DELITOS CONTRA LA SALUD PÚBLICA CAPÍTULO ÚNICO

One of the difficulties for any study that examines building energy retrofitting is that every building is unique, with unique characteristics that influence energy consumption and the success of a potential retrofit strategy. The modelling effort required to produce a detailed model of an individual building precludes the generation of sufficient detailed energy models to support general statements about effective retrofit techniques for a larger stock. A simplification is therefore necessary. A commonly used technique is the use of ‘reference’ or ‘archetypal’ buildings (Chidiac et al., 2011a; Douglas, 2006; Guan, 2009a, 2011, 2012; Lam et al., 1997; Lyons, 2008; Rongère & Gautier, 1993; Sehar et al., 2012). The purpose of a reference building is to represent an average or typical building in the segment of the building stock under consideration. The underlying assumption of this approach is that whilst a representative building may not accurately represent any particular building, it will respond to an intervention in a similar manner as a building of a similar form and use, facilitating an understanding of how real buildings are likely to be affected by interventions.

Best practice studies that have developed reference buildings have used statistical data to analyse the building stock under consideration, and identify a number of reference buildings to characterise that stock to a sufficient degree, and with an acceptable level of uncertainty (Deru et al., 2011; Famuyibo et al., 2012; Kavgic et al., 2010). Once these basic forms have been selected, detailed energy models of the buildings, including details of building geometry, construction, mechanical services and internal loads, are constructed. Evans et al. (2014), in the UK, have developed a method of attaching database information (including energy consumption) to 3D mapping sources, and then to create a 3D stock model with actual geometry and construction details, which can then be simulated with the use of appropriate reference services and activities.

Reference building models can be used for a variety of purposes. The energy consumption for each building type in each climate zone can be predicted with BPS, and the predicted consumption multiplied by the number of each buildings in that zone, to create a bottom-up stock model of energy consumption. Reference buildings have also been used to examine the impact of new

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technologies on energy consumption (Sehar et al., 2012), improved energy codes and standards (Lyons, 2008), and investigate the response to external stimuli in a manner that is ‘typical’ of a certain building type in a certain location (Guan, 2009a). Importantly, reference buildings can provide consistency in modelling approaches and inputs for simulation users examining different subjects.

Reference buildings do not accurately model the energy use in any particular building since every commercial building is unique, and often the energy use of a building will be heavily influenced by a particular characteristic of that building. A reference building represents a hypothetical building, often with ideal operation and high-performance services that share characteristics with other buildings of that typology. Whilst reference buildings may provide hints that a particular building is performing poorly in some areas, they are not designed to benchmark the performance of a building.

Reference buildings have been developed by numerous bodies internationally to represent the building stock, or a sub-set of the building stock, of a region. Detailed consideration is given below to the US DOE Commercial reference buildings and two reference buildings designed to represent office buildings in Australia.

2.9.1 U.S. Department of Energy Commercial Reference Buildings

Deru et al. (2011) reported on a major study to identify reference buildings to represent common commercial building types in the U.S. Sixteen reference building forms were identified, with three variations to each form to account for difference between new construction, post-1980 construction, and pre-1980 construction. The authors estimated that the template buildings characterised approximately 70% of the commercial building stock in the US, and may be adapted to characterise other commercial building types not directly covered. The project built on previous work (Huang et al., 1991; Huang & Franconi, 1999), and relied on an extensive data resource; i.e. the Commercial Building Energy Consumption Survey (CBECS). CBECS is a nationwide survey of the characteristics and energy use of commercial buildings, undertaken by the US Department of Energy (DOE) every four years, with a sample size between 5,000 and 7,000 buildings.

The building forms identified were: Small Office, Medium Office, Large office, Primary School, Secondary School, Stand-Alone Retail, Strip Mall, Supermarket, Quick Service Restaurant, Outpatient Healthcare, Midrise Apartment, Full Service Restaurant, Small Hotel, Large Hotel,

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Hospital, and Warehouse. The DOE template buildings have been used extensively in a broad range of research projects. The present literature search revealed 144 citations for the original report. Sehar et al. (2012) used the template models to examine the impact of ice storage on office building energy use in different US climates; Ng et al. (2012) simulated the template buildings for an investigation of indoor air quality; and Holmes and Reinhart (2013) use one of the template buildings in their discussion of the impact on climate change on building energy retrofitting.

2.9.2 Australian Buildings Codes Board template buildings

The most commonly used reference building forms for BPS in Australia are the Australian Building Codes Board (ABCB) template buildings. The ABCB developed several representative buildings for use in simulations for benchmarking annual energy consumption when making changes to the energy efficiency measures in the BCA, as well as to evaluate the effectiveness of possible energy saving features for buildings. The forms were designed to ‘reasonably reflect prevailing standards in the diverse stock of buildings’ in Australia (Donnelly, 2002). The basic building forms were developed from a review of Australian Bureau of Statistics (ABS) data for the total cost of buildings approved for construction in Australia in the years 95/96 and 99/00. Five building cost ranges were identified, and these were converted into average areas for each range with the use of typical construction cost/m2 rates. These floor areas were then used as the basis of five basic building form definitions, representing buildings in BCA classes 2-9 (e.g. every building type except single detached dwellings). A definition of the BCA Building Classes is provided as Appendix A. It was assumed that a building form may be common to a number of BCA classes, however the construction, services and usage schedules must be selected according to the building use. No recommendations were provided by Donnelly for construction or internal loads for the representative buildings.

Form A and Form B are relevant to this study, as they represent BCA Class 5 (office) buildings. Form A is designed to approximate typical fabric and internal loads in large commercial buildings, and is stated to be representative of BCA Class 2, 3 or 5 buildings with a gross floor area greater than 2,000 m2. Form B is designed to be representative of Class 5 buildings with a gross floor area less than 2,000 m2, typical of offices on the fringe of CBDs. The basic details of the Form A and Form B building templates are given in Table 2-1.

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Table 2-1 Form A and Form B template building forms developed by ABCB (Donnelly, 2002).

These basic forms have been utilised in numerous buildings simulation studies (ABCB, 2004, 2006a, 2006b; ACADS-BSG, 2002; BRANZ, 2007; Donnelly, 2004; Guan, 2009a, 2009c, 2011, 2012; Lee & Ferrari, 2008; Lyons, 2008, 2009; pitt&sherry, 2010, 2012c; Samarakoon & Soebarto, 2011) for a range of purposes, however they have been used primarily in ABCB studies used to inform BCA energy efficiency provisions. The present literature review identified 12 Australian studies that utilised Form A, and eight that used Form B, with five having used both. The ABCB, or consultants to the ABCB, have used these templates in multiple studies looking at the impact on building energy consumption of changes to the energy efficiency provisions within the BCA (ABCB, 2004, 2006a, 2006b; Bannister, 2004; Lyons, 2008, 2009). Guan (2011, 2012) and BRANZ (2007) utilised the Form A building to simulate the impact of climate change on building energy use. Samarakoon and Soebarto (2011) used the template form to test the sensitivity of building energy use to occupancy inputs. There is some inconsistency in the construction, services and occupancy input values used to simulate office buildings in these studies. A detailed review of the range of modelling assumption for key occupancy and services variables is given in Chapter 6.

Reference ID A B

Typical locations CBD of capital city or major

regional town

CBD edge, major regional towns or resort centres

BCA Classes and building usage

2 = apartments 3 = hotel 5 = office tower

2 = apartments 3 = hotel 5 = office block 9 = health care building

Gross Floor Area 10,000 2,000

Net Lettable Area

(NLA) (m2) 9,000 1,800

Storeys 10 3

Aspect ratio 1:1 2:1

Length (m) 31.6 36.5

Depth (m) 31.6 18.3

Perimeter Zone depth

(m) 3.6 3.6

Floor-floor height (m) 3.6 3.6

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2.9.3 Zero Carbon Australia Buildings Plan

The Zero Carbon Australia Buildings Plan (ZCA, 2013) set out to demonstrate how existing buildings in Australia could be effectively decarbonised, becoming net-zero energy within ten years. The researchers created template buildings for energy modelling on the basis of a multi-stage process reliant on expert input. The first step in typology development used the City of Melbourne 1200 Buildings Segmentation Study (Arup, 2009) and municipal rates collection data to develop draft typologies. Numerous workshops and individual meetings were held with experts from academia and industry to identify groupings of building characteristics. From this several typologies distinguished by building function (e.g. education), age (e.g. 1950 – 1980), and location (by climate zone) were developed. Typologies included basic detail on building size, location, geometry, fabric, services, and hours of operation. These draft typologies were presented to a larger workshop with participants from industry, government, and academia, and scrutinised for accuracy and usefulness. Following the workshop a range of sources, most significantly the National Exposure Information System (Geoscience Australia, 2006) database, were studied to identify any building typologies that were poorly represented in the building stock, and therefore unnecessary, and any areas that had been missed. Unnecessary building types were removed, and the typologies were finalised. Twenty- two typologies were developed, including four reference office buildings, namely pre-1945 Masonry Load Bearing, 1945-1980 Curtain Wall, 1980-2000 Curtain Wall and 2000-onwards Post BCA Energy Efficiency Provisions. The four office typologies were particularly relevant to the present study, as they are held to be representative of a significant portion of the Australian commercial office stock. Further detail of the three buildings modelled is given in Table 2-2. (The post-2000 building was not modelled, as it was assumed that upgrades were management improvements and system tuning).

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Table 2-2 Building typologies and energy modelling inputs developed by ZCA (2013) to represent commercial office buildings in Australia.