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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 23-10-2024

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 23-10-2024

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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 23-10-2024

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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 23-10-2024

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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 23-10-2024

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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 23-10-2024

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Prebound Effect

Author: T.Croon (ESR11)

Area: Design, planning and building

The concept ‘prebound effect’ refers to the phenomenon where actual energy consumption in buildings is significantly lower than the calculated energy consumption needed to maintain comfortable indoor temperatures (Sunikka-Blank & Galvin, 2012). This is typically observed in older, less energy-efficient homes, where occupants often under-heat their homes due to financial constraints, leading to lower actual energy usage than predicted by models (Galvin & Sunikka-Blank, 2016). This contrasts with the more commonly used term ‘rebound effect’, which occurs when energy consumption increases following efficiency improvements, offsetting some of the anticipated savings (Teli et al., 2015). The difference between the two is clearly visualised in Figure 1, developed by Sunikka-Blank and Galvin (2012). Energy savings discrepancies The prebound effect leads to significant discrepancies in energy savings estimates for retrofitting projects. Standard models often overestimate energy savings because they do not account for the lower baseline consumption caused by the prebound effect. This discrepancy is crucial because it implies that thermal retrofits may not yield the anticipated reductions in energy use and carbon emissions, which are often overstated in policy and financial analyses (Galvin, 2023). A detailed explanation of the performance gap is available in the vocabulary entry by Furman (2024). For instance, in Hungary, research shows that energy consumption predictions are often based on technical data alone, ignoring actual under-consumption behaviours, leading to overestimates in expected savings (Gróf et al., 2022). Similarly, in Italy, studies have highlighted that prebound effects cause a gap between theoretical energy models and actual energy usage, complicating the accurate forecasting of energy savings from retrofits (Giuliani et al., 2016). The study by Van den Brom et al. (2019) also supports this, showing that building characteristics and occupant behavior significantly influence energy consumption, with discrepancies between expected and actual savings due to prebound effects being notable in both the Netherlands and Denmark. Additionally, Gróf et al. (2022) emphasised that the prebound effect is influenced by the financial status of households, with households having limited financial means more likely to under-heat their homes, resulting in a greater prebound effect and further complicating the prediction of energy savings. Inherently linked to energy poverty Therefore, the prebound effect is closely linked to energy poverty, as it often reflects the behaviour of households that cannot afford to heat their homes adequately. Households experiencing fuel poverty are more likely to exhibit high prebound effects due to their efforts to save money on heating (Galvin & Sunikka-Blank, 2016). For instance, social housing tenants in the UK showed significant prebound effects, leading to under-heated homes and reduced energy consumption prior to retrofitting (Teli et al., 2015). Addressing the prebound effect involves recognising and mitigating the financial constraints that lead to under-consumption, thus improving both the accuracy of energy savings predictions and the living conditions of households experiencing energy poverty (Galvin, 2024a, 2024b). Moreover, hidden energy poverty is a critical aspect of this issue. Households often are not categorised as energy poor based on expenditure-based indicators because they do not dare to put their heating on due to financial constraints (Cong et al., 2022; Eisfeld & Seebauer, 2022). These households minimise their heating to the point where their energy expenditures are deceptively low, masking the severity of their situation. However, more recent indicators that focus on energy efficiency rather than high costs would identify them as energy poor (Betto et al., 2020). Addressing hidden energy poverty requires a shift in assessment criteria, also focusing on the energy efficiency of homes rather than just the high cost of energy bills. This approach ensures that households struggling with inadequate heating due to financial constraints are accurately identified and supported (Croon et al., 2023).

Created on 20-06-2024 | Update on 23-10-2024

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Housing Quality

Author: A.Elghandour (ESR4)

Area: Design, planning and building

Housing quality is concerned with the conditions and characteristics ensuring it is safe, healthy, comfortable, and sustainable for its occupants. It considers the physical conditions of a dwelling and the social and physical environment surrounding it (Bonnefoy, 2007; Swope & Hernández, 2019). There is increasing pressure to ensure affordable housing meets quality standards in Europe and the UK. Neglecting quality in assessing affordability could perpetuate poor-quality, unsustainable housing, harming both the planet and households' wellbeing (AHC, 2019; Fraser et al., 2023; Haffner & Heylen, 2011; OECD, 2021). This vocabulary entry focuses on housing quality.   Housing quality directly impacts the wellbeing of households by influencing physical and mental health and financial stability. It has been recognised as a crucial determinant of health and wellbeing, as poor housing conditions are linked to numerous health issues, including respiratory and cardiovascular diseases, injuries, and mental health disorders (WHO, 2018). As such, housing quality not only concerns the physical attributes of a dwelling but also its capacity to support the health and wellbeing of its occupants​ (Rolfe et al., 2020).     Levels of Housing Quality   Housing quality can be recognised through various contextual levels, which include:   Physical structures and features of buildings, such as insulation, ventilation systems, materials used, and essential services such as heating, plumbing, and electrical systems (Keall et al., 2010). Internal environment and living conditions, which refer to the atmosphere within a dwelling. These include air quality, light, noise levels, and thermal comfort, all contributing to indoor environmental quality. They could also encompass factors such as overcrowding and cleanliness (Riva et al., 2022). The living conditions arise from the interaction between the building characteristics and the residents, and how they use or treat the dwelling. (Bonnefoy, 2007; Riva et al., 2022). For example, mould can develop due to a lack of proper ventilation systems suitable for the household and dwelling size. Alternatively, a proper ventilation system might be provided; however, occupants may not use it when cooking, bathing or showering (Keall et al., 2010). Household characteristics refer to the behaviours and lifestyles of residents. According to Keall et al. (2010, p. 767), the household level encompasses "social, cultural and economic aspects such as affordability, suitability, security of tenure,” which impact people's needs for space, energy, water, and transport. Additionally, it acknowledges that demographic, psychological, and biological aspects, such as attitudes towards recycling, maintenance, cleaning routines, and use of space, influence lifestyles. External community and infrastructure involve the neighbourhood, regional policies, and global environmental conditions impacting housing quality. Factors such as urban planning decisions, availability of community resources, and neighbourhood safety play crucial roles (Keall et al., 2010; Swope & Hernández, 2019). Regulatory and policy frameworks pertain to the standards and regulations to ensure housing quality. Compliance with these regulations should promote equity in housing practices (Swope & Hernández, 2019). For example, A new set of Consumer Standards established by the Regulator of Social Housing in England aims to improve the quality of social housing and ensure that landlords fulfill their responsibilities to tenants by providing quality homes, transparent operations, and fair tenancy management (Regulator of Social Housing, 2024).     Housing Quality Indicators   Housing quality indicators are vital for assessing the conditions of dwellings. They could address various aspects of housing, such as safety, sustainability, comfort, and suitability for residents. These indicators are essential for understanding the physical state of housing and the living conditions within dwellings. These indicators could serve four purposes:   Measuring housing quality and affordability across countries: Some housing quality indicators could enable meaningful cross-country comparisons to better determine what residents are paying for in terms of quality. The OECD (2021) Policy Brief on Affordable Housing highlighted some housing quality measures to accompany measuring housing affordability, such as the "Overcrowding Rate," "Housing Deprivation Rate," and subjective measures to assess housing affordability and quality based on household perceptions. Elaboration on these measures is available in the Measuring Housing Affordability vocabulary.   Measuring housing quality within a country: Some indicators are used to evaluate the quality of housing schemes to ensure that housing standards are met across different regions. For example, non-decent housing in England is identified with the help of the Housing Health and Safety Rating System (HHSRS) (Department for Communities and Local Government, 2006). HHSRS assesses 29 potential health and safety hazards in residential properties, including structural dangers, toxicity, mould and inadequate heating. Another example is England's Housing Quality Indicators (HQIs) system. Although currently withdrawn, it served as an assessment tool to evaluate housing scheme quality. The HQIs system encompassed four categories: location and proximity to amenities, site-related aspects (landscaping, open spaces, pathways), housing unit features (noise, lighting, accessibility, sustainability), and the external environment (Homes and Communities Agency, 2011).   Measuring housing satisfaction across groups:  Other indicators measure household satisfaction, gauging how well housing meets their expectations and needs. For example, the English Housing Survey (EHS) collects comprehensive data on housing conditions and residents' satisfaction levels across different demographic groups and regions (DLUHC, 2019). It evaluates housing quality, adequacy of amenities, safety measures, and overall satisfaction with the living environment. Thus, it enables identifying targeted improvements needed within the housing sector.   Measuring housing quality of a specific housing scheme: Post-Occupancy Evaluation (POE) could be considered a housing quality indicator in the design and construction context. POE is a process for assessing buildings' performance and functionality after they have been occupied (Hadjri & Crozier, 2009). It could include energy efficiency, indoor environmental quality, and occupant satisfaction (Elsayed et al., 2023). The evaluation involves various methodologies to collect data, which can be objective (measured data) and subjective (occupant feedback), providing insights that could lead to improvements in management practices and future designs. However, in the EU context, this process remains inconsistent (Elsayed et al., 2023). This inconsistency hinders comparing results and gathering insights to improve broader housing quality.   Despite the usefulness of the indicators mentioned above, accurately measuring housing quality is still challenging. The inherent subjectivity of what constitutes "adequate" housing means that perceptions can vary significantly due to influences of cultural, economic, and individual expectations. Furthermore, the technical feasibility of employing comprehensive quality indicators is often limited by outdated or incomplete data on the characteristics of dwellings. These limitations hinder effective housing quality assessment, making it difficult to enforce and update housing standards consistently (OECD, 2021).

Created on 14-10-2024 | Update on 23-10-2024

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Techno-optimism

Author: S.Furman (ESR2)

Area: Design, planning and building

Techno-optimism refers to the belief that advances in technology will improve humanity, enhance quality of life, and solve critical problems including climate change, health issues and social inequality (Danaher, 2022). According to Danaher (2022), techno-optimism assumes technology will ensure “the good does or will prevail over the bad” (p.54). Techno-optimists believe that technological innovation is a key driver for economic growth and can provide solutions to many of the pressing challenges faced by contemporary society (Wilson, 2017). Keary (2016) links faith in technological optimism to an unshakable commitment to economic growth. Technological change modelling (TCM), he argues, has shifted the terms of environmental debate, pulling efforts away from ‘green’ ecologism (associated with degrowth movements), and toward techno-optimism; a belief that mitigation pathways should rely on technological advancements. Techno-optimism emerges from enlightenment ideals, whereby reason and scientific progress are seen as pathways to improving human conditions and capabilities by overcoming “existential risk” (Bostrom, 2002) through technological advancements (Wilson, 2017). Hornborg (2024) criticises techno-optimism for its failure to address ecological and social inequalities exacerbated by technology. Further, technological solutions often address symptoms rather than root causes, leading to a superficial treatment of complex problems (Wilson, 2017).  Hornborg, using Marx’s commodity fetishism and World Systems Theory as his guide (Marx, 1990), seeks to unmask modern assumptions about what technology is. Both capitalists and certain left-wing thinkers exalt technology, viewing it as embodying human progress — a promethean mode of thinking. This overlooks, however, the social relations and material, energetic, and metabolic flows needed to maintain technological systems. Technology needs a “sociometabolic reconceptualization” (Hornborg, 2024, p. 28). Historically, technological progress in the world’s industrial core, was dependent on unequal social relations and colonial patterns of extraction from non-industrial peripheries. Shifting to green technologies, in Horrnborg’s view, will involve repeating these inequities: sugar-ethanol, or electric powered cars, for instance, will rely on exploited land in Brazil and the cobalt-rich Congo. “High tech cores versus their exploited peripheries” (Hornborg, 2024, p. 38), recasts the colonial industrial core-periphery dynamic (Wolf et al., 2010), exacerbating ecological and social inequalities. By attributing too much power to technology itself, techno-optimists may neglect the need for conscious and deliberate governance of technological change (Bostrom, 2002, p. 11). Further, it is crucial to maintain a balanced perspective that recognises both the opportunities and the limitations of technological advancements (Wilson, 2017). Social, political, and cultural contexts must shape technological outcomes. Danaher (2022) argues through collective effort, it is possible to create the right institutions and frameworks to guide technological development towards beneficial ends. Technological innovation plays a key role in deep energy retrofit (DER), which relies on three main technical improvements to reach end point performance targets, measured in kWh/m2/year: increased thermal insulation and airtightness; 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). Techno-optimism in DER has led to the widespread adoption of ground source and air source heat pumps, such as mechanical heat and ventilation systems (MVHR) (Traynor, 2019), to mechanically stabalise indoor air temperatures (Outcault et al., 2022), LED lighting smart systems (Bastian et al., 2022), and upgraded systems for heating and hot water (Roberts, 2008). There are many concerns with techno-optimism in DER: (1) the gap between predicted and actual energy performance can reach as high as five times the prediction (Traynor, 2019), (2) the adoption of techno-optimism does not consider the certainty of technological obsolescence, (3) inoperable windows due to mechanical heating and ventilation increases the risk of future overheating, and cooling costs, and (4) DER disregards architectural vernacular and passive energy strategies, including cross ventilation, thermal mass, and solar gains. In social housing retrofit, non-energy benefits including comfort, modernity, health, and safety, (Amann, 2006; Bergman & Foxon, 2020; Broers et al., 2022)—negated in techno-optimism—are often more important to social housing residents than energy-related benefits. Further, technological innovation in retrofit is often tested on social housing (Morgan et al., 2024), despite housing tenants from marginalised groups, to convince private markets to adopt technologies.

Created on 14-10-2024 | Update on 07-11-2024

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Thermal Insulation & Airtightness

Author: S.Furman (ESR2)

Area: Design, planning and building

Increasing the thermal properties of the building envelope is a passive strategy to reduce energy loss and ensure significant reductions in energy demand (Grecchi, 2022). Van den Brom et al (2019) define thermal renovation as “renovation measures that are taken to reduce energy consumption used for thermal comfort”, and group thermal insulation, airtightness and efficient electrical system into a single category. Accordingly, deep ‘thermal’ renovation occurs when significant improvement in at least three building components bring thermal performance to a level equal to or higher than the current building regulation standards (van den Brom et al., 2019). These building components include roof insulation, floor insulation, façade insulation, window improvements, heating system, domestic hot water system, and ventilation system (van den Brom et al., 2019). Other authors (Institute for Sustainability & UCL Energy Institute, 2012; Sojkova et al., 2019; Traynor, 2019) divide electrical systems into a further category for clearer practical application. The concept of airtightness is revered for saving energy, avoiding structural damage, contributing to thermal comfort (Bastian et al., 2022), and is key to reducing heat loss through ventilation (Roberts, 2008). Draught proofing involves draught-stripping, replacing leaky windows and closing off unused chimneys (Roberts, 2008). The location of an airtight layer should be identified, and all penetrations through it minimised, sealed, and recorded (Traynor, 2019). This airtight layer can be airtight board, a plastered wall, or a membrane with appropriate tape at all junctions such as window openings (Traynor, 2019). Triple-glazed windows in combination with any frame material are the most efficient glazing system at reducing primary energy cost and CO₂ emissions (Sojkova et al., 2019). All air pockets should be sealed to prevent draughts and thermal bridging. Thermal bridging should be eliminated wherever possible, although a comprehensive thermal reduction with low internal surface temperatures can prevent physical problems such as moisture and mould (Bastian et al., 2022). There are many forms of insulation to consider during retrofit that considerably contribute to a reduction in heat loss. Filling external cavity walls with insulation can reduce heat loss through walls by up to 40% (Roberts, 2008). Ground floor insulation and roof insulation are also necessary steps in DER (Grecchi, 2022; Roberts, 2008; Traynor, 2019). Ground floor insulation can occur in suspended timber floors between joists or above solid concrete floors (Traynor, 2019). Roof insulation can be added between structural elements, or using a ‘cold’ roof solution, with insulation laid or sprayed over the existing ceiling (Traynor, 2019). Alternatively, green roofs can reduce the amount of heat penetration through roofs, playing a similar role to roof insulation. This is done by absorbing heat into their thermal mass alongside the evaporation of moisture but will require structural upgrades to manage the new load (Roberts, 2008). External wall insulation (EWI) protects the building fabric, improves airtightness and is relatively quick and easy to install (Roberts, 2008). EWI can also help mitigate overheating by absorbing less heat than the original material, while allowing existing thermal mass from solid masonry walls and concrete to be retained within the insulated envelope (Bastian et al., 2022). The two main external insulation systems are ventilated rainscreen systems and rendered insulation systems (Roberts, 2008). EWI is inappropriate for historical building use because it will cover the historical architectural character. Gupta & Gregg’s (2015) preserved the original exterior façade by using internal wall insulation inside the front façade and EWI on all other façades. However, drawbacks to this solution can include the loss of internal floor area, and reduced energy efficiency as notable heat loss can occur where the internal insulated wall meets the external insulated wall (Gupta & Gregg, 2015).

Created on 25-10-2024 | Update on 08-11-2024

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