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Energy Retrofit

Area: Design, planning and building

Buildings are responsible for approximately 40% of energy consumption and 36% of greenhouse gas emissions in the EU (European Commission, 2021). Energy retrofit is also referred to as building energy retrofit, low carbon retrofit, energy efficiency retrofit and energy renovation; all terms related to the upgrading of existing buildings energy performance to achieve high levels of energy efficiency. Energy retrofit significantly reduces energy use and energy demand (Femenías et al., 2018; Outcault et al., 2022), tackles fuel (energy) poverty, and lowers carbon emissions (Karvonen, 2013). It is widely acknowledged that building energy retrofit should result in a reduction of carbon emissions by at least 60% compared with pre-retrofit emissions, in order to stabilise atmospheric carbon concentration and mitigate climate change (Fawcett, 2014; Outcault et al., 2022). Energy retrofit can also improve comfort, convenience, and aesthetics (Karvonen, 2013).

There are two main approaches to deep energy retrofit, fabric-first and whole-house systems. The fabric-first approach prioritises upgrades to the building envelope through four main technical improvements: increased airtightness; increased thermal insulation; improving the efficiency of systems such as heating, lighting, and electrical appliances; and installation of renewables such as photovoltaics (Institute for Sustainability & UCL Energy Institute, 2012). The whole-house systems approach to retrofit further considers the interaction between the climate, building site, occupant, and other components of a building (Institute for Sustainability & UCL Energy Institute, 2012). In this way, the building becomes an energy system with interdependent parts that strongly affect one another, and energy performance is considered a result of the whole system activity.

Energy retrofit can be deep, over-time, or partial (Femenías et al., 2018). Deep energy retrofit is considered a onetime event that utilises all available energy saving technologies at that time to reduce energy consumption by 60% - 90% (Fawcett, 2014; Femenías et al., 2018). Over-time retrofit spreads the deep retrofit process out over a strategic period of time, allowing for the integration of future technologies (Femenías et al., 2018). Partial retrofit can also involve several interventions over time but is particularly appropriate to protect architectural works with a high cultural value, retrofitting with the least-invasive energy efficiency measures (Femenías et al., 2018).

Energy retrofit of existing social housing tends to be driven by cost, use of eco-friendly products, and energy savings (Sojkova et al., 2019). Energy savings are particularly important in colder climates where households require greater energy loads for space heating and thermal comfort and are therefore at risk of fuel poverty (Sojkova et al., 2019; Zahiri & Elsharkawy, 2018). Similarly, extremely warm climates requiring high energy loads for air conditioning in the summer can contribute to fuel poverty and will benefit from energy retrofit (Tabata & Tsai, 2020). Femenías et al’s (2018) extensive literature review on property owners’ attitudes to energy efficiency argues that retrofit is typically motivated by other needs, referred to by Outcault et al (2022) as ‘non-energy impacts’ (NEIs). While lists of NEIs are inconsistent in the literature, categories related to “weatherization retrofit” refer to comfort, health, safety, and indoor air quality (Outcault et al., 2022).

Worldwide retrofit schemes such as RetrofitWorks and EnerPHit use varying metrics to define low carbon retrofit, but their universally adopted focus has been on end-point performance targets, which do not include changes to energy using behaviour and practice (Fawcett, 2014). An example of an end-point performance target is Passivhaus’ refurbishment standard (EnerPHit), which requires a heating demand below 25 kWh/(m²a) in cool-temperate climate zones; zones are categorised according to the Passive House Planning Package (PHPP) (Passive House Institute, 2016).

 

References

European Commission. (2021). 2021/0426 (COD) DIRECTIVE OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL on the energy performance of buildings (recast). https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:52021DC0550&from=EN

Fawcett, T. (2014). Exploring the time dimension of low carbon retrofit: Owner-occupied housing. Building Research and Information, 42(4), 477–488. https://doi.org/10.1080/09613218.2013.804769

Femenías, P., Mjörnell, K., & Thuvander, L. (2018). Rethinking deep renovation: The perspective of rental housing in Sweden. Journal of Cleaner Production, 195, 1457–1467. https://doi.org/10.1016/j.jclepro.2017.12.282

Institute for Sustainability, & UCL Energy Institute. (2012). Retrofit strategies. Key Findings: Retrofit project team perspectives. https://www.instituteforsustainability.co.uk/uploads/File/2236_KeySummary03.pdf

Karvonen, A. (2013). Towards systemic domestic retrofit: A social practices approach. Building Research and Information, 41(5), 563–574. https://doi.org/10.1080/09613218.2013.805298

Outcault, S., Sanguinetti, A., Dessouky, N., & Magaña, C. (2022). Occupant Non-Energy Impact Identification Framework: A human-centered approach to understanding residential energy retrofits. Energy and Buildings, 263, 112054. https://doi.org/10.1016/j.enbuild.2022.112054

Passipedia: The Passive House Resource. (n.d.). EnerPHit – the Passive House Certificate for Retrofits. Retrieved 11 April, 2022, from https://passipedia.org/certification/enerphit

Passive House Institute. (2016). Criteria for the Passive House, EnerPHit and PHI Low Energy Building Standard. www.passivehouse.com

RetrofitWorks. (n.d.). RetrofitWorks: Building Energy Efficiency Together. Retrieved 11 April, 2022, from https://retrofitworks.co.uk/

Sojkova, K., Volf, M., Lupisek, A., Bolliger, R., & Vachal, T. (2019). Selection of favourable concept of energy retrofitting solution for social housing in the Czech Republic based on economic parameters, greenhouse gases, and primary energy consumption. Sustainability (Switzerland), 11(22). https://doi.org/10.3390/su11226482

Tabata, T., & Tsai, P. (2020). Fuel poverty in Summer: An empirical analysis using microdata for Japan. Science of the Total Environment, 703. https://doi.org/10.1016/j.scitotenv.2019.135038

Zahiri, S., & Elsharkawy, H. (2018). Towards energy-efficient retrofit of council housing in London: Assessing the impact of occupancy and energy-use patterns on building performance. Energy and Buildings, 174, 672–681. https://doi.org/10.1016/j.enbuild.2018.07.010

 

Created on 23-05-2022 | Update on 20-09-2022

Related definitions

Area: Design, planning and building

Environmental Retrofit Buildings are responsible for approximately 40% of energy consumption and 36% of carbon emissions in the EU (European Commission, 2021). Environmental retrofit, green retrofit or low carbon retrofits of existing homes ais to upgrade housing infrastructure, increase energy efficiency, reduce carbon emissions, tackle fuel poverty, and improve comfort, convenience and aesthetics (Karvonen, 2013). It is widely acknowledged that environmental retrofit should result in a reduction of carbon emissions by at least 60% in order to stabilise atmospheric carbon concentration and mitigate climate change (Fawcett, 2014; Johnston et al., 2005). Worldwide retrofit schemes such as RetrofitWorks, EnerPHit and the EU’s Renovation Wave, use varying metrics to define low carbon retrofit, but their universally adopted focus has been on end-point performance targets (Fawcett, 2014). This fabric-first approach to retrofit prioritises improvements to the building fabric through: increased thermal insulation and airtightness; improving the efficiency of systems such as heating, lighting and electrical appliances; and the installation of renewables such as photovoltaics (Institute for Sustainability & UCL Energy Institute, 2012). The whole-house systems approach to retrofit further considers the interaction between the occupant, the building site, climate, and other elements or components of a building (Institute for Sustainability & UCL Energy Institute, 2012). In this way, the building becomes an energy system with interdependent parts that strongly affect one another, and energy performance is considered a result of the whole system activity. Economic Retrofit From an economic perspective, retrofit costs are one-off expenses that negatively impact homeowners and landlords, but reduce energy costs for occupants over the long run. Investment in housing retrofit, ultimately a form of asset enhancing, produces an energy premium attached to the property. In the case of the rental market, retrofit expenses create a split incentive whereby the landlord incurs the costs but the energy savings are enjoyed by the tenant (Fuerst et al., 2020). The existence of energy premiums has been widely researched across various housing markets following Rosen’s hedonic pricing model. In the UK, the findings of Fuerst et al. (2015) showed the positive effect of energy efficiency over price among home-buyers, with a price increase of about 5% for dwellings rated A/B compared to those rated D. Cerin et al. (2014) offered similar results for Sweden. In the Netherlands, Brounen and Kok (2011), also identified a 3.7% premium for dwellings with A, B or C ratings using a similar technique. Property premiums offer landlords and owners the possibility to capitalise on their  retrofit investment through rent increases or the sale of the property. While property premiums are a way to reconcile          split incentives between landlord and renter, value increases pose questions about long-term affordability of retrofitted units, particularly, as real an expected energy savings post-retrofit have been challenging to reconcile (van den Brom et al., 2019). Social Retrofit A socio-technical approach to retrofit elaborates on the importance of the occupant. To meet the current needs of inhabitants, retrofit must be socially contextualized and comprehended as a result of cultural practices, collective evolution of know-how, regulations, institutionalized procedures, social norms, technologies and products (Bartiaux et al., 2014). This perspective argues that housing is not a technical construction that can be improved in an economically profitable manner without acknowledging that it’s an entity intertwined in people’s lives, in which social and personal meaning are embedded. Consequently, energy efficiency and carbon reduction cannot be seen as a merely technical issue. We should understand and consider the relationship that people have developed in their dwellings, through their everyday routines and habits and their long-term domestic activities (Tjørring & Gausset, 2018). Retrofit strategies and initiatives tend to adhere to a ‘rational choice’ consultation model that encourages individuals to reduce their energy consumption by focusing on the economic savings and environmental benefits through incentive programs, voluntary action and market mechanisms (Karvonen, 2013). This is often criticized as an insufficient and individualist approach, which fails to achieve more widespread systemic changes needed to address the environmental and social challenges of our times (Maller et al., 2012). However, it is important to acknowledge the housing stock as a cultural asset that is embedded in the fabric of everyday lifestyles, communities, and livelihoods (Ravetz, 2008). The rational choice perspective does not consider the different ways that occupants inhabit their homes, how they perceive their consumption, in what ways they interact with the built environment, for what reasons they want to retrofit their houses and which ways make more sense for them, concerning the local context. A community-based approach to domestic retrofit emphasizes the importance of a recursive learning process among experts and occupants to facilitate the co-evolution of the built environment and the communities (Karvonen, 2013). Involving the occupants in the retrofit process and understanding them as “carriers” of social norms, of established routines and know-how, new forms of intervention  can emerge that are experimental, flexible and customized to particular locales (Bartiaux et al., 2014). There is an understanding that reconfiguring socio-technical systems on a broad scale will require the participation of occupants to foment empowerment, ownership, and the collective control of the domestic retrofit (Moloney et al., 2010).

Created on 16-02-2022 | Update on 07-10-2022

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Sustainability

Author: E.Roussou (ESR9)

Area: Community participation

Sustainability is primarily defined as 'the idea that goods and services should be produced in ways that do not use resources that cannot be replaced and that do not damage the environment' (Cambridge Advanced Learner’s Dictionary & Thesaurus, n.d.) and is often used interchangeably with the term “sustainable development”(Aras & Crowther, 2009). As defined by the UN, sustainable development is the effort to “meet the needs of the present without compromising the ability of future generations to meet their own needs” (United Nations, 1987) and is often interpreted as the strategies adopted towards sustainability with the latter being the overall goal/vision (Diesendorf, 2000). Both of these relatively general and often ambiguous terms have been a focal point for the past 20 years for researchers, policy makers, corporations as well as local communities, and activist groups, among others, (Purvis et al., 2019). The ambiguity and vagueness that characterise both of these terms have contributed to their leap into the global mainstream as well as the broad political consensus regarding their value and significance (Mebratu, 1998; Purvis et al., 2019), rendering them one of the dominant discourses in environmental, socio-political and economic issues (Tulloch, 2013). It is, however, highly contested whether their institutionalisation is a positive development. Tulloch, and Tulloch & Nielson (2013; 2014) argue that these terms -as they are currently understood- are the outcome of the “[colonisation of] environmentalist thought and action” which, during the 1960s and 1970s, argued that economic growth and ecological sustainability within the capitalist system were contradictory pursuits. This “colonisation” resulted in the disempowerment of such discourses and their subsequent “[subordination] to neoliberal hegemony” (Tulloch & Neilson, 2014, p. 26). Thus, sustainability and sustainable development, when articulated within neoliberalism, not only reinforce such disempowerment, through practices such as greenwashing, but also fail to address the intrinsic issues of a system that operates on, safeguards, and prioritises economic profit over social and ecological well-being (Jakobsen, 2022). Murray Bookchin (1982), in “The Ecology of Freedom” contends that social and environmental issues are profoundly entangled, and their origin can be traced to the notions of hierarchy and domination. Bookchin perceives the exploitative relationship with nature as a direct outcome of the development of hierarchies within early human societies and their proliferation ever since. In order to re-radicalise sustainability, we need to undertake the utopian task of revisiting our intra-relating, breaking down these hierarchical relations, and re-stitching our social fabric. The intra-relating between and within the molecules of a society (i.e. the different communities it consists of) determines how sustainability is understood and practised (or performed), both within these communities and within the society they form. In other words, a reconfigured, non-hierarchical, non-dominating intra-relationship is the element that can allow for an equitable, long-term setting for human activity in symbiosis with nature (Dempsey et al., 2011, p. 290). By encouraging, striving for, and providing the necessary space for all voices to be heard, for friction and empathy to occur, the aforementioned long-term setting for human activity based on a non-hierarchical, non-dominating intra-relating is strengthened, which augments the need for various forms of community participation in decision-making, from consulting to controlling. From the standpoint of spatial design and architecture, community participation is already acknowledged as being of inherent value in empowering communities (Jenkins & Forsyth, 2009), while inclusion in all facets of creation, and community control in management and maintenance can improve well-being and social reproduction (Newton & Rocco, 2022; Turner, 1982). However, much like sustainability, community participation has been co-opted by the neoliberal hegemony; often used as a “front” for legitimising political agendas or as panacea to all design problems, community participation has been heavily losing its significance as a force of social change (Smith & Iversen, 2018), thus becoming a depoliticised, romanticised prop. Marcus Miessen (2011) has developed a critical standpoint towards what is being labelled as participation; instead of a systematic effort to find common ground and/or reach consensus, participation through a cross-benching approach could be a way to create enclaves of disruption, i.e. processes where hierarchy and power relations are questioned, design becomes post-consensual spatial agency and participation turns into a fertile ground for internal struggle and contestation. Through this cross-benching premise, community participation is transformed into a re-politicised spatial force. In this context, design serves as a tool of expressing new imaginaries that stand against the reproduction of the neoliberal spatial discourse. Thus, sustainability through community participation could be defined as the politicised effort to question, deconstruct and dismantle the concept of dominance by reconfiguring the process of intra-relating between humans and non-humans alike.

Created on 08-06-2022 | Update on 09-06-2022

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Indoor Thermal Comfort

Author: S.Furman (ESR2)

Area: Design, planning and building

Improving indoor thermal comfort is a widely agreed motivate for housing retrofit (Femenías et al., 2018; Outcault et al., 2022; Sojkova et al., 2019; Zahiri & Elsharkawy, 2018). Low carbon retrofit of existing social housing tends to be driven by cost, the use of eco-friendly products, and energy savings (Sojkova et al., 2019). Energy savings are particularly important in colder climates where households require larger energy loads for space heating and thermal comfort and are therefore at greater risk of fuel (energy) poverty (Sojkova et al., 2019; Zahiri & Elsharkawy, 2018). Femenías et al.’s (2018) extensive literature review on property owners’ attitudes to energy efficiency argues that renovations are typically motivated by other needs, referred to by Outcault et al (2022) as ‘non-energy impacts’ (NEIs). While lists of NEIs are inconsistent in the literature, categories related to “weatherization retrofit” (Outcault et al., 2022, p.3) refer to comfort, modernity, health, safety, education, and better indoor air quality (Amann, 2006; Bergman & Foxon, 2020; Broers et al., 2022; Outcault et al., 2022). In poorly maintained social housing, however, the desire to improve indoor air quality and thermal comfort will have an impact on energy consumption. Occupants will, for example, use extra heating to feel comfortable in a damp, mouldy, or cold home. (Zahiri & Elsharkawy, 2018).   There are three main technical improvements to low carbon retrofit: (1) enhancing the building fabrics thermal properties; (2) improving systems efficiency; and (3) renewable energy integration (Institute for Sustainability & UCL Energy Institute, 2012). In order for the Passivehaus Institut’s EnerPHit Retrofit Plan to meet Passivhaus standards for indoor air quality, homes must achieve high levels of air tightness complemented by a mechanical ventilation system including heat recovery (MVHR). Specifically, “airtightness of a building must achieve an air change per hour rate of less than 0.6 at 50 Pa of pressure (n50), and have ventilation provided by either a balanced mechanical heat recovery ventilation or demand-controlled ventilation systems” (McCarron et al., 2019, p.297). This airtightness concept is revered for saving energy, avoiding structural damage, and contributing to thermal comfort (Bastian et al., 2022) while requiring no natural ventilation such as open windows. Mechanical HVAC units alter indoor air temperature, air movement, ventilation, noise levels, and humidity (Outcault et al., 2022). But despite known benefits to physical health and clean air, this may not lead to optimum user-comfort. This is because social housing residents have unique housing needs that differ from homeowners (Sunikka-Blank et al., 2018) and cannot be predicted without resident engagement, as residents are experts in the way they live and use their homes (Boess, 2022; Gianfrate et al., 2017; Walker et al., 2014).   Post Occupancy Evaluation after retrofit has found that social housing residents are often unfamiliar with mechanical systems and their sustainable benefits, especially when retrofit occurs without resident input (Garnier et al., 2020). This can lead to misuse, overheating, the prebound effect, and the rebound effect where affordable energy bills lead to excessive heating—at times 25-26°C (Zoonnekindt, 2019)—contributing to performance gaps as high as five times the predicted energy consumption (Traynor, 2019). Other households considered mechanical systems to be bulky, ugly, and noisy, prompting removal, lack of use, and at times emotional distress (Lowe et al., 2018). DREEAM’s Berlin pilot site found one household blocking mechanical ventilation with tissue paper because they considered the air too cold and residents “haven’t been informed about the positive impact of a well working ventilation on their health and on the energy efficiency of the heating in their apartment” (Zoonnekindt, 2019). DREEAM continued the project with Green Neighbours (Zoonnekindt, 2019), an innovative engagement program co-designed with and for residents to better inform mechanical systems usage. However, literature shows (Boess, 2022; Gianfrate et al., 2017; Walker et al., 2014) that informing residents on how to use mechanical systems is unlikely to change use-habits or adequately combat performance gaps. In order to change residents’ energy behaviours, resident stakeholders should be integrated in retrofit decision-making.

Created on 20-09-2022 | Update on 01-12-2023

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Life Cycle Costing

Author: A.Elghandour (ESR4)

Area: Design, planning and building

Life Cycle Costing (LCC) is a method used to estimate the overall cost of a building during its different life cycle stages, whether from cradle to grave or within a predetermined timeframe (Nucci et al., 2016; Wouterszoon Jansen et al., 2020). The Standardised Method of Life Cycle Costing (SMLCC) identifies LCC in line with the International Standard ISO 15686-5:2008 as "Methodology for the systematic economic evaluation of life cycle costs over a period of analysis, as defined in the agreed scope." (RICS, 2016). This evaluation can provide a useful breakdown of all costs associated with designing, constructing, operating, maintaining and disposing of this building (Dwaikat & Ali, 2018). Life cycle costs of an asset can be divided into two categories: (1) Initial costs, which are all the costs incurred before the occupation of the house, such as capital investment costs, purchase costs, and construction and installation costs (Goh & Sun, 2016; Kubba, 2010); (2) Future costs, which are those that occur after the occupancy phase of the dwelling. The future costs may involve operational costs, maintenance, occupancy and capital replacement (RICS, 2016). They may also include financing, resale, salvage, and end-of-life costs (Karatas & El-Rayes, 2014; Kubba, 2010; Rad et al., 2021). The costs to be included in a LCC analysis vary depending on its objective, scope and time period. Both the LCC objective and scope also determine whether the assessment will be conducted for the whole building, or for a certain building component or equipment (Liu & Qian, 2019; RICS, 2016). When LCC combines initial and future costs, it needs to consider the time value of money (Islam et al., 2015; Korpi & Ala-Risku, 2008). To do so, future costs need to be discounted to present value using what is known as "Discount Rate" (Islam et al., 2015; Korpi & Ala-Risku, 2008). LCC responds to the needs of the Architectural Engineering Construction (AEC) industry to recognise that value on the long term, as opposed to initial price, should be the focus of project financial assessments (Higham et al., 2015). LCC can be seen as a suitable management method to assess costs and available resources for housing projects, regardless of whether they are new or already exist. LCC looks beyond initial capital investment as it takes future operating and maintenance costs into account (Goh & Sun, 2016). Operating an asset over a 30-year lifespan could cost up to four times as much as the initial design and construction costs (Zanni et al., 2019). The costs associated with energy consumption often represent a large proportion of a building’s life cycle costs. For instance, the cumulative value of utility bills is almost half of the cost of a total building life cycle over a 50-year period in some countries (Ahmad & Thaheem, 2018; Inchauste et al., 2018). Prioritising initial cost reduction when selecting a design alternative, regardless of future costs, may not lead to an economically efficient building in the long run (Rad et al., 2021). LCC is a valuable appraising technique for an existing building to predict and assess "whether a project meets the client's performance requirements" (ISO, 2008). Similarly, during the design stages, LCC analysis can be applied to predict the long-term cost performance of a new building or a refurbishing project (Islam et al., 2015; RICS, 2016). Conducting LCC supports the decision-making in the design development stages has a number of benefits (Kubba, 2010). Decisions on building programme requirements, specifications, and systems can affect up to 80% of its environmental performance and operating costs (Bogenstätter, 2000; Goh & Sun, 2016). The absence of comprehensive information about the building's operational performance may result in uninformed decision-making that impacts its life cycle costs and future performance (Alsaadani & Bleil De Souza, 2018; Zanni et al., 2019). LCC can improve the selection of materials in order to reduce negative environmental impact and positively contribute to resourcing efficiency (Rad et al., 2021; Wouterszoon Jansen et al., 2020), in particular when combined with Life Cycle Assessment (LCA). LCA is concerned with the environmental aspects and impacts and the use of resources throughout a product's life cycle (ISO, 2006). Together, LCC and LCA contribute to adopt more comprehensive decisions to promote the sustainability of buildings (Kim, 2014). Therefore, both are part of the requirements of some green building certificates, such as LEED (Hajare & Elwakil, 2020).     LCC can be used to compare design, material, and/or equipment alternatives to find economically compelling solutions that respond to building performance goals, such as maximising human comfort and enhancing energy efficiency (Karatas & El-Rayes, 2014; Rad et al., 2021). Such solutions may have high initial costs but would decrease recurring future cost obligations by selecting the alternative that maximises net savings (Atmaca, 2016; Kubba, 2010; Zanni et al., 2019). LCC is particularly relevant for decisions on energy efficiency measures investments for both new buildings and building retrofitting. Such investments have been argued to be a dominant factor in lowering a building's life cycle cost (Fantozzi et al., 2019; Kazem et al., 2021). The financial effectiveness of such measures on decreasing energy-related operating costs, can be investigated using LCC analysis to compare air-condition systems, glazing options, etc. (Aktacir et al., 2006; Rad et al., 2021). Thus, LCC can be seen as a risk mitigation strategy for owners and occupants to overcome challenges associated with increasing energy prices (Kubba, 2010). The price of investing in energy-efficient measures increase over time. Therefore, LCC has the potential to significantly contribute to tackling housing affordability issues by not only making design decisions based on the building's initial costs but also its impact on future costs – for example energy bills - that will be paid by occupants (Cambier et al., 2021). The input data for a LCC analysis are useful for stakeholders involved in procurement and tendering processes as well as the long-term management of built assets (Korpi & Ala-Risku, 2008). Depending on the LCC scope, these data are extracted from information on installation, operating and maintenance costs and schedules as well as the life cycle performance and the quantity of materials, components and systems, (Goh & Sun, 2016) These information is then translated into cost data along with each element life expectancy in a typical life cycle cost plan (ISO, 2008). Such a process assists the procurement decisions whether for buildings, materials, or systems and/or hiring contractors and labour, in addition to supporting future decisions when needed (RICS, 2016). All this information can be organised using Building Information Modelling (BIM) technology (Kim, 2014; RICS, 2016). BIM is used to organise and structure building information in a digital model. In some countries, it has become mandatory that any procured project by a public sector be delivered in a BIM model to make informed decisions about that project (Government, 2012). Thus, conducting LCC aligns with the adoption purposes of BIM to facilitate the communication and  transfer of building information and data among various stakeholders (Juan & Hsing, 2017; Marzouk et al., 2018). However, conducting LCC is still challenging and not widely adopted in practice. The reliability and various formats of building related-data are some of the main barriers hindering the adoption of LCCs (Goh & Sun, 2016; Islam et al., 2015; Kehily & Underwood, 2017; Zanni et al., 2019).

Created on 05-12-2022 | Update on 20-05-2023

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Performance Gap in Retrofit

Author: S.Furman (ESR2)

Area: Design, planning and building

The performance gap in retrofit refers to the disparity between the predicted and actual energy consumption after a retrofit project, measured in kWh/m2/year. This discrepancy can be substantial, occasionally reaching up to five times the projected energy usage (Traynor, 2019). Sunikka-Blank & Galvin (2012) identify four key factors as contributing to the performance gap: (1) the rebound effect, (2) the prebound effect, (3) interactions of occupants with building components, and (4) the uncertainty of building performance simulation outcomes. Gupta & Gregg (2015) additionally identify elevated building air-permeability rates as a factor leading to imbalanced and insufficient extract flowrates, exacerbating the performance gap. While post occupancy evaluation of EnerPhit—the Passivhaus Institut certification for retrofit—has shown far better building performance in line with predictions, the human impact of building users operating the building inefficiently will always lead to some sort of performance gap (Traynor, 2019, p. 34). Deeper understanding of the prebound effect and the rebound effect can improve energy predictions and aid in policy-making (Galvin & Sunikka-Blank, 2016). Therefore, the ‘prebound effect’ and the ‘rebound effect’, outlined below, are the most widely researched contributors to the energy performance gaps in deep energy retrofit.   Prebound Effect The prebound effect manifests when the actual energy consumption of a dwelling falls below the levels predicted from energy rating certifications such as energy performance certificates (EPC) or energy performance ratings (EPR). According to Beagon et al. (2018, p.244), the prebound effect typically stems from “occupant self-rationing of energy and increases in homes of inferior energy ratings—the type of homes more likely to be rented.” Studies show that the prebound effect can result in significantly lower energy savings post-retrofit than predicted and designed to achieve (Beagon et al., 2018; Gupta & Gregg, 2015; Sunikka-Blank & Galvin, 2012). Sunikka-Blank & Galvin’s (2012) study compared the calculated space and water heating energy consumption (EPR) with the actual measured consumption of 3,400 German dwellings and corroborated similar findings of the prebound effect in the Netherlands, Belgium, France, and the UK. Noteworthy observations from this research include: (1) substantial variation in space heating energy consumption among dwellings with identical EPR values; (2) measured consumption averaging around 30% lower than EPR predictions; (3) a growing disparity between actual and predicted performance as EPR values rise, reaching approximately 17% for dwellings with an EPR of 150 kWh/m²a to about 60% for those with an EPR of 500 kWh/m²a (Sunikka-Blank & Galvin, 2012); and (4) a reverse trend occurring for dwellings with an EPR below 100 kWh/m²a, where occupants consume more energy than initially calculated in the EPR, referred to as the rebound effect. Galvin & Sunikka-Blank (2016) identify that a combination of high prebound effect and low income is a clear indicator of fuel poverty, and suggest this metric be utilised to target retrofit policy initiatives.   Rebound Effect The rebound effect materializes when energy-efficient buildings consume more energy than predicted. Occupants perceive less guilt associated with their energy consumption and use electrical equipment and heating systems more liberally post-retrofit, thereby diminishing the anticipated energy savings (Zoonnekindt, 2019). Santangelo & Tondelli (2017) affirm that the rebound effect arises from occupants’ reduced vigilance towards energy-related behaviours, under the presumption that enhanced energy efficiency in buildings automatically decreases consumption, regardless of usage levels and individual behaviours. Galvin (2014) further speculates several factors contributing to the rebound effect, including post-retrofit shifts in user behaviour, difficulties in operating heating controls, inadequacies in retrofit technology, or flawed mathematical models for estimating pre- and post-retrofit theoretical consumption demand. The DREEAM project, funded by the European Union, discovered instances of electrical system misuse in retrofitted homes upon evaluation (Zoonnekindt, 2019). A comprehensive comprehension of the underlying causes of the rebound effect is imperative for effective communication with all retrofit stakeholders and for addressing these issues during the early design stages.   Engaging residents in the retrofit process from the outset can serve as a powerful strategy to mitigate performance gaps. Design-thinking (Boess, 2022), design-driven approaches (Lucchi & Delera, 2020), and user-centred design (Awwal et al., 2022; van Hoof & Boerenfijn, 2018) foster socially inclusive retrofit that considers Equality, Diversity, and Inclusion (EDI). These inclusive approaches can increase usability of technical systems, empower residents to engage with retrofit and interact with energy-saving technology, and enhance residents’ energy use, cultivating sustainable energy practices as habitual behaviours. Consequently, this concerted effort not only narrows the performance gap but simultaneously enhances overall wellbeing and fortifies social sustainability within forging communities.

Created on 08-09-2023 | Update on 01-12-2023

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Related case studies

Related publications

Awwal, S., Soliman-Junior, J., Ayo-Adejuyigbe, M., Tzortzopoulos, P., & Kagioglou, M. (2022). Social Housing Retrofit Living Lab: Methodological Approach. IOP Conference Series: Earth and Environmental Science, 1101(5), 052020. https://doi.org/10.1088/1755-1315/1101/5/052020

Boess, S. (2022). Let’s Get Sociotechnical: A Design Perspective on Zero Energy Renovations. Urban Planning, 7(2), 97–107. https://doi.org/10.17645/up.v7i2.5107

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