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INTRODUCTION

The aim of the work underlying this report is to explore the extent to which improving the energy efficiency of the existing UK building stock would be a more costeffective route for achieving CO₂ savings than constructing new buildings to the higher levels of energy performance required to meet LZC targets for new build. The work is based on existing data and analysis, much of which has been carried out by BRE, and seeks to determine where the best balance lies between high energy performance standards for new build and refurbishment of the existing building stock.

While moving towards zero carbon for all new buildings can undoubtedly achieve a significant reduction in CO₂ emissions in the future, existing buildings are expected to form the majority of the UK's building stock for many years to come since around three-quarters of houses and 60% of non-domestic buildings in 2050 are likely to have been built before 2010. Most existing buildings in the UK were constructed before building regulations were extended to consider energy, and while many will have undergone some energy efficiency improvements (eg installation of double glazing, replacement of inefficient boilers), significant potential for further energy efficiency savings remains. Recent estimates indicate that the technical potential for reducing CO₂ emissions in the UK building stock is around 40%, and of this around 20% can be saved cost-effectively.

In order to assess the size of savings available and the cost-effectiveness of those savings for both refurbishing existing buildings and constructing new buildings to LZC standards, this project looks at:

• the potential future building stock broken down by age of construction
• the energy efficiency improvements that could be made to the existing building stock
• the energy efficiency improvements required to achieve LZC standards in new buildings
• the investment costs and the CO₂ and cost savings associated with refurbishing existing buildings and constructing new buildings to LZC standards‡

This project makes use of existing data generated for other projects for Defra and the Committee on Climate Change. Domestic and non-domestic buildings have been assessed separately due to the very different nature of both the buildings involved and the data available.

‡ Although we use the term ‘savings' for both existing and new buildings, the savings in the latter should more accurately be referred to as ‘avoided future emissions' since these buildings do not yet exist.