UCL Institute for Environmental Design and Engineering


Air PermeAbility: Cities Health Energy (APACHE)


6 February 2017

Key facts

  • Funding Body/Client  UCL Grand Challenge of Sustainable Cities
  • Project Partners: UCL Energy Institute
  • Total Project Value: £2,950 
  • UCL/IEDE Project Value Share: £2,950
  • Duration: 2012-2013
  • Status: Complete

The APACHE project initiated new research cooperation to support the development of multidisciplinary techniques to critically review air permeability in dwellings in the UK and collate the existing evidence on the building fabric permeability levels into a comprehensive database that facilitates in depth analysis.

Building air permeability is the uncontrolled leakage of outside air into the building space. This can occur at numerous points: through cracks, gaps around doors and windows, as well as through the roof, floor and gaps around pipes and ducts. Air can also leak through porous construction materials such as bricks or blocks.

Air leakage through the building envelope contributes to ventilation, heating and cooling costs and has an impact on moisture migration and indoor air quality. Air change currently accounts for approximately 35% of total space conditioning energy use in buildings in the domestic and non-domestic building stock in the UK.

Leakier buildings are, thus, characterised by higher space heating needs and, as a consequence, higher CO2 emissions. Due to the current plans for decarbonisation of the national energy grid, the energy infrastructure will soon experience major changes. However, more than 60% of the approximately 26 million existing dwellings will still be standing in 2050. It is, thus, necessary to effectively adopt strategies to improve the energy efficiency of the existing housing stock.


PI: Anna Mavrogianni

Co-I: Catalina Spataru

R: Chrysoula Thoua 


The main outcomes of the APACHE project are:

  • an academic journal paper reviewing the existing evidence on the fabric air leakage distribution across the UK housing stock,
  • an academic journal paper exploring the implications of existing evidence on the air leakage of UK dwellings for policy and building regulations,
  • a database of air leakage measurements of UK homes collated from existing studies,
  • an one-day workshop that brought together building construction industry and policy stakeholders to discuss the outcome of the study and its implications for policy, research and industry practices,
  • a video of the workshop presentations and discussion (soon to be made available via Bartlett TV).

The indirect outcomes were:

  • to establish interdisciplinary collaboration between two departments within UCL (IEDE and UCL Energy Institute), and
  • to bring together different experts and establish collaboration through the workshop with experts and stakeholders from different areas (academics, government representatives, consultancy companies). 

Very little is known to date about the distribution of air leakage of existing dwellings in the UK and no comprehensive database of air leakage values by dwelling construction age and typology exists. The APACHE project enhances our understanding of the magnitude of air leakage in the existing housing stock and offers suggestions for future data collection studies and legislative actions. The outcomes of the study are valuable for building designers and policy makers as it will allow them to take air permeability into account when designing energy efficient retrofit interventions and will facilitate further research in both the public and private sector. 


For further information please contact: Anna Mavrogianni