A Zero Carbon Hub – led Task Group concludes that much work needs to be done to ensure good performance of Mechanical Ventilation with Heat Recovery (MVHR) systems in people’s homes.
Reinforcing findings of the Interim Report published in January 2012 and drawing on available evidence, the Ventilation and Indoor Air Quality (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 Regulation requirements.
Over the past few years, the trend towards higher levels of energy efficiency of new homes has led to improved building fabric airtightness and to the increased use of mechanical ventilation with heat recovery (MVHR). In 2012 in the UK, 24,000 MVHR fan units were installed and it seems that this increasing trend is one that will continue.
Despite the number of MVHR units installed, only a limited sample of those incorporated into recently built homes have been monitored. The vast majority of the available evidence, whether from the UK or abroad, points to issues across the piece that need to be addressed – issues with design, installation, commissioning, operation and use, all of which affect system performance and could compromise air quality.
A lack of good practice across industry in dealing with ventilation systems serves to highlight competence as a key issue. Regrettably existing training schemes have made limited progress and Task Group members are calling on DCLG to consider mandatory competency requirements for MVHR installations so that standards can be driven up.
However, examples are beginning to emerge which demonstrate that when done correctly, MVHR systems do deliver good performance. A good example and one from which some useful lessons can be drawn is the development of 14 houses built in Wimbish, Essex, to the Passivhaus standard, where increased attention to detail has paid off.
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 allergic and asthma symptoms. Regardless of the type of ventilation systems chosen, the Task 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.
Author of the report, Neil Smith, Head of Innovation and Research at NHBC commented:
“As we move towards zero carbon standards, the single issue that causes us greatest concern is indoor air quality in new homes. Work carried out by the NHBC Foundation in 2009 demonstrated a link between poor indoor air quality and health concerns and highlighted specific concerns in relation to design and installation standards for MVHR.
“After almost 4 years’ consideration of the issues and reviewing feedback from the 2009 research and multiple other studies, the VIAQ Task Group considers that there are serious issues to address to ensure that homes provide a comfortable and safe internal environment for occupants.
“With MVHR already being installed in around one quarter of new homes, and set to grow, it is clearly essential that the concerns identified are dealt with as a matter of priority. As part of this process, NHBC is completing the development of a new NHBC Standards chapter giving good practice guidance on MVHR, which will be published towards the end of the year. We hope that this, alongside the concerted action between industry and government as called for by this Task Group, will significantly improve design and site practice.”
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Notes for Editors:
The Task Group’s Final Report can be downloaded from the link ‘Mechanical Ventilation with Heat Recovery in New Homes’
Zero Carbon Hub - The Zero Carbon Hub was established in response to the Callcutt Review recommendation, to make zero carbon homes a reality from 2016. It is a public and private partnership responsible for galvanising action and working with Government, councils and industry to overcome barriers to ensure this ambitious policy is implemented.