Air Quality in New Homes

Air Quality in New Homes

We carried out a two-year study with the Mackintosh Environmental Architectural Research Unit (MEARU) of 20 newly built homes across London, investigating how they performed compared with predicted performance during the design stage.

Our research focused on health and wellbeing rather than energy efficiency, its long-term aim being to identify gaps in performance and devise practical solutions to close them.

The 20 properties studied by Cartwright Pickard and MEARU were representative of the housing stock built by London’s biggest contractors for well-known housing associations, the major producers of housing in their boroughs.

The houses were designed and built to Code for Sustainable Homes levels 3 and 4, Eco homes ‘very good’ rating and in accordance with the Building Regulations.

The dwellings incorporated energy-efficient strategies such as high levels of thermal insulation, airtight buildings with whole-house ventilation systems and high energy performing windows. However the research findings revealed significant gaps between the designed and actual dwelling performance, both in terms of energy use and environmental performance.

The indoor air quality within the 20 dwellings was a particular cause for concern. The ventilation provision adopted at the dwellings’ design stage was not performing adequately, with problems identified relating to design, construction quality, installation and commissioning, occupant interaction and maintenance.

Internal carbon dioxide (CO2) levels are used as an indicator of air quality – while CO2 concentrations would need to reach extreme levels to be directly harmful to humans (4,000ppm-plus), levels above 1,000pm (parts per million) are seen as an indicator of poor ventilation.

This can have consequences through the accumulation of pollutants such as VOCs given off by modern building materials and furniture etc., as well as increased moisture levels leading to dust-mite proliferation and mould growth, which can lead to asthma.


In 2008, the UK government made a commitment that by 2050 it would have reduced carbon emissions by 80%. Since then regulatory attention has focused on improving energy and carbon performance, for example through increased insulation and airtightness, and more efficient heating.

This has set the industry on a path to unintended health consequences, with problems caused by, for example, inadequate ventilation, evaporation of volatile chemicals into the air, and reduced standards of space and light. The resulting health risks are both physiological (respiratory disease, diminished immune system, diabetes, obesity) and psychological (seasonal affective disorder, depression).

Europeans spend 85-90 per cent of their time indoors, whether at home, work, school or leisure. Over the years there have been major changes to building design and materials, to the furniture, finishes and equipment we put into them and to the ways in which we use them. At the outset of the 20th century approximately 50 materials were used to construct buildings.

By the end of the century this list had grown to around 55,000, half of them synthetic. Compounds implicated in indoor air quality toxicity are emitted from the building materials, furnishings and fittings, cleaning products, and somewhat ironically even air fresheners. One result has been to amplify the effects of indoor environments on our health.

Key findings

  • CO2 concentrations rose above the recommended threshold level of 1,000ppm in 95 per cent of the properties we monitored
  • Indoor CO2 levels were worst in winter, with concentrations rising above the recommended level of 1,000ppm for 54 per cent of the occupied hours
  • In some properties we found CO2 levels over 2,000ppm for sustained periods of time, with peaks of 3,250ppm not uncommon
  • Ventilation systems were often badly installed and incorrectly commissioned. This was particularly prevalent in dwellings with Mechanical Ventilation with Heat Recovery (MVHR) systems, which need to be carefully installed and commissioned to gain maximum operating efficiency
  • Ventilation units were also poorly maintained. Most commonly we found the air filters had not been changed or cleaned, reducing the airflow through the system and restricting the ability to extract stale air and supply fresh air
  • The majority of the MVHR systems tested failed to meet the Building Regulations’ advisory airflow rates
  • Trickle vents above windows were either non-existent, closed or covered by curtains or blinds, reducing the flow of fresh air into the properties
  • Most of the properties overheated during the summer months, in part because of excessive solar gain from unprotected full-height windows, but exacerbated by underperforming ventilation systems failing to extract sufficient stale, warmed air to keep spaces ventilated. The summer bypass function required by MVHR systems to reduce overheating was often not working or incorrectly set up
  • We also identified a series of design and build quality issues causing low internal temperatures in the dwellings and affecting occupant comfort

Read the full report here

Air Quality in New Homes