Aplicaciones con nanoestructuras

First proposed by the Labour Government in 2004 (ODPM, 2004), the Code for Sustainable Homes (CSH or the Code), formed part of UK policy response to meet the UK zero carbon standard (see Chapter 1) and came into effect in 2006 (DCLG, 2006). It was intended to provide ‘a single national standard to guide industry in the design and construction of sustainable homes [and to] driv[e] continuous improvement, greater innovation and exemplary achievement in sustainable home building’ (ibid.:4). As well as being intended to bring about a step-change in sustainable home building practice, the CSH was seen as a tool that would enable developers to differentiate themselves in a competitive market, and a way to assist home-buyers in their choice of home (ibid.). To this end, the Code was intended to complement the system of Energy Performance Certificates (EPCs) subsequently introduced in 2007 under the European Union’s Energy Performance of Buildings Directive (EPBD) (Gibbs and O’Neill, 2015).

According to the CSH, progressive improvements in the sustainability performance of new-build housing developments would be demanded by interim step changes, in order to enable the zero carbon housing 2016 target to be met. Initially introduced as a voluntary framework, in 2010 level three (a 25% energy performance improvement relative to 2005 Building Regulations) was made mandatory for all new build homes (Planning Portal, 2010), and it was originally planned that in 2013 level four would be made mandatory for all new housing (DCLG, 2007b). Some commentators suggested that the UK house building industry would be completely unprepared for the challenges posed by this introduction of increasingly stringent sustainability standards, and were concerned that the sector did not have the technology, knowledge or institutional structures required to deliver this transformation in practice (Lowe and Oreszczyn, 2008). To overcome these perceived ‘barriers’ to change, the Government also developed an institutional framework to support changing practice by forming the ‘Zero Carbon Hub’ (ZCH) - a public-private partnership to guide the zero carbon programme - and the Technology Strategy Board’s (TSB) Low Impact Buildings Innovation Platform (Gibbs and O’Neill, 2015).

The CSH was to differ to Part L of the Building Regulations, in that it would address wide-ranging aspects of sustainability performance as opposed to concentrating on the conservation of fuel and power alone. The Code would use a rating system to assess nine ‘code design’ categories – energy/carbon emissions, pollution, water, health and well-being, materials, management, surface water run-off, ecology and waste. A system from one to six stars based on performance against these design categories would communicate the overall sustainability performance of a new-build house - where one would be the lowest (or ‘entry level’) and six the highest standard, reflecting exemplary development. According to the original definition of this standard, a level six home would be deemed a zero carbon home, defined as having ‘zero net emissions of carbon dioxide from all energy use in the home including heating, lighting, hot water and all other energy use’ (Panagiotidou and Fuller, 2013: 197). In an attempt to encourage innovation and cost-effectiveness, while based on performance, the Code was not prescriptive in how these levels should be attained (Gibbs and O’Neill, 2015).

‘At first sight, the development of more and better energy-efficiency standards [to improve housing construction and building energy performance] is an unquestionably

‘good thing’’ (Shove and Moezzi, 2002: 265) and it would seem sensible to argue for their widest possible adoption. Shove and Moezzi point out, however, that the uptake of standards involves a ‘diffusion of the cultural and historically specific assumptions and conventions in them’ and warn that they can ‘inadvertently legitimis[e]

unsustainable habits, practices and conventions’ (ibid.: 276,7). The CSH, whilst seeking to modify certain areas of daily life, carries and reproduces many assumptions about normal everyday life, and fails to question the extent to which these assumptions perpetuate established ways of doing (Spurling et al., 2013). For example, when considering house size, the Code makes special provision for calculating energy loss in bungalows – indicating that this potentially less thermally-efficient type of house building should be accommodated. Should then building energy performance and sustainability be viewed as a ‘single state of affairs’ (as with universal standards) or as ‘a matter of degree, and of contest and negotiation’ (ibid.: 46)?

It was intended that the Government’s approved methodology for assessing the energy rating of dwellings, the Standard Assessment Procedure (BRE, 2009; 2012), would underpin the CSH accreditation process. This calculative method would appraise the typical annual energy costs and carbon emissions per house for heating, hot water,

ventilation and internal lighting, including provision for energy savings from micro-energy generation (McManus et al., 2010). This assessment procedure, which also underpins the Building Regulations, is measured on a scale from 1 to 100+, where 100 means that the house is zero carbon and dwellings that have a SAP greater than 100 are net exporters of energy. The calculation, takes into account a range of technical factors that contribute to energy-efficiency, for instance, thermal insulation of the building fabric, efficiency of the heating system(s) and solar gains (BRE, 2009; 2012).

This quantitative SAP methodology has distinct limitations however, as it does not take into account: household size and composition, ownership and efficiency of particular domestic electrical appliances, or heating patterns and temperatures. Furthermore, this methodology overlooks how the everyday lives of household residents determine how a house is lived-in, and influence a home’s overall energy balance.

From the outset, a particular area of contention with the CSH standard was the precise definition of zero carbon. Whilst the original definition stated that ‘net carbon dioxide emissions from all energy used in the dwelling are zero or better’ over the course of a year (DCLG, 2006; 2007a), the practical implementation of CSH level six was far from clear and led to contestation by builders, architects and policy organisations alike (McLeod et al., 2012). According to some definitions, zero carbon could be met by including on-site micro-generation of electricity at the level of a development rather than an individual dwelling. In addition, offsetting - compensating for emissions from a dwelling by low carbon power generation off-site - was left to be decided at a later date (Gibbs and O’Neill, 2015). Furthermore, although discussed during the consultation process for the new regulatory framework, embodied carbon⁶ was excluded from the first definition (DCLG, 2007a; McManus et al., 2010; Monahan, 2013).

Given the conservative nature of the housing industry, it was perhaps unsurprising that there were immediate objections to the ambitious scope of the carbon zero housing target. A UK Green Building Council (UKGBC) Task Group report warned that

‘…anywhere from 10% to 80% of new homes may not be able to meet the current definition of zero carbon’ through on-site measures alone (UKGBC, 2008: 5), and the majority of large housing developers expressed concerns regarding the ‘cost of building to this definition… and its impracticality on many sites’ (ZCH, 2013: 4). In response, the Government launched a consultation on the workability of the zero carbon

⁶ Embodied carbon: Carbon dioxide emitted during the manufacture, transport and construction of building materials,

definition (ZCH, 2009). The definition of zero carbon housing was revised in the 2011 Budget, in line with the SAP, to exclude operational emissions attributed to ‘plug-in’ appliances, such as televisions and computers, and to only target energy use from heating, hot water, fixed lighting and building services (ZCH, 2011).

This revision effectively led to CSH level six standardising carbon zero houses rather than homes as the definition no longer considered the operational energy and carbon consequences of lived-in properties. It also transferred the task of providing clean energy for new homes from the house-builder to the wider power sector.

The new definition was particularly problematic, as energy-dependent appliances are expected to increasingly constitute a greater proportion of domestic energy consumption, as heat loss standards improve and electrical ‘gadget’ ownership continues to rise and devices demand higher energy inputs (EST, 2012; DCLG, 2007a). For some, this revision therefore represented a serious dilution of the zero carbon standard. For example, it led to the World Wildlife Fund’s resignation from the zero carbon task-force (WWF, 2011).

The DCLG consultation also set out a tiered approach to delivery of Zero Carbon homes. This proposal shifted the zero carbon standard from the individual house to the housing development and allowed for carbon emissions abatement off-site.

The proposed hierarchical approach to defining zero carbon homes (Figure 3.1) was founded on high minimum standards of fabric energy-efficiency and the use of efficient heating, cooling, ventilation and lighting systems DCLG (2008a; ZCH, 2012).

Renewable technologies and directly connected district heating solutions situated on the site of the building itself formed the second tier and also had a minimum carbon compliance standard. Beyond this, emission reductions could be achieved through a range of cost capped off-site Allowable Solutions. Examples of such measures would include use of, or investment in; large-scale renewable energy technologies, district heating projects, low carbon street lighting, or contributions to the Green Deal (DECC, 2015d). ‘By paying into an Allowable Solutions fund (to pump-prime carbon-savings projects elsewhere), a lower on-site emissions target could be set for house-builders while preserving the zero carbon policy goal’ (ZCH, 2013: 4). This provided developers with an economic way of compensating for hard to achieve on-site carbon emission reductions, but crucially also ‘effectively introduced a buyout clause’ for the

ORIGINAL IN COLOUR

Figure 3.1 – Hierarchical approach to defining zero carbon homes

(Source: ZCH, 2012: 6)

Reducing residential energy demand and carbon emissions from new housing has long been defined as a technological problem. In seeking to phase-in higher standards of low-energy housing design and construction the CSH building performance standard set ambitious transformative goals for the residential sector. Its ambitious targets and broad understanding of sustainability make the CSH an interesting case of housing performance enhancement. However, this section has shown that the standard was underpinned by a quantitative calculative assessment that failed to consider the house as a lived-in home, and the ambitions of CSH were diluted following housing industry lobbying. It has also raised concerns regarding the role of building performance

standards in the housing industry, which whilst seeking to transform industry practice, can also unwittingly lock-in an accepted reliance on energy-related services, and increase the overall energy balance of the residential sector.