The Association for Environment Conscious Building (AECB) is the leading^{[citation needed]} network for sustainable building professionals in the United Kingdom. Membership of the AECB includes local authorities, housing associations, builders, architects, designers, consultants and manufacturers. The association was founded in 1989 to increase awareness within the construction industry of the need to respect, protect, preserve and enhance the environment and to develop, share and promote best practice in environmentally sustainable building.

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While the AECB recognises that all aspects of sustainability are important, it believes that climate change threatens to overwhelm its members' achievements in other areas. It is therefore currently focusing on trying to help reduce carbon emissions related to domestic and non-domestic buildings in the UK (around 50% of UK CO₂ emissions – excluding flying – relate to buildings). The association believes that the Government's target of a 60% reduction in CO₂ emissions by 2050 is too little, too late, and that a reduction of at least 85% is required to meet the challenges of climate change.

A guiding principle of the AECB is to focus on what really works in practice, to deliver buildings with genuinely improved environmental performance. The AECB established the Low Energy Buildings Database with the support of the Technology Strategy Board^[1] to show people what could actually be achieved in reality, as opposed to what people hoped they might achieve when developing the design. The database draws on the collective experience of AECB members, and now also the team’s involved in the Retrofit for the Future projects,^[2] and shares that learning. Almost uniquely, this database gives an honest account to anyone planning a low energy building of what can be achieved, along with a detailed account of how it has been done.

The database includes information on both refurbishment and new build projects, in both the domestic and non-domestic sectors. The database shows the performance of each building, in both figures and clearly presented graphs. Design intention can easily be compared with built reality, and projects can easily be compared with each other. For each project you can see detailed design strategies, descriptions and illustrations of the building type, the measures taken and technologies employed. As the monitoring figures accumulate, the database will offer increasing numbers of well-illustrated and robust benchmarks for the energy and carbon performance levels that can be achieved, across a wide range of building types.

On 30 January 2012 the AECB released its report Less is More: Energy Security after Oil^[3] which was published at the end of an unprecedented fifteen years in UK energy policy history. It began with the formal acceptance of the need for a climate change policy by the last Conservative Government in 1997^{[citation needed]} and culminated with the Climate Change Act 2008 and the 4th Carbon Budget.^[4] Less is More is a significant new contribution to the debate and offers an alternative to the emerging orthodoxy of large-scale electrification of heat and road transport as a way to achieve or beat the UK's 2050 CO₂ emissions target. This is based on more vigorous and systematic pursuit of energy efficiency throughout the economy; on technologies such as large-scale solar heat, piped to urban buildings; a road and air transport system synthesising liquid fuels in part from renewable electricity, supplementing the biofuel resource; a small electricity supply system, supplied largely by despatchable sources, assisting with network security; and the more vigorous pursuit of carbon dioxide (CO₂) sequestration options, particularly in the biosphere.

Less is More contends that an electric future is more costly and could be slower to deliver significant CO₂ reductions than the alternatives. Vigorous pursuit of energy efficiency, plus biosequestration, plus more focus on UK energy uses and the characteristics of energy systems, sets the stage for significantly cheaper and more secure energy supply options. Less-electric futures appear to have the capacity to deliver CO₂ reductions both more cheaply and more quickly than more-electric. Cumulative emissions to 2050 are at least as important as emissions in the year 2050. The report highlights key areas for technology, product and supply chain development. They include piped heat, which is a mature technology in several of Britain's continental neighbours, and heats over 60% of Danish buildings, but remains uncommon in the UK. They include high-performance insulation systems that could significantly reduce losses in heat storage and distribution systems at all scales, along with renewable fuel production. Heat networks play a systematic role in the scenario, opening up access to large-scale solar, geothermal and waste heat resources at lower costs than new electricity sources and reducing the risk that the UK will be unable to keep the lights on.

Less is More contains a critique of the dysfunctionality of UK energy markets. The authors note that water is supplied by vertically-integrated and regulated local monopolies, which have access to capital at near-public sector interest rates, especially if they are debt-funded. They pose the question of why such arrangements cannot be used again in the energy sector, paralleling as it happens the situation with some private US utilities and with utilities in Denmark. The report does not offer the prospect of an easy path to energy independence and decarbonisation. It makes it very clear that all options pose acute difficulties. But it warns policy-makers not to reject technologies just because they appear difficult without making sober comparisons with the reality of the other technologies under consideration.^[5]

The AECB followed up Less is More with the Post-Fossil Fuel Building Construction and Materials report and continues to publish original material, training courses and podcasts. In 2022, it launched its own free magazine "Setting the Standard" which contains original commentary, analysis and thought pieces from the world of sustainable, green building.