Its Clean Air Day today (17th June 2021) and the Worlds’ focus is on the quality of air that we breathe. Unsurprisingly a lot of attention is being given to outdoor air pollution, with people being asked to reduce emissions by walking, cycling or using electric vehicles. However, less attention is being given to the quality of indoor air in buildings, yet this potentially has a far greater effect on the health of the nation.
Indoor Air Quality (IAQ) is a critical issue given that people living in developed countries can spend as much as 90% of their time indoors. This has been exacerbated by the measures put in place to combat Covid with the most susceptible individuals – such as the elderly and those with pre-existing medical conditions – spending almost all their time inside. Greater provision of Houses in Multiple Occupation (HMO’s) have also seen an increase in this issue with people living in cramped single aspect rooms, and undertaking cooking, living and sleeping functions all within the same multifunction space.
When the energy efficiency standards in Part L of the Building Regulations were strengthened in 2006, 2010 and again in 2013, new buildings were required to be more airtight by reducing heat losses through unwanted gaps and cracks in the fabric. However, by reducing this uncontrolled ‘infiltration’ it means that far more care must be taken with the ‘purpose-provided ventilation’ from devices such as trickle ventilators and fans designed into the building. These are controlled under Part F of the Building Regulations with guidance being contained in Approved Document F (ADF).
There is still clearly a lack of understanding of the health risks associated with IAQ, and its rare that a week goes by where we are not asked by an Architect if they can omit trickle vents because they are not aesthetically pleasing, or a contractor asking if a workplace can omit mechanical ventilation as the client doesn’t want to pay for it.
In 2019 the Ministry for Housing Communities and Local Government (MHCLG) published a study into the quality of air in mew homes. In total, 80 homes had been studied in the period from November 2015 to February 2016, across seven developments within England, and the results were shocking as nearly all homes did not meet the recommended ventilation provisions – some by very significant levels.
Only 2 of the 55 naturally ventilated homes met the guidance in ADF with respect both to trickle ventilator provision and local extract fan air flow rates. Homes with whole house mechanical ventilation systems faired no better with just one of the 25 homes in the study meeting the guidance published in ADF with the cause being that the extract fan flow rates were below those recommended, in some cases by as much as 85% below the recommended flow rate.
These results are especially disappointing given that one of the key changes in the Part F 2010 revision was the introduction of a legal requirement for testing and commissioning of installed fans, and for the installer to notify the building control body of the commissioning and the air flow rates. This is again an area where we see huge resistance from contractors to supply the necessary certification prior to occupation.
There is also currently a lack of awareness amongst the occupiers of buildings, of the vital role that ventilation plays and how and when to operate that ventilation. Nor are people aware that certain activities such as cooking or even using scented candles are polluting the indoor environment. It is likely that if occupants were more aware of this, they would try to keep such activities to a minimum or ensure that appropriate measures (such as purge ventilation) are used as mitigation.
In 2006 ADF sought to introduce a complementary strategy of ‘source control’ by reducing the release of volatile pollutants into the indoor air. Sources include formaldehyde and VOCs from plastic-based building components, fabrics and furnishings. In 2012 the Zero Carbon Hub recommended that such products or components be banned from use indoors and recommended the greater use of natural products with low or zero emission of pollutants.
The Government have responded to these finding and in January of this year published a consultation on revisions to ADF. This included a recognition that Mechanical ventilation has the potential to be the most proficient means of ventilating a modern property, although this provides a conflict with the need to reduce carbon emissions and energy use. The revised guidance proposes an increase the minimum airflow through these systems to each bedroom by 6 l/s. This has been introduced as there are concerns especially in bedrooms overnight when doors are kept shut – this is especially true in HMO type accommodation. The other expected change here is an increase in the background ventilation from 2500 mm2 to 5000 mm2 in extract-only systems.
Its not just new building’s either that need to be addressed, as the overall drive to improve thermal efficiency and the increased demand for home extensions are also having a negative effect on IAQ. For example, simply replacing existing windows is likely to increase the airtightness of the building. If ventilation is not provided via a mechanical extract and supply ventilation system, then increasing the airtightness of the building will reduce useful ventilation in the building. In these circumstances, it should be ensured that the ventilation provision is considered, and additional measures introduced to prevent IAQ reaching unacceptable levels.