changing demographic needs of residents. Open Building is both a philosophy and a technical approach. In this paper we will focus primarily on the latter and how it might relate to Sustainable Development (SD) issues. An open building consists, in OB parlance, of two primary types of components: Support and Infill. The concept is easy to understand for those who are familiar with office buildings, since the distinction of Base Building and Tenant Fit-Up has evolved without the benefit of a philosophy in that sector. This has been a natural response to financing mechanisms and the uncertainties of speculative leasing, and is very close to the principles of OB. The OB approach allows a separation to be made between large-scale and longlived base-building structures (Support) and the more varied and shorter-lived systems and facilities contained within it (Infill). The large and permanent structure is custom-designed for the site, while shorter-lived internal systems are manufactured off-site to modular dimensions and installed as a quite separate operation. Issues related to changes of building use This approach offers another distinct advantage, in that it offers the possibility of greatly extending the life-span of buildings, by facilitating functional changes within the base building without requiring major renovations. This has a clearly beneficial effect in the reduction of future need for new construction materials, and in the disposal of construction and demolition wastes. Such an approach may also enhance the long-term value of the asset for the owner. In both the office and the residential sectors, as a more theoretical measure to improve the flexibility and adaptability of housing, the underlying concept has the potential to significantly advance the agenda for environmental performance. OB can create a class of buildings with an extremely long life span because of a greatly increased level of flexibility and adaptability, and the advantages of this are significant. To clarify this point, it should be recalled that conventional buildings are designed to satisfy a single functional purpose and to do so in a relatively specific way. Thus, the configuration of floor plates (width and length), bay sizes, floor heights, floor loading assumptions, fenestration patterns and sizes and mechanical systems, are all designed to suit the specialized needs of offices, residential, retail, or other specific purpose. The degree of specialization of specific building types has increased during the last 50 years, with many good results.
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There are, however, also some marked disadvantages to the conventional approach. Functional requirements within a specific building type change over the years, and the more specialized the design, the more difficult it is to adapt to these changing requirements without resorting to "gut rehab". For example, the rigidity of apartment building design usually makes it extremely difficult to change unit layouts or sizes to reflect changing demand. A glut on the office building market makes it desirable to be able to convert to residential or hotel uses, and a downturn in the retail market may make it desirable to convert to office space. Although there are many recent examples of successful conversions of 1960's and 1970's office buildings to residential uses, this is more the exception than the rule. We are not aware of any successful conversion of a post-war apartment building to office uses, although a good number have been converted to apartment-hotels. The need for convertibility is always present: even during the depth of the commercial building recession in Toronto during the early 1990's, several existing warehouse facilities were torn down and replaced by new facilities with higher ceilings. It should be noted that, as operating energy is reduced through better design and operation, embodied energy will become of increasing concern. A longer life span for the basic elements is therefore likely to become a public policy issue. The objection to developing a more general-purpose building type is that the developer is forced to pay extra to build in the flexibility to allow for future changes. In some cases this is true, but there are some compensating advantages. If we take, for example, the case of building residential apartment buildings to OB standards, we can summarize the required changes in design approach as follows, at least for the North American scene:
Floor plate increased from typical 21 m to about 25 m, to permit more efficient office uses in case of conversion; Structural bay spacing set at about 9 or 10 m, again for future office flexibility; Floor-to-floor height increased from about 2.9 m to about 3.35 m; Careful placement of core and vertical services.
The first three of these undoubtedly cost more, but the asset value of the building should reflect the easier future conversion to hotel or office uses. Further, a deeper floor plate will provide more interior storage space in the current function of apartments, and this is a notorious deficiency of multi-unit residential buildings. Issues related to changes within a building use A second major advantage of an OB approach is the increased ability to modify interior elements from one functional specification to another, within the same building use, for an speedier and lower-cost response to changed functional,
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market or social requirements. We are used to seeing this in office buildings, as with the replacement of one lighting or partitioning system with another. Dimensional coordination makes such changes relatively rapid and low-cost. In residential buildings, however, this approach has only been implemented in a relatively small number of buildings in the Netherlands. Although the production of some 2000 housing units over 30 years is very modest, it has been sufficient to prove the advantages of the approach in terms of the speed and reduced cost of renovations, and the ability of buildings to adapt to changes in household composition. Why has the OB approach not been more widely used in the residential sector? Beyond the normal factors of a high degree of conservatism in the building industry, it is likely that a classic chicken-and-egg situation provides the largest barrier: a larger number of OB buildings are not designed because of the lack of widely available and economic fit-up or infill components; and large-scale production of such components has not taken place because of the few OB buildings with appropriate interior dimensional characteristics. The ability to more easily modify the interior elements of an OB comes about through the use of dimensional coordination (standard and scalable interior dimensions). Office buildings are designed in this way as a matter of routine, often with 1500mm planning modules and structural bay sizes of 7.5 or up to 12 m. Stephen Kendall, one of its foremost North American proponents, has pointed out two examples of benefits deriving from this approach8:
Conventionally constructed base buildings need not predetermine interior
layouts. By employing fit-out technology, building interiors can be upgraded to suit individual occupants without disturbing other occupants. (for example: advanced interior fit-out technology by Steelcase, Interface AR and other large companies in North America using raised cable management floors and systems furniture) Building subsystems are being developed in which certain assemblies such as facades, electrical and data systems, or heating systems, - even from competitive providers - can be installed or replaced without requiring the disposal of the entire system (for example: The ABSIC project at Carnegie Mellon University in Pittsburgh, Pennsylvania; studies at the OBOM Research Group at TU Delft point to the possibilities). Only OB theorists and a few practitioners have applied such an approach to housing, but the potential benefits from the industrialization and mass production of interior fit-up components are immense. In the residential case, it is not difficult to envision apartment buildings with a large variety of plans and gross areas, all providing interior spaces that are dimensionally coordinated along two axes.
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Mass production of standardized fit-up elements The widespread application of OB principles to housing has the potential of opening up of a vast market for interior fit-up elements for the residential market, including standardized partitions, storage facilities, floor elements, kitchen and bathroom fittings and service systems (such as flexible water supply and waste). The development of an industry to serve such a market could be an engine of economic growth, while resulting in reduced costs and higher quality. The chicken-and-egg problem outlined in the previous section could be broken in countries such as China, where an enormous amount of housing needs to be built in a relatively short time, and where manufacturers of dimensionally nonstandard interior components have not yet established a dominating position in the marketplace. In such an environment, a large-scale manufacturer of housing fit-up elements working to standard interior dimensions established in a largescale program of housing production, could provide interior elements of a superior quality and considerably reduced costs. Western architects might instinctively recoil from such a prospect, but housing designs with standardized interior dimensional coordination need not resemble Soviet or Chinese housing from the era of central planning. There is certainly no lack of variety and style in Western office buildings, and their designers follow the same precepts: feel free to plan non-standard spaces in lobbies and special function areas, but maintain dimensional coordination in the 85%+ of space that serves the standard office function.
C. OB meets SD Given that the background of Open Building and Sustainable Development are both interesting, in very different ways what, if any, is the relationship between the two? In assessing the potential of OB to play a positive role in moving towards sustainable development, we use the GBC framework cited in the first section as a checklist. C1
Resource Consumption
This performance concern consists of the following parameters: Resource Consumption Net consumption of non-renewable energy Net consumption of biologically productive land Net consumption of potable water Net consumption of materials
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There is no reason to believe that the OB approach will result in substantially different levels of consumption of land or water. Energy and materials is a different matter, however. Given that the GBC framework contains separate assessment dimensions for both ecological impacts and costs, there is actually little concern for the consumption of renewable resources; only the use of non-renewable resources concern us here. Thus, a high level of consumption of energy from a renewable source would be an issue only in terms of its cost or emissions. As energy is usually produced from a mix of renewable and non-renewable sources, energy consumption is therefore a relevant issue. In terms of operating energy, it is assumed that there is no validity in assuming that OB buildings would perform better then conventional ones. For embodied and recurring energy, on the other hand, it is clear that substantial differences exist, and this also brings in a link with materials consumption. In this regard, it is instructive to review a study carried out for the Athena Institute for Sustainable Materials9, and a later study on demolition energy10 carried out by others, also for Athena. Using the Athena software, the embodied energy of generic building designs was compared with various assumed service lives and levels of operating energy. The study focused on structural and building envelope systems with related interior finishes for an assumed 4,620 sq.m. threestorey office building in two locations. Embodied energy used for construction and periodic replacement was related to varying levels of operating energy values over different life spans with three different types of structure. For the purposes of this paper we are using only the concrete-based structure since, in fact, the overall life-cycle energy was similar in all three cases. Table 1 : Life-Cycle Energy Use v. Assumed Longevity
25 years 50 years 100 years
Initial Embodied gJ/m2
Replacement gJ/m2
Operating gJ/m2
Demolition gJ/m2
Total gJ/m2
4.93 4.93 4.93
2.56 6.47 15.12
44.03 88.05 176.10
0.120 0.120 0.120
51.63 99.57 196.27
(Toronto location, 3 Storeys + underground garage, concrete construction)
Table 2: Amortized Life-Cycle Energy Use, Annualized Basis v. Assumed Longevity
25 years 50 years 100 years
Initial Embodied gJ/m2
Replacement gJ/m2
Operating gJ/m2
Demolition gJ/m2
Total gJ/m2
0.197 0.099 0.049
0.102 0.129 0.150
1.76 1.76 1.76
0.005 0.002 0.001
2.065 1.992 1.961
(Toronto location, 3 Storeys + underground garage, conc. construction; demolition at 25, or 50 or 100 years)
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Table 3: Amortized Life-Cycle Energy Use, Annualized Basis v. Assumed Longevity, High-Performance Building Basis
25 years 50 years 100 years
Initial Embodied gJ/m2
Replacement gJ/m2
Operating gJ/m2
Demolition gJ/m2
Total gJ/m2
0.197 0.099 0.049
0.051 0.065 0.075
0.880 0.880 0.880
0.000 0.000 0.001
1.128 1.044 1.005
(Toronto location, 3 Storeys + underground garage, concrete construction; demolition at 100 years, replacement energy reduced by 50%)
The Athena study assumed that the structure would be retained, even in the 100year scenario. This is in fact an unrealistic scenario for most situations. If we assume another scenario for which there is some evidence, that many buildings are demolished with their structures at the end of their service lives, then a different picture would emerge. In addition, there is some evidence that life spans of conventional buildings may be shorter than usually assumed in some areas or circumstances. For example, a field survey undertaken by Tomonari Yashiro on the life span of office buildings in Japan in 199211 showed that the life spans of both steel and concrete buildings were only about 30 years during the 1980's. A simulation of the amount of waste showed that an enormous amount of waste is produced by this phenomenon and that it will present serious disposal problems. Most demolition was ascribed to changing user requirements and tax incentives rather than a lack of physical durability. If we assume that the values in Table 3 might more reasonably be ascribed to buildings that are flexible enough to adapt to a variety of new functions over their life spans, then we need to compare these results with the values that would result from an assumption of demolishing the structure of a conventional or specialized building every 50 years. Over the 100 years, this would result in higher embodied energy (two buildings), plus the demolition energy of the first, with recurring and operating energy remaining the same. The results are shown in Table 4. Table 4: Amortized Life-Cycle Energy Use, Annualized Basis v. Assumed Longevity, High-Performance but Specialized Building
25 years 50 years 100 years
Initial Embodied gJ/m2
Replacement gJ/m2
Operating gJ/m2
Demolition gJ/m2
Total gJ/m2
0.197 0.099 0.148
0.102 0.129 0.150
0.880 0.880 0.880
0.000 0.000 0.002
1.179 1.108 1.180
(Toronto location, 3 Storeys + underground garage, concrete construction; assumes replacement of entire building every 50 years)
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These results show that there is a significant reduction in the total life-cycle energy over a 100-year period. Table 3, the Open Building scenario (structure life 100 years, recurring energy reduced by half because of design for disassembly and re-use) shows an annualized total figure of 1.005 GJ/m2, compared to 1.180 GJ/m2 for the more conventional and specialized scenario. Even with the same operating energy, the difference is about 15%, substantial but not overwhelming. C2
Ecological Loadings
The performance parameters of concern within this issue consist of the following: Ecological Loadings Emission of greenhouse gases Emission of ozone-depleting substances Emission of gases leading to acidification Given that operating energy is assumed to be the same for the OB and conventional cases, it is the emissions due to embodied and recurring production energy that is relevant, and the same value of about 15% reduction for the OB case appears to be a legitimate forecast. C3
Secondary Loadings
Secondary loadings include building outputs leading to ecological impacts which are of a second order of concern, as well as non-ecological effects, such as impacts on adjacent properties. The full list includes: Secondary Loadings Solid wastes Liquid wastes Thermal emissions Impacts on Site and Adjacent Properties Minimization of Transportation Impacts It is best to first dispense with those impact categories that are not relevant to the analysis. There is no reason to believe that Liquid Wastes, Thermal Emissions or Minimization of Transportation Impacts would differ in either case. However, a reduction in Solid Waste over the lifecycle could certainly be attributed to the OB approach, since it requires a high degree of inter-operability of internal components, and this reduces waste and increases the potential for re-use and recycling. Further, the long-lived structure made possible by the OB approach reduces demolition waste, and the reduction in embodied energy in
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Tables 1 through 4 is applicable, with an estimated 15% reduction possible over the lifecycle. Finally, considering Impacts on Site and Adjacent Properties, it is clear that an OB building that results in less demolition and quicker interior refits, will result in less disruption to adjacent owners and the public, although the extent of this cannot be estimated in an objective way. C4
Quality of Indoor Environment
This performance concern includes the following categories: Quality of Indoor Environment Air Quality and Ventilation Thermal Comfort Daylighting, Illumination and Visual Access Noise and Acoustics There is no obvious differentiation between the OB and conventional case in these areas of performance. C5
Economics
This issue area covers costs and economics for both the building and the broader society. Economics Life-Cycle Cost of Building Changes in Economic Value Broader economic impact A building that is adaptable to new uses will face a small cost premium, because of the use of more adaptable systems, such as floor plate layouts, structural bay spacing and greater (in the case of residential) floor-to-floor heights. However, this can be amortized over a very long period in an adaptable building. While the OB building faces some initial surcharges, it should be quicker to fill, because of the standardization of interior elements. A conventional building faces worse problems over time: a market shift that results in tenants moving out means that the building has to be renovated and is likely to be empty for many months, a significant loss of income to the owner. Thus, while the asset value of an OB building is likely to increase, an investor must take into account the probable future economic loss from the rigidity of uses in a conventional building.
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The most significant impact of OB, but one that is impossible to forecast with any certainty, is the economic benefit of mass production of standardized and interchangeable interior fit-up components for residential applications. This is likely to face resistance in North America and Europe, where existing manufacturers of non-standardized components are well entrenched, and where the retooling costs would well exceed immediate economic benefits. However, in developing countries with newly established or rapidly expanding building sectors there is a major opportunity for a growth industry. Turning to broader economic issues, the impact is mainly at the urban level. All current urban planning theory places a high value on mixed uses and higher densities, but the rapidly changing economic conditions in most cities means that today's prediction of an appropriate mix is likely to be proven wrong in a few years. There is therefore a great need for a more adaptable building stock, one that can quickly adjust to new urban growth patterns without causing local social and economic disruption. C6
Functionality
Although not strictly an SD issue, functionality issues have secondary impacts on the environment, the occupants, society and economics. The specific issues developed in GBC include: Functionality Flexibility and Adaptability Maintenance of Performance Controllability of Systems The issue area of Flexibility and Adaptability is, of course, where the OB approach is outstandingly superior to conventional design. The exact economic and productivity benefit to be gained from this still remains to be identified, and will presumably require a number of case studies. The other two performance categories are not relevant for this analysis. C7
Management
The set of issues include the following considerations: Management Construction Process Planning Performance Tuning Building Operations Planning Transportation Management Planning
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The parameter of most interest here are Construction Process Planning and Building Operations Planning. The construction process for the base building of an OB project needs to be no different than a conventional one, but it is in the interior fit-up elements that there are prospects of significant gains. The discipline of dimensional coordination and modular fit-up elements would, if implemented, create very substantial savings in time of installation, rate of defects and cost. With respect to Building Operations Planning, there are interesting prospects. A base building that is designed to easily accommodate a variety of future functions could be pre-approved for zoning flexibility. This could have a significant impact on the ease of management in rental buildings and would also have secondary impacts on profitability and asset value. D.
Conclusions
It is very difficult to make an accurate assessment of the environmental performance of a system that does not yet exist on a wide scale. However, certain predictions can be made with some certainty, and these show that there are many areas where the OB approach is likely to provide better performance than the conventional design and construction process. None of these are dramatic, but taken together, they make an impressive set: Resource Consumption Net consumption of non-renewable energy Net consumption of materials Ecological Loadings Emission of greenhouse gases Emission of ozone-depleting substances Secondary Loadings Solid wastes Impacts on Site and Adjacent Properties Economics Life-Cycle Cost of Building Changes in Economic Value Broader economic impact Functionality Flexibility and Adaptability Management Construction Process Planning Building Operations Planning In summary, there are many reasons of moderate importance why work on Open Buildings should be expanded and speeded up.
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End Notes 1. Our Common Future (Brundtland Report), World Council on Economic Development, 1997 2. Caring for the Earth, IUCN/UNEP, 1991 3. Costanza, Robert, John Cumberland, Herman Daly, Robert Goodland, Richard Norgaard. 1997. An Introduction to Ecological Economics. Boca Raton, Florida; St Lucie Press and International Society for Ecological Economics. 275 pp. 4. Cooper, Ian; Which focus for building assessment methods - environmental performance or sustainability?; in Building Research & Information, Vol. 27, No. 4/5, July-October 1999. 5. Bourdeau, Luc, Editor; Agenda 21 on Sustainable Construction (draft 3); Conseil International du Batiment, to be published Fall of 1999. 6. Cole, Raymond J. and Larsson, Nils; GBC '98 and GBTool: background; in Building Research & Information, Vol. 27, No. 4/5, July-October 1999. 7. Habraaken, J., Supports: An Alternative to Mass Housing, 1972 8. Kendall, Stephen, Open Building; Advanced Buildings Newsletter, Vol. 1 no. 18, pg. 12, Summer 1997. 9. The Environmental Research Group, School of Architecture, UBC, Life-Cycle Energy Use in Office Buildings, Athena Sustainable Materials Institute, Ottawa, August 1994 10. M. Gordon Engineering; Demolition Energy Analysis of Office Building Structural Systems, Athena Sustainable Materials Institute, Ottawa, March 1997 11. Tomonari Yashiro, Musashi Institute of Technology, What Kind of Built Stock are we Making for the Future? The Problem of Short Life Buildings in Japan, CIB Workshop: Construction Beyond 2000, Espoo, Finland, June 1992,
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