UK policy on ‘Zero Carbon’ homes
The implications of anthropogenic climate change as outlined in the IPCC AR5 , have resulted in a major global policy shift towards climate change mitigation. In response, the UK government has pledged to reduce emissions of greenhouse gases to 80% of their 1990 baseline by 2050 Currently 36% of UK CO2 emissions arise from buildings, with the residential sector alone accounting for 23%. The UK construction industry is also responsible for the consumption of 420Mt of materials, 8Mt of crude oil and the emission of 29MtCO2 annually (Hammond and Jones, 2008. Further it is anticipated that 3 million new homes will be constructed by between 2007-2020; with the vast majority being additional to the existing stock. However the Committee on Climate Change estimate there is scope to reduce emissions from the sector by 74% by 2030.
Various initiatives such as the Warm Front scheme, Carbon Emissions Reduction Target (CERT) and most recently Energy Companies Obligation (ECO) and the Green Deal have sought to improve the energy efficiency of the existing housing stock. There have also been major steps to reduce the energy and CO2 emissions of new buildings. This has been primarily done through Part L1A of the building regulations – Conservation of Fuel and Power in New Dwellings. Recent announcements by the UK government however have placed significant uncertainty on the future commitment of the government; to both low and zero carbon housing and retrofit through the defunct Green Deal.
The primary metric in Part L1A is the target emission rate (TER), this accounts for CO2 emitted in heating, fixed cooling, hot water and lighting and is expressed in KgCO2/m2/year. Dwellings are assessed using the standard assessment procedure (SAP) and achieve a dwelling emission rate (DER), that must be equal to or lower than the TER in order to comply with building regulations. The regulations include minimum standards for the thermal performance or u-values (W/m2K) of building components such as walls and windows and air permeability m³/ (h.m²). The standards are being progressively tightened through successive revisions of Part L1A, as indicated by.