February 2011 – When it comes to significant upgrades, or ‘adaptations’, of existing offices, not all buildings are created equal. In fact, ground-breaking research by SARA J WILKINSON indicates that the likelihood of an upgrade depends on characteristics such as building height, floor area… even aesthetic values.
The built environment contributes around half of all greenhouse gas (GHG) emissions and Australian offices account for 12 percent of emissions. As authorities seek to lower the effect cities have on climate change, adaptation offers a realistic means of lowering emissions. The 1200 Building Program developed by the City of Melbourne aspires to sustainably adapt central business district (CBD) offices to become a carbon-neutral city by 2020. Through examination of previous adaptations it is possible to identify the nature and extent of typical adaptation, and determine the potential for sustainability; this article reveals some key trends in office adaptation and suggests some directions in terms of sustainability. The analysis focused on extensive adaptations classed as ‘alterations and extensions’ and examined every adaptation between 1998 and 2008.
DRIVERS FOR ADAPTATION
Sara J Wilkinson
Adaptation is ‘any work to a building over and above maintenance to change its capacity, function or performance’; in other words, ‘any intervention to adjust, reuse or upgrade a building to suit new conditions or requirements’ (Douglas 2006). The factors driving adaptation are grouped under economic, social, environmental, technological, legal and physical categories. For example, the local economy contributes to adaptation, along with other attributes such as age, physical condition, heritage value, size (i.e. smaller buildings were more marketable), and user demand. Building quality and character were found to be determinants of successful adaptation, as was accessibility to and within buildings, along with layout and flexibility for a range of differing uses.
As offices age they are prone to obsolescence. Physical attributes such as size and height, depth, structure, envelope and cladding type, internal space layout and access, services, acoustic separation and fire safety all affect adaptation. Other attributes are site-related (car parking, orientation, external noise and external access), size-specific (floor area, height, depth, floor shape, grids and floor to ceiling height), structure-specific (penetration for services), envelope-focused (cladding and thermal issues), services-related (to meet new use requirements), focused on acoustic separation (floors and partitions, flanking transmission) and fire protection (means of escape, brigade access, detection and alarms, prevention of spread of flames). Location is important and older buildings often occupy prime sites. Within the paradigm of sustainability, location can be interpreted as accessibility to the building’s user group; transport nodes such as rail and bus transport systems add to the desirability of a property for adaptation.
SUSTAINABILITY ISSUES
The typical measures to address shortcomings in the sustainability of existing buildings are energy efficiency and water conservation measures, including building management systems, adoption of low-energy T5 lighting, use of rainwater harvesting, water reuse and recycling, as well as low-consumption appliances. The Green Star assessment tool typically evaluates sustainability in terms of building management, indoor environment quality, energy, transport, water, materials, land use, site selection and ecology, and, finally, emissions. Adaptation provides the opportunity to retrofit sustainability and to reduce the overall environmental footprint of the building.
RESEARCH APPROACH
A database of commercial buildings was assembled using numerous sources including Cityscope, PRISM and commercial data produced by the Property Council of Australia (RPData 2008, DSE 2008, PCA 2007, PCA 2008). Adaptation events were extracted from building permits issued by the Building Commission in Victoria. Empirical data was gathered by visual surveys. The geographic area for the study was the original CBD grid laid out by Hoddle, continuously occupied since the 1830s and a well-developed, mature commercial market.
Principal component analysis (PCA) was used to uncover, disentangle and summarise patterns of correlation within a data set. PCA condenses information contained in a number of original variables into a smaller set of new composite factors. It was used to reduce the dimensionality of office building attributes and adaptation data. Assigning meaning to a PCA solution involves interpretation of factor loadings. Some 5290 adaptation events were analysed with 54 attributes progressively reduced to 12 attributes identified as most influential in adaptation.
MOST INFLUENTIAL FACTORS IN ADAPTATION
Three factors containing 12 attributes explain 73.98 percent of the variance in adaptation. These adaptations involved the most extensive works, short of demolition and rebuilding, such as alterations and extensions. Building owners were most likely to engage in this type of adaptation from 1998 to 2008, indicating high levels of confidence in the market. Extensive adaptations were perceived to recoup investment through higher rental yields, increased capital values and lower vacancy rates. The frequency and level of activity suggest good potential for integrating sustainability. Each group of building attributes was allocated a name (see table below).
FACTOR ONE: PHYSICAL – SIZE
The variables – number of storeys, gross floor area (GFA), Property Council of Australia building quality grade, site boundaries, typical floor area and site access – explain 44.86 percent of the variance in adaptations. Of the six variables, three relate to physical dimensions of the property in terms of floor area and height. Two variables relate to site boundaries (the degree of attachment to other buildings) and site access (number of access/entry/exit points to the building). The final attribute – Property Council of Australia grade – relates to building quality, which is synonymous with size; premium buildings are not small. These attributes are ‘physical – size’ attributes. Given that physical attributes were found to be most influential in adaptation, there is excellent potential to modify these components to reduce their environmental impact.
FACTOR TWO: LAND
Three attributes – street frontage, vertical services location and location –explain 19.78 percent of the variance. The street frontage (width of the land parcel) and location relate to land. The location of vertical services is a design attribute that influences the flexibility of the space plan to adapt to different configurations of the floor plate. These attributes are influenced by land factors. There is less scope here to introduce sustainability measures per se to these attributes; however, the property location can contribute significantly to transport-related emissions, and emphasis needs to be placed on the provision of facilities for cyclists and the promotion of the use of public transit systems.
FACTOR THREE: SOCIAL
Historic listing, age and aesthetics explain 9.33 percent of variance. Age is negatively loaded, which means that as buildings age they are more likely to be adapted. Aesthetics relates to appearance and indicates that buildings with a poor appearance are less likely to be adapted, and this was borne out in the statistical analysis. These attributes are labelled ‘social’ factors. Again, there is limited direct scope to introduce sustainability measures with these attributes per se; however, there is clearly a relationship between age and embodied energy – as building age increases, the embodied energy content diminishes.
THE LESSONS LEARNED
Significantly, the PCA correlated attributes that previous studies identified as separate, which begs the question: is the relationship between building adaptation and building attributes more complex than previously considered?
Most CBD adaptations were extensive. Physical building and size attributes are the most influential attributes. Where height is concerned buildings were classified as low-rise (up to six floors), medium-rise (seven to 20 floors), high-rise (21 to 45 floors) and sky-rise (46 floors plus). A total of 43.7 percent of adaptations occurred to medium-rise and 30.9 percent to high-rise buildings, with low-rise accounting for the least work (9.4 percent). When GFA was analysed, 57.7 percent of work occurred to buildings of less than 50,000 square metres.
Appearance is important in major adaptations, with the most aesthetically pleasing buildings accounting for 29.5 percent of works, and the least aesthetically pleasing ranked last, with 2.2 percent of adaptations (see Chart 1 below).
Building quality is significant. PCA Premium, Grade A and B stock have higher rates of adaptation than Grade C and D stock. With the degree of attachment to other buildings (site boundaries), in the CBD smaller low-rise buildings tend to be attached on two sides, with the larger high-rise stock more likely to be detached. Detached buildings are easier to adapt externally as owners can get access to elevations; these buildings represented 53 percent of adaptations, whereas buildings attached on three sides underwent 8.3 percent of adaptations.
To a lesser extent, building width is critical and grouped with the location of vertical services and location. Some 71.17 percent of adaptations occurred to buildings 50 metres wide or less. Location featured in factor two, and buildings in prime, low-prime and low-secondary underwent 78 percent of adaptations whilst those in fringe and high-secondary locations were least likely to be adapted (see Chart 2 below).
No research has investigated so many adaptations in a geographical area – in effect a census of all events – over such a long period (1998 to 2008). Just 12 attributes explain 73.98 percent of variance in adaptation. The most influential building attributes were: physical/size, followed by land characteristics and lastly by the social attributes. Characteristics perceived to be influential, such as environmental attributes, had limited influence on adaptation from 1998 to 2008. This will change over time as environmental features become more common in the stock and are embedded more broadly in the BCA. If the study were replicated for current adaptations, it is likely environmental attributes would have increased influence.
CONCLUSION
Given that there is much adaptation and an increasing amount of adaptation, there is great potential for sustainable retrofit. Through enhanced understanding of the patterns of commercial building adaptation, it is possible to strategically plan and target policy-making to optimise efforts to deliver the 38 percent reductions in building-related greenhouse gas emissions and the objectives of the 1200 Buildings Program.
References
Douglas, J (2006). Building Adaptation. Butterworth Heinemann.
DSE (2008). PRISM, State Government of Victoria.
PCA (2007). Benchmarks Survey of Operating Costs. Melbourne Office Buildings. P. C. o. Australia: 36.
PCA, A. (2008). existing buildings // survival strategies. A toolbox for re-energising tired assets. PCA: 67.
RPData (2008), Melbourne Cityscope, Cityscope Publications Pty Ltd.
Sara Wilkinson is a chartered building surveyor and a Fellow of the Royal Institution of Chartered Surveyors (RICS). She worked for several years in London providing professional building surveying services to clients, particularly in commercial refurbishment, before starting an academic career. She completed an MPhil in 1995 examining conceptual understanding of green buildings. In 2002, Wilkinson finished an MA in Social Science Research Methods and in 2010 completed her PhD on building adaptation. She has published many papers and her books include Best Value in Construction, A Greener Home and Property Development. Her research interests include sustainability and adaptation. She is an active member of the RICS Oceania Sustainability Working Group and the Victoria and Tasmania Committee. She is currently based at Deakin University, Victoria.
More information
Sara J Wilkinson s.wilkinson@deakin.edu.au