embodied carbon and the decision to demolish or adapt

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EMBODIED CARBON AND THE DECISION TO DEMOLISH OR ADAPT Hannah Baker1 & Alice Moncaster2 1

Future Infrastructure and Built Environment Centre for Doctoral Training, Department of Engineering, University of Cambridge, UK, [email protected] 2 Senior Lecturer, School of Engineering and Innovation, Open University, UK, [email protected]

Abstract: Embodied and operational carbon are both an important part of the built environment’s impact on climate change. Two mitigation strategies identified for reducing embodied and lifecycle emissions include refurbishing existing buildings or demolishing existing buildings and replacing them with more efficient new buildings. This paper explores existing literature assessing the decision between demolition and adaptation, then through a quantitative analysis assesses three factors regarding lifecycle assessments which were identified through a critique of existing research. The analysis concludes: embodied emissions associated with the existing structure should not be included in decision-making, as they have already been ‘spent’; the decarbonisation of the grid is important to consider when comparing strategies, as the cumulative emissions from a less efficient refurbishment are likely to take longer to exceed emissions associated with new build; absolute values for emissions (the total amount for the whole building) should be considered when comparing adaptation to new build projects , since many existing papers focus on emissions per square metre and like-for-like replacements which are deemed to be unrealistic. The quantitative analysis is supported by a qualitative analysis of two focus group with industry and academic experts in the built environment. These focus group discussions showed that there are still methodological issues with life cycle assessments, such as uncertainties with lifespans and data reliability. Participants felt these need to be addressed before legislation and financial incentives can be introduced. A commonly mentioned suggestion to improve the current methodology included collecting more data through case study investigations. Both the qualitative and quantitative analyses build upon the existing research identifying key concepts which need to be addressed and improved upon if considering embodied emissions in the decision to demolish or adapt existing buildings.

Keywords: Embodied Carbon, Demolition, Adaptation, Decision-making, Life-cycle Assessments

1

ZEMCH 2018 International Conference, Melbourne, Australia 29th January – 1st February 2018

1

Introduction

Embodied and operational carbon are both an important part of the built environment’s impact on climate change (Brown et al., 2014; Cuéllar-Franca and Azapagic, 2012; Hacker et al., 2008; Monahan and Powell, 2011). Both Oregi et al. (2017) and Weiler et al. (2017) report that the building sector contributes approximately 30% of the annual global greenhouse gas emissions, referencing the report from the Commission of the European Communities (2014). To try and reduce this contribution, Ibn-Mohammed et al. (2013) describe the introduction of a mandatory carbon reporting scheme for companies in the UK. The UK Government has indicated that embodied emissions are likely to become key metrics to be addressed when considering the whole-life sustainability of a building, and Ibn-Mohammed et al. (2013:240) concludes “its inclusion in the decision-making process is therefore of the utmost importance”. Pomponi and Moncaster’s (2016a) systematic review of the academic literature indicates that there are several mitigation strategies to reduce embodied emissions in the built environment. One of these includes retrofitting the existing housing stock to improve energy efficiency, while another includes the opposite, demolishing existing buildings and replacing them with new, with the authors (Boardman, 2007; Dubois and Allacker, 2015) stating that the life-cycle emissions are lower for particular scenarios. This paper explores these two mitigation strategies by comparing when the environmental impact is higher or lower for the demolition or adaptation of existing buildings. A literature review summarises and provides a critique of existing research. This is followed by a quantitative analysis to show how a building’s lifetime emissions can vary when considering different factors such as: whether or not to include existing emissions in the analysis; decarbonisation of the energy grid; and increasing floor areas. These factors were identified through critiques of existing research. A qualitative analysis of two focus group discussions is then used to investigate current attitudes towards embodied carbon’s inclusion in decision-making and to suggest potential improvements. 2

Literature Review

2.1 2.1.1

Embodied carbon and life-cycle assessments Life cycle stages

Embodied emissions are associated with every stage of a building’s lifecycle. The Commission of the European Communities’ (2014) TC350 framework defines the life cycle stages shown in Table 1. Ideally, all stages should be considered through a ‘Cradle-tograve’ or even a ‘Cradle-to-cradle’ concept to ensure correct decisions are made (Pomponi and Moncaster, 2016a). For example, if the focus is only on stages A1-A3, a strategy may be chosen which has fewer emissions for this product stage but more over the building’s lifetime. If conducting a life cycle assessment (LCA), operational emissions should be considered alongside embodied emissions. Existing research has tended to focus on operational energy because this is where policies have previously focused. Szalay (2007) discusses the European Commission’s Energy Performance Directive which only encompasses operational emissions and recommends embodied energy is taken into account during

2 BAKER & MONCASTER_PAPER 39


assessments. Although authors such as Cuellar-Franca and Azapegic (2012) found that 90% of carbon emissions were associated with the use-stage and only 9% with embodied carbon, others argue that as embodied emissions are calculated for each life-cycle stage and operational energy decreases, embodied energy will contribute a higher proportion of overall emissions (Ibn-Mohammed et al., 2013). Table 1: Life cycle stages of a building. Data source: BS EN 15978:2011 (BSI, 2012)

2.1.2

Uncertainties and sensitivities

A current issue with LCAs is the sensitivity and uncertainty of the methodology (Dixit et al., 2013). A recent study by Oregi et al. (2017) assesses emissions for 775 refurbishment scenarios. Their sensitivity analysis included alterations to: the service life of the building and its components; transportation distances; climatic zones; embodied energy calculated for products; uncertainty regarding occupancy and conversion factors from energy to carbon. Their results are shown in Figure 1 and demonstrate the range of values which emerged for each life-cycle stage. Pomponi and Moncaster (2016b) conducted a project aiming to ‘bridge the gap’ between whole life carbon theory and its practical implementation. Three specialist carbon consultants assessed five case studies, four new build and one residential refurbishment. The consultants used the BS EN15978 standard (BSI, 2012) as a framework and the same data as a starting point, including a bill of quantities and technical drawings. The final report and subsequent paper (Pomponi et al., In Press) discusses methodological issues identified through a comparison of the three consultants’ LCAs as the results showed significant variations. These were caused by various assumptions including: the study period; type of floor area (gross external, gross internal or net internal); and material/spatial boundaries (Pomponi and Moncaster, 2016b). Although the report’s intention was not to compare adaptation to demolition and new build, if the results are normalised to emissions per m2 (Figure 2), the consultants’ results have different



conclusions for which strategy has the lowest emissions, reiterating concerns that there needs to be methodological improvements.

Figure 1: Percentage of global impact for each life-cycle stage (see Table 1) for refurbishment scenarios and their sensitivity analysis. Source: Oregi et al. (2017: 22)

Whole Life Carbon 60 years (kgCO2/m2)

Refurbishment

New build office

New build residential

3000 2500 End of Life (C1 - C4)

2000

Maintenance (B2) and Repair, Refurbish, Replace (B3 - B5)

1500

Consturction (A5)

1000

Transport (A4)

500

Production (A1 - A3)

Consultant 3

Consultant 2

Consultant 1

Consultant 3

Consultant 2

Consultant 1

Consultant 3

Consultant 2

Consultant 1

0

Figure 2: Consultant responses for whole life carbon assessment of three case studies using 60year lifespan (excludes B6 lifecycle stage). Reproduced and adapted from Pomponi and Moncaster (2016b).

2.2 Demolition versus adaptation (refurbishment) Demolition refers the end of a building’s lifespan caused by man-made destruction (Thomsen and Flier, 2009), whereas adaptation typically refers to retaining part or all of an existing structure (Wilkinson et al., 2014). Adaptation can vary from a change in the



internal space; the performance (e.g. energy efficiency), function, size or even location (Schmidt III et al., 2010). Within the literature there are various terms used including retrofit, refurbishment and renovation; which are often interchangeable with adaptation. This section reviews literature focusing on embodied emissions and/or LCAs alongside the decision to demolish or adapt. It is structured in three parts which reflect factors affecting this decision. These factors/sub-headings were identified through a critique of existing research papers’ methodologies and results. 2.2.1 The inclusion or exclusion of existing emissions (‘sunk costs’) Existing buildings will have emissions associated with their past construction, however their inclusion in the decision-making process is debatable as they are emissions which have already been ‘spent’. In some academic papers they are considered, whereas in others they are dismissed. Gaspar and Santos (2015) evaluate a family dwelling in Portugal for its embodied carbon. Their analysis includes a quantification of the material in the existing structure as well as the new material required for a new build replacement or the refurbishment of the existing building where 64% of the initial structure is demolished. They found that refurbishment has lower embodied emissions than the new build. However, if these historical costs are included, there can be additional complications with calculations. This was found during a study by Bin and Parker (2012) who tried to quantify the embodied emissions of an early 20th Century house in Canada. In other studies, such as Erlandsson and Levin (2005), the historical emissions, are not seen as relevant today and are referred to as ‘sunk costs’. Weiler et al. (2017) assessed four scenarios for a multifamily house in Germany using a 50 year lifespan. These included: an existing 1975 house with no refurbishment; the existing 1975 house with medium refurbishment (corresponding to a standard between kfW70 – kfW1001); an advanced refurbishment to passive house2 standards; and a newly constructed 2016 building with kfW70 standard. They used two approaches to calculate the embodied emissions for the refurbishment strategies. In the first, they include the emissions associated with the existing building and the additional emissions required for refurbishment, stating that this allows the refurbished building’s environmental impact to be compared to a newly constructed building. Their second approach only considers the energy used for refurbishment, which they say allows the refurbishment to be compared to demolition and new build, which is the focus of this paper. Weiler et al’s results showed that an advanced refurbishment (excluding sunk costs) had the fewest emissions (1.42 million kgCO2e); followed by new build to 2016 standards (1.66million kgCO2e); then a medium refurbishment excluding sunk costs (1.70 million kgCO2e); followed by doing nothing (3.14 million kgCO2e). Overall, the majority of papers reviewed for this paper did not include calculations for the existing building’s emissions which can be used as an indication they are not commonly considered (Hacker et al., 2008; Olsson et al., 2016; Wastiels et al., 2016). The impact of their inclusion is explored further in Section 4.1. 1

KfW-70 = maximum annual primary energy requirement 70 kWh/m 2 & KfW-100 = maximum annual primary energy requirement 100 kWh/m2 (energiesparen im haus halt, 2017) 2 “A Passivhaus is a building, for which thermal comfort can be achieved solely by post-heating or postcooling of the fresh air mass, which is required to achieve sufficient indoor air quality conditions – without the need for additional recirculation of air” (Building Research Establishment Ltd., 2011) 5 BAKER & MONCASTER_PAPER 39


2.2.2

Variations in operational energy standards

Depending on the level of retrofit, the operational energy standards will vary and can lead to different decisions regarding a renovation’s environmental impact compared to new build. For example, Dubois and Allacker (2015) highlighted that previous papers (Morelli et al., 2014; Power, 2008) found refurbishment to have a lower environmental impact than new build but only focused on ‘deep retrofit’ strategies, which they define as a 60% or more reduction in operational energy. Using a series of equations they argue that focus should be either on replacing existing buildings with higher performing new build or using deep retrofit strategies. They feel that there should not be small scale subsidies for renovation as this locks in energy and prevents improvement in the future. However, this conclusion does not consider the decarbonisation of the fuel supply. Although operational energy will remain the same, the carbon associated with this is likely to reduce (Alderson et al., 2012; Kannan and Strachan, 2009). In addition, operational energy is not just a technical matter and is influenced by the users and economic valuations. Various authors including Greening et al. (2000); Brännlund et al. (2007) and Chitnis et al. (2013) explore the ‘rebound effect’ which can offset potential energy savings. Despite this critique, Dubois and Allacker’s paper does highlight the importance of considering the level of intervention and refurbishment, as also seen in Weiler et al’s (2017) paper discussed in Section 2.2.1. Rather than comparing adaptation against new build, other papers focus solely on the lifecycle impacts of different refurbishment strategies. For example, Brown et al (2014) evaluated refurbishment measures identified in a survey of 1,400 single and multi-family dwellings. Results showed the measures which contributed the highest proportion of emissions were replacing the windows and mechanical ventilation strategies. In a study by Schwartz (2016), two social housing blocks on the same estate in Sheffield, UK, were evaluated to compare the actual refurbishment measures to the optimal refurbishment measures. The optimal result showed that the operational emissions of Building A could have been reduced to 795kgCO2/m2 compared to the original refurbishment which was at 923kgCO2/m2, showing that decision-making at the initial design stage regarding environmental impact could have been improved. The study showed that emissions were significantly reduced by insulating thermal bridges and increased by using brick cladding. A comparison between the two buildings indicated that one used less CO2 over the lifetime and this is assumed to be because of the different spatial arrangements, orientations and solar gains. These factors would be easier to control with new buildings. A limitation linked to the possible level of intervention for refurbishments is heritage, a key factor considered in the decision to demolish or adapt existing buildings (Baker et al., 2017). In some refurbishment scenarios, such as those outlined by Wastiels et al. (2016) external wall insulation was not allowed because of urban development rules and in Oregi et al’s (2017) analysis they assume there was no historic or urban restrictions. In reality, as acknowledged by Olsson et al (2016:30) “cultural heritage values make some building envelope measures impossible”. Work by organisations such as Historic England, formally known as English Heritage are conducting research to try and overcome these constraints (Historic England, 2017). The variation in the operational energy standards is also important to consider in the new build scenarios. Alba-Rodríguez et al. (2017) evaluated the environmental footprint (EF) for the refurbishment of a multi-family housing block compared to demolition and new build using global equivalent hectares (gha) as the units over a 25 year lifespan. Although, the



housing was in very poor condition, the EF was 0.093gha/m2 for refurbishment compared to 0.214 gha/m2 for the new build. If that new build reached newer standards for operational energy at the time the paper was submitted for publication in 2016, rather than when the decision was made in 2006, the environmental impact would have been 0.200 gha/m2. Operational energy standards will have a significant influence on the LCAs of buildings. This section has shown that it vital to consider the effect of different levels of intervention for refurbishment and standards for new build, as well as considering what will affect operational emissions in the future, such as the decarbonisation of the grid and the uncertainty of user behaviour. 2.2.3

Floor areas

Existing literature regarding demolition and adaptation tends to focus on like-for-like replacements (Alba-Rodríguez et al., 2017; Gaspar and Santos, 2015; Weiler et al., 2017), which seems to be unrealistic. Baker and Moncaster’s (2017) case study of a masterplan regeneration site in Cambridge, showed it is often desirable for developers to demolish existing buildings to build back bigger because of economic viability. Morelli et al. (2014) evaluate the decision of demolition versus adaptation economically. Their evaluation favoured the renovation of a multi-family 1850-1930 house in Denmark over new build. However, values given are per m2, it is likely that the square meterage will be increased for new buildings. If this is the case, there will then be higher returns on the building due to the higher floor areas. Changing floor areas were acknowledged by Wastiels et al. (2016) who evaluated different options for a single family house in Belgium. Although the house remained at three stories, in the new build option the basement and attic became useable creating a 78% increase in useable floor space from the renovation strategy. Their results showed that the environmental impact of the new building was approximately 20% higher than the box-inbox renovation. At the end of their paper, they discuss how the new build performs better per square meter of heated floor space. Although this is true, this type of analysis needs to be treated with caution. If the existing building is replaced by a larger building and not a like-for-like construction the absolute figure for environmental impact will be higher and unrepresentative if viewed on a CO2e/m2 basis. 3 Methodology This paper reports on part of a 3-year PhD project assessing the decision to demolish or adapt existing buildings on masterplan sites, where the consideration of embodied energy has been identified as an important aspect to consider (Baker et al., 2017). A quantitative analysis is used to demonstrate how the inclusion of different factors can influence LCAs and a qualitative analysis reflects current viewpoints towards the consideration of embodied energy in decision-making. 3.1

Quantitative analysis

The quantitative analysis uses secondary data to assess how the inclusion of ‘sunk costs’; decarbonisation of the grid; and changing floor areas, affect the outcome of LCAs. Data was selected by evaluating whether appropriate figures required to assess the factor were 7 BAKER & MONCASTER_PAPER 39


included in the paper/report. Primary data was not used because the purpose of this paper is to demonstrate different concepts and how LCA figures can change depending on the inclusion or exclusion of these factors, thus wasn’t deemed necessary. 3.1.1 Potential impact of ‘sunk costs’ (emissions associated with existing materials) Using data from two papers: Weiler et al. (2017) and Gaspar and Santos (2015), the effect of including ‘sunk costs’ was evaluated by calculating the percentage change in the embodied emissions with and without its inclusion. Weiler et al. (2017) provide scenarios including and excluding emissions calculated for the existing structure. These values have been used to calculate the ‘sunk costs’ (see Equations 1-3). Gaspar and Santos (2015) provide data for three scenarios, these are outlined in Table 2. The values determined as ‘sunk costs’ for the purposes of this paper are identified.

Table 2: Scenarios and values identified as ‘sunk costs’ using Gasper and Santos (2015) data

3.1.2

Operational energy levels and decarbonisation

Using values from Weiler et al’s (2017) paper, the effect of decarbonisation is analysed. Weiler et al. (2017) provided final figures for:  Primary energy during the whole lifecycle (50 years) in kWh  Greenhouse gases emitted during the whole lifecycle (50 years) in kgCO2e



An approximate emission factor was calculated using Equation 4 producing a value of 0.279 kgCO2e/kWh (see Table 3). In the UK, the Government aims to reduce carbon emissions by 34% by 2020 and 80% by 2050 compared to 1990 levels (HM Government, 2008). Table 4, displays the adjusted emission factors and annual emissions if these values are used to decarbonise the grid and applied to the initial emission factor. It is important to note that these emission factors and decarbonisation figures are unlikely to be accurate, however they are being used to demonstrate a concept and the potential effect of decarbonising the grid. Annual operational energy and emissions have been calculated using Equations 5 and 6. The method used to calculate cumulative emissions on a yearly basis is shown in Figure 3, this was applied to Weiler et al’s scenarios (excluding existing emissions).

Table 3: Calculations for emission factor and annual operational energy using data from Weiler et al (2017) study. See equations 4 and 5 Figures provided by Weiler et al (2017) Greenhouse gases Primary use stage emitted during 50 energy during 50 year years (use stage life-cycle - kWh only) - kgCO2e Original construction Medium refurbishment Advanced refurbishment New build

2,950,200 1,554,000

10,570,900

0.279 (3sf)

211,418

5,568,250

0.279 (3sf)

111,365

0.279 (3sf)

90,250

0.279 (3sf)

101,073

4,512,500

1,259,350 1,410,400

Calculated figures for this paper Emission factor Annual operational calculated (see energy (see equation 4) equation 5) - kWh kgCO2e/kWh

5,053,650

Table 4: Approximate emission factors and average operational annual emissions taking into account decarbonisation (see equation 6). Original data used: Weiler et al (2017)

Emission factor used* kgCO2e/kWh (3sf)

Average annual operational emissions calculated for this analysis (see equation 6) kgCO2e*

Original construction Medium refurbishment Advanced refurbishment New build

2050

0.279

0.184 (34% reduction)

0.056 (80% reduction)

59,004

38,943

11,801

31,080

20,513

6,216

25,187

16,623

5,037

28,208

18,617

5,642

*Use with caution. Rough results obtained for the purposes of demonstrating a concept



1

A Year

B Medium refurbishment cumulative emissions – including decarbonisation

2

2016

103921

C Medium refurbishment cumulative emissions – not including decarbonisation 103921

3

2017

=B2+31080

=B2+31080

4 5 6 7 …. 35 36 37

2018 2019 2020 2021 … 2049 2050 2051

=B3+31080 =B4+31080 =B5+20513 =B6+20513 … =B34+20513 =B35+6216 =B36+6216

=B3+31080 =B4+31080 =B5+31080 =B6+31080 … =B34+31080 =B35+31080 =B36+31080

D Description

Production emissions for medium refurbishment Production emissions + annual operational emissions “-” “-” “-” “-” … “-” “-” “-”

Change in annual emissions when decarbonisation considered. Assumption that emission factors reduce in 2020 and 2050 (see Table 3).

Figure 3: Method used to calculate cumulative emissions. Data used: Weiler et al (2017)

3.1.3 Floor areas In Weiler et al's (2017) study the building is a like-for-like replacement. This paper uses values obtained per m2 to assess absolute (total) values for environmental impact and at which point the medium refurbishment, which currently has the highest environmental impact is equal to the new build’s impact as the new build’s floor area increases. The same method is then applied to the values obtained in Pomponi and Moncaster's (2016b) study. The useable heated floor area provided in Weiler et al.’s (2017) paper is 1635m2, this was used to calculate the emissions per m2 for the new build scenario using equation 7, equation 8 shows the actual values used. A calculation was not required for the refurbishments as it is assumed their floor areas remain constant. The method used to calculate the effect of increasing floor area and when the absolute value of new build exceeds the refurbishment strategy is shown in Figure 4.

𝑁𝑒𝑤 𝑏𝑢𝑖𝑙𝑑 𝑒𝑚𝑖𝑠𝑠𝑖𝑜𝑛𝑠 𝑝𝑒𝑟 𝑚2 =

𝑇𝑜𝑡𝑎𝑙 𝑒𝑚𝑖𝑠𝑠𝑖𝑜𝑛𝑠 𝑓𝑜𝑟 𝑛𝑒𝑤 𝑏𝑢𝑖𝑙𝑑 𝑠𝑐𝑒𝑛𝑎𝑟𝑖𝑜 (7) 𝑈𝑠𝑒𝑎𝑏𝑙𝑒 ℎ𝑒𝑎𝑡𝑒𝑑 𝑓𝑙𝑜𝑜𝑟 𝑎𝑟𝑒𝑎

𝑁𝑒𝑤 𝑏𝑢𝑖𝑙𝑑 𝑒𝑚𝑖𝑠𝑠𝑖𝑜𝑛𝑠 𝑝𝑒𝑟 𝑚2 =

1,657,793 𝑘𝑔𝐶𝑂2 𝑒 = 1013.9 𝑘𝑔𝐶𝑂2 𝑒/𝑚2 (8) 1635 𝑚2



Figure 4: Method used to calculate absolute carbon emissions as floor area increases. Data used: Weiler et al (2017)

3.2 Qualitative analysis Two focus group discussions were analysed to investigate current attitudes towards embodied carbon. These focus groups took place as part of a UK embodied energy symposium in April 2016 with industry and academic experts in the built environment (see De Wolf et al., 2017 for more details). Each focus group lasted 40 minutes and included 8-9 people. The question discussed was: “How can embodied energy be incorporated in the decision to demolish or retain existing buildings?” Initially everyone was asked for their viewpoint ‘one-by-one’ and then the topic opened up for discussion. The focus groups were recorded (permission was obtained by participants) and transcribed. These were analysed to evaluate what key themes emerged using grounded theory methods, where qualitative data is coded (Silverman, 2013). Two iterations of coding have been completed to date. In the analysis these codes are referred to as ‘discussion points’. 4 4.1

Analysis Quantitative analysis

4.1.1 Potential impact of including existing emissions Figure 5 shows two bar charts indicating the embodied emissions for the production lifecycle stages with and without the emissions associated with the existing structure (sunk costs). The overall values increase by 36.7-49.0% in Gaspar’s study and 73.8%-89.0% in Weiler et al’s. Although their inclusion does not affect how the strategies of refurbishment measures and new build rank against one another, there is a percentage change in the difference between them. For example in Gaspar and Santos’s study, if the existing 11 BAKER & MONCASTER_PAPER 39


emissions are included the percentage difference between the two strategies is 28.3%. If the ‘sunk costs’ are excluded the percentage difference is 17.8%. This is unsurprising as the new build strategy considers 100% of the existing structure and the refurbishment strategy only includes 64%. As shown by Figure 6, when the whole life cycle is taken into account the proportion of emissions is significantly reduced to 5.4 – 9.3% in Weiler et al’s study, but still affects final figures for LCAs.

2000 1800 1600 1400 1200 1000 800 600 400 200 0

400000

Embodied emissions (kg Co2e)

Embodied Energy (GJ)

This paper agrees with Erlandsson and Levin's (2005) viewpoint that these are historical emissions and should be dismissed and with Weiler et al. (2017) who state that the emissions associated with the existing building should not be included when comparing a refurbishment strategy to demolition and new build. The existing emissions are difficult to account for and have already been invested. The changes in values that they cause may lead to misleading results. Instead, the energy required to demolish the existing structure should be included in the calculations for replacement buildings as these emissions have not already been invested.

350000 300000 250000 200000 150000 100000 50000 0

Refurbishment

New build

New Embodied Emissions

Medium Advanced refurbishment refurbishment

Sunk costs

New Embodied Emissions

New build

Sunk Costs

Figure 5: Inclusion of existing emissions (sunk costs) in the production lifecycle stage. Data sources: Left: Gaspar and Santos (2015); Right: Weiler et al (2017)

Sunk Cost Medium refurbishment New EE Use

Advanced refurbishment

End of life New build 0

500000

1000000

1500000

2000000

Lifecycle emissions - 50 years - (kgCo2e) Figure 6: Inclusion of existing emissions (sunk costs) in whole lifecycle. Data source: Weiler et al (2017)

4.1.2 Operational energy When decarbonisation of the grid is included in the annual operational emissions for Weiler et al.’s study, the overall lifecycle impact of all three scenarios reduces. In the original 12 BAKER & MONCASTER_PAPER 39


scenarios which excluded decarbonisation (Figure 7), the existing 1975 building with no change had the highest environmental impact; followed by the medium refurbishment; new build and then advanced refurbishment. In the example shown, the cumulative emissions for the medium refurbishment exceed the new build after 37 years, because the value calculated for the operational energy is 10.2% higher than the new. When decarbonisation is included, the cumulative emissions for the medium refurbishment do not exceed the new build (Figure 8) within the 50 year lifespan. Although the new build continues to use less operational energy, the carbon emissions associated with this are lower. A rough calculation shows that in this scenario the medium refurbishment’s emissions will exceed the new build after 90 years, also emphasising the importance that lifespans can have on decision-making. This simple analysis is important as it indicates that less intense refurbishment strategies may have lower life cycle impacts than more energy efficient new build over set lifespans if decarbonisation is included. However, it must be acknowledged that the calculated figures are approximations to demonstrate a concept, in reality they will be subject to uncertainty related to LCA and the decarbonisation of the grid. For example, it cannot be guaranteed how the grid will decarbonise in the future and issues such as the ‘rebound effect’ referred to in this paper’s literature review are not considered.

Figure 7: Cumulative emissions over 50 year lifespan excluding decarbonisation of the grid. Original data source: Weiler et al (2017)



Cumulative greenhousegases emitted over 50 year lifecycle (kg Co2e)

1800000 1600000 1400000 1200000 1000000 800000 600000 400000 200000 0 2010

2020

2030

2040

2050

2060

2070

Year 1975 Existing Building

Medium refurbishment

Advanced refurbishment

New build

Figure 8: Cumulative emissions over 50 year lifespan including decarbonisation of the grid. Original data source: Weiler et al (2017)

4.1.3 Floor areas Figure 9 indicates when absolute (total) emissions for the new build scenario exceed the refurbishment scenario by increasing the floor area of the new build and keeping the floor area of the refurbishment constant. In Pomponi and Moncaster’s (2016b) study the average floor area for the original refurbishment was 398 m2, producing 367,000kgCO2e (average value across the three consultants). At this floor area, the new build refurbishment produces 298,000kgCO2e. In reality, new buildings are built bigger than the existing building which is demolished. The total emissions for the new build equal the emissions of the refurbishment (with 398 m2 floor area) when the new build’s floor area increases to 490m2, a 23% increase. In Weiler et al.’s study, the existing building’s useable floor area was 1635m2, with absolute emissions of 1.70million kgCO2e for the medium refurbishment and 1.66million kgCO2e (3sf) for the new build. If the new build’s floor area increases to 1766 m2, an 8% increase, absolute/total emissions begin to exceed the emissions for the medium refurbishment (1.66million kgCO2e) where the floor area has remained constant. These simple calculations have emphasised the importance of not just considered likefor-like replacements and values per m2. If looking at the environmental impact of a new build against refurbishment, it is likely the floor area will increase, thus the absolute (total) emissions should be considered.



Figure 9: Increasing floor area and the associated emissions for refurbishment and new build. Data source: Left: Pomponi and Moncaster (2016b); Right: Weiler et al (2017)

4.2 Qualitative analysis The focus group discussions covered a range of discussion points related to embodied emissions including: current practice; problems; general statements; suggested changes and potential issues with the suggested changes. Overall 48 separate codes were defined. Fifteen of the topics were only raised once and other topics more frequently, topics raised five or more times are shown in Figure 10. The participants felt that the decision to demolish or adapt existing buildings is currently influenced by other factors including: economics; floors areas and heritage values. If embodied emissions are considered, it comes after these factors. One of the reasons given for the lack of consideration was the difficulty in valuing embodied emissions. If evaluating operational energy, it is seen as easier to link with economic savings. In some cases, the participants felt that embodied emissions are reduced as a consequence of other factors, for example reducing material to save on capital costs, consequently reducing embodied emissions.



Figure 10: Points of discussion during focus groups. Only showing those with frequency of 5 or more

The problems identified helped to explain why embodied emissions are not yet universally considered, although the majority of participants felt that they should be. A regularly discussed problem was factoring in uncertainties, such as unknown lifespans and changing occupancies. Participants felt that there is still a lack of data regarding emissions over building lifecycles for new build and refurbishment. As a result, participants felt more data is needed to help reduce uncertainty and improve the transparency and robustness of the methodology, a topic regularly discussed as requiring change. These changes are required to implement other suggested improvements including: government incentives; requiring an LCA assessment as part of planning and/or introducing taxes or other financial drivers. Overall this qualitative analysis has emphasised that the consideration of embodied emissions sits within a complex network of other factors that need to be considered. For it to have more weight in the decision-making process, problems identified such as uncertainties with the methodology and lack of data need to be overcome. One way this could be accomplished is through more cases studies. 5

Conclusions

Embodied and operational energy are important to consider in the built environment because of the emissions associated with them and link to climate change. This paper has reviewed existing literature assessing the life cycle impact of adaptation compared to demolition and new build. The majority of papers reviewed found that over a given lifetime,



usually between 50-60 years, refurbishment strategies had lower environmental impacts than demolition and new build. However, as identified by Dubois and Allacker (2015), these tend to be significant renovations, rather than smaller retrofits. From the literature review three factors were identified as a critique of existing research methodologies. These included: whether or not emissions associated with the existing structure should be included; operational energy levels and whether decarbonisation of the grid should be included; and considering absolute values for emissions rather than per meterage as new build is rarely a like-for-like replacement. These three factors were then assessed through a quantitative analysis and the following conclusions were made: 

 



Emissions associated with the existing structure should not be included in assessments comparing refurbishment to demolition and new build as they are historical. However, it is important the emissions associated with the demolition of these structures is included in the calculations for the new build as these have not already been ‘spent’. Various levels of refurbishment and standards for new build’s operational energy need to be considered. Commonly the operational emissions of new build are lower than medium and less intense refurbishment scenarios. Although, there is a higher investment of embodied emissions for new build, over the lifecycle of buildings, new builds may be favourable to medium refurbishments. However, the UK and other countries are aiming to decarbonise the grid, if this happens, the emissions associated with the operating energy of these buildings will be reduced. This may favour less ‘extreme’ refurbishments as they often begin with a lower investment of embodied emissions. Absolute (total) values for lifecycle emissions should be considered when comparing refurbishment to demolition and new build because it is common for replacement buildings to have larger floor areas. Like-for-like replacements are unrealistic in urban development scenarios.

A qualitative analysis concluded that for embodied carbon to be considered in decisionmaking, there still needs to be improvements in the methodology. This can be achieved by collecting more data and conducting additional case studies. Once improved methodology and data are available, legislation can be introduced equivalent to that for considering and reducing operational carbon. Overall, the literature review and quantitative analysis showed that there are methodological issues when comparing refurbishment to demolition and new build projects, including which factors should be considered. This statement is supported by the focus group discussion where problems related to current methods and the need to improve the robustness were regularly discussed. Both the analyses build upon the existing research identifying key concepts which need to be addressed and improved if considering embodied emissions in the decision to demolish or adapt existing buildings. 6

Limitations and further work

This paper has demonstrated how particular factors affect environment assessments using secondary data and assumptions outlined in the methodology. The aim was to demonstrate whether these concepts should be considered in decision-making, not to provide accurate quantitative figures. Further work will include a new case study investigation comparing the decision between demolition and adaptation whilst taking the recommended factors into account. The qualitative assessment will be extended to include



viewpoints provided during interviews conducted for the PhD project which this paper forms part of looking at the decision of demolition and adaptation holistically. Acknowledgements The authors gratefully acknowledge the EPSRC for funding this research through the EPSRC Centre for Doctoral Training in Future Infrastructure and Built Environment (EPSRC grant reference number EP/L016095/1) and would like to thank all of those that took part in the focus group discussions.

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