A recent report from the Ventilation and Indoor Air Quality Task Group, led by the Zero Carbon Hub, concludes that much work needs to be done to ensure good performance of mechanical ventilation with heat recovery systems in new homes.
Reinforcing findings of its interim report published in January 2012, the VIAQ Task Group recommends that concerted government-led action should be taken to develop and promote good practice and to ensure public health and safety, with new research informing future Building Regulations.
Increased use of MVHR with little monitoring
Over the past few years, the trend towards higher levels of energy-efficiency in new homes has led to improved building fabric airtightness and to the increased use of MVHR. In 2012, 24,000 MVHR fan units were installed in the UK, a trend that is set to continue.
Despite the number of MVHR units installed, very few have been monitored in use.
“As energy-efficiency and airtightness of new homes improves, the single issue that causes greatest concern is indoor air quality”
Most of the available evidence from the UK and other countries points to issues that need to be addressed as a matter of priority – design, installation, commissioning, operation and use, all of which affect system performance and could compromise air quality.
Based on the evidence reviewed by the VIAQ Task Group, there is little doubt that poor indoor air quality is connected with a wide range of undesirable health effects, including allergies and asthma.
What needs to be done
The group’s findings reinforce the need for the design, construction and commissioning of buildings to be undertaken with internal air quality and the provision of adequate ventilation firmly in mind.
As energy-efficiency and airtightness of new homes improves, the single issue that causes greatest concern is indoor air quality.
With MVHR already being installed in around one-quarter of new homes, it is clearly essential that the concerns identified are dealt with urgently.
As part of this process, we are completing the development of a new National House-building Council standards chapter giving good practice guidance on MVHR, which will be published towards the end of the year.
But further concerted action between industry and government, as called for by this Task Group, is also essential.
Neil Smith is head of innovation and research at the National House-building Council