Barriers to Low and Zero carbon homes
The following section highlights some of the key barriers to the diffusion of LZC new build and retrofit in the UK. Although many of the issues are fairly consistent between both new build and retrofit, where innovation and adoption faces similar barriers, there are a number of areas where the challenges diverge. These barriers are associated with concerns over the economic benefits, technical challenges and shortfalls and the cultural and behaviour attitudes that may inhibit the transition to a predominantly low energy building regime.
The following section includes a discussion of the range of barriers identified in the academic literature, as presenting key obstacles to the further diffusion of low carbon retrofit in the UK housing stock. This includes reference to policy interventions as identified in and to what extent these initiatives have addressed these barriers.
Quality, skills, performance and rebound issues
A review of much of the literature surrounding deep retrofit does highlight some technical and implementation issues surrounding low energy retrofit innovations. With some describing poor technical performance of materials, and a lack of available products; with many needing to be imported from abroad (TSB, 2014, Heffernan et al., 2015, Dowson et al., 2012, Osmani and O’Reilly, 2009). Although many involved in the Retrofit for the future project, have described how they will create new supply chains, for some of the new materials products and processes as a result of the project.
Another consistent theme is the lack of available skilled workforce and knowledge base for undertaking retrofit works. This large scale dearth of a trained workforce, and familiarity with some of the fairly unorthodox approaches used in low energy retrofit, is described as a consistent barrier to the adoption of novel technologies and solutions. Many of the measures in the Retrofit for the future project were new to the site teams and 22 projects identified lack of skills as a key challenge (TSB, 2014). However it is clear that increasing demand drivers such as ECO and the Green Deal, and their successors will be crucial in building capacity in these areas. Hopefully along with greater experience and familiarity, the cultural attitudes within the industry will become increasingly positive to these new techniques and approaches.
There is a large body of research into a phenomenon known as the ‘performance gap’, whereby modelled reductions in energy and CO2 are much greater than post occupancy measurement. Indeed Lowe and Oreszczyn (2008) describe how the energy performance of the UK housing stock may be historically over optimistically estimated. Many studies involving post occupancy assessment have shown that buildings; particularly those that have been retrofitted do not deliver the estimated energy savings using the statutory assessment methodology; UK SAP. During a detailed monitoring study of the Warm Front Scheme Hong et al. (2006) estimated a 49% reduction of fuel consumption as modelled, however actual monitoring following the refurbishment showed that only 10–17% energy savings were achieved.
Sorrell et al. (2009) characterise the cause of these gaps relating to three distinct but interrelated issues:
Shortfall, the difference between actual savings in energy consumption and those expected on the basis of engineering estimates
Temperature take-back, the change in mean internal temperatures following the energy efficiency improvement, or the reduction in energy savings associated with that change; and
Behavioural change, the proportion of the change in internal temperature that derives from adjustments of heating controls and other variables by the user (e.g. opening windows), or the reduction in energy savings associated with those changes
The first of these issues ‘Shortfall’ can also be divided into two further categories; the paucity of models to reflect the actual conditions of the building and the environment, secondly the quality or performance of the physical interventions or measures. The standardised methodology for assessing a buildings performance and producing EPCs is RdSAP, and SAP. The method is criticised for attempting to estimate the cost-effective performance of a building, and thus create perverse incentives that may lead to additional CO2 emissions (Kelly et al., 2012). Many also argue that the method makes overly optimistic assumptions, and that a method that places greater focus on heat loads and losses might be more suitable (McLeod et al., 2012).
Secondly the issues surrounding poor installation quality have been a significant focus for regulatory initiatives such as the Microgeneration certification scheme (MCS), as well as membership bodies such as the Federation of Master Builders (FMB), National Insulation Association (NIA), SWIGA -the Solid Wall Insulation Guarantee Agency and the Green Deal Installer scheme. Notwithstanding these quality assurance organisations, many studies have reported many experiences of poor quality and faulty installations across government insulation schemes (Walker et al., 2014).
Walker et al. (2014) highlight 4 important characteristics of successful retrofit; competence, convenience, technology quality and minimised disruption. It can be seen how problems relating to poor quality installations can become a particularly damaging barrier to the increased uptake of retrofit measures, particularly if receiving media attention. Owen et al. (2014) also highlight the difficulty in regulation and policy interventions, in a sector characterised by many small organisations and sole traders.
Consideration of direct temperature take back effects can be characterised as rebound effects. In a comprehensive review of data on the subject Sorrell et al. (2009) estimate that direct rebound effects for domestic heating measures are in the region of 30%. Although these effects can be seen to have benefits to occupants in terms of improved warmth and associated health benefits, it is important to factor these effects into assessments of mitigation potential.
However, using the standardised SAP methodology takes no account of these effects, as it assumes the occupants use whatever energy necessary to maintain an internal temperature of approximately 21 degrees centigrade (BRE, 2014). This has important implications for retrofit schemes particularly, those involving the Green Deal. Given that the green deal makes assumptions based on this optimised temperature profile, many homes that are maintaining a lower internal temperature, may see energy costs rise significantly with green deal repayments, as observed by (Gupta and Chandiwala, 2010).
Not all studies have shown significant performance gaps, with a large 49,000 home pilot Weber et al study shows impacts of retrofit have been 1.2–1.7 times higher than predicted (Webber et al., 2015). The study attempted to isolate the impact of the measures installed from weather data and population changes; however it is much more difficult to account for the variation of individual behaviour in such modelling studies.
It can be argued that these range of issues surrounding the performance of retrofit interventions, may further inhibit the diffusion of innovations in the sector, creating negative perceptions of undergoing efficiency retrofit. The issues surrounding the behavioural component of retrofit will be discussed in the following section.
BRE 2014. The Government’s Standard Assessment Procedure for Energy Rating of Dwellings 2012. Watford: Building Research Establishment.
DOWSON, M., POOLE, A., HARRISON, D. & SUSMAN, G. 2012. Domestic UK retrofit challenge: Barriers, incentives and current performance leading into the Green Deal. Energy Policy, 50, 294-305.
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HONG, S. H., ORESZCZYN, T. & RIDLEY, I. 2006. The impact of energy efficient refurbishment on the space heating fuel consumption in English dwellings. Energy and Buildings, 38, 1171-1181.
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TSB 2014. Retrofit for the future – A guide to making retrofit work. Swindon: Technology Strategy Board.
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