Indoor air quality
time for change N
Air quality:
Roy Jones, technical director Gilberts Blackpool unpicks the tricky problem the building services sector is facing in balancing the drive towards carbon zero with delivering appropriate, healthy internal environments
ew targets for operational energy performance and embodied carbon (i.e. whole life carbon standards) have already
been proposed for new builds (RIBA 2030 Climate Challenge), with retrofit to follow sometime this year.
The emphasis on cutting emissions, optimising
energy efficiency and building airtight also puts pressure on us to ensure there is still good indoor air quality (IAQ). Ventilation is essential for any occupied building,
so it, and the occupants, can breathe. The average person generates at least 40g of water vapour an hour, depending on activity: that’s a lot of moisture accumulating indoors. Moist air within must be exhausted to avoid damp, condensation and mould. Build tight but ventilate right.
IAQ targets
RIBA 2020 Climate Challenge action advises that new build IAQ targets are CO2 levels <900ppm, total VOCs of <0.3mg/m3
domestic office buildings of <750kgCO2e/m2
and embodied carbon for non- . The
RIBA guidance also acknowledges that the priority should be placed on refurbishment and retrofitting of existing buildings. Our industry body, CIBSE, is already working closely with RIBA to develop an implementation plan. This has already been updated following COP26. The RIBA guidance inevitably references Building
Regulations, in particular for the above, Approved Document F (ventilation), updated draft for 2021 with emphasis on uprated performance, reduction in ductwork to reduce risk of pollutant build-up and improved commissioning.
Regulatory changes
Approved Document F (draft at consultation stage) is recommending a minimum ventilation standard of 15 litres per person in certain specific occupied rooms with a high level of air consumption and/ or where large groups accumulate. It also advises
12 February 2022
www.heatingandventilating.net
a means of monitoring CO2 within the occupied space (unless a very small room or atrium). The Document currently states that “office buildings should have the ability to provide adequate outdoor air to all occupied spaces without recirculating air within spaces or between different spaces, rooms or zones, unless the ventilation system has an ultraviolet filter, HEPA filter or other germicidal filter”. It still recommends 10 litres per person in office areas, with the added caveat of needing to achieve that whilst also delivering at least one litre per second per metre square of floor area. The Document further proposes purging of air before a building is occupied. Just to further complicate things, the Department
for Education’s Facilities Output Specification, affecting building services in schools, has also been
updated. It now encourages low carbon solutions for warming, ventilating and cooling the building, preferably via the use of natural ventilation as the preferred strategy; use of heat pumps is noted over other alternative strategies and services. Also, the NHS has updated its industry-specific
guidance, Health Technical Manual HTM 03-01, which similarly affects ventilation and IAQ. The HTM guidance requires the default ventilation of healthcare buildings to be natural, with mechanical systems as a last resort. Supply ventilation is also to be filtered where relevant e.g. operating theatres. As an aside, the hospital environment emphasises why improving the IAQ is so important: 10% of patients contract an infection whilst in hospital, and up to 25% of infections as a result of surgical interventions come from an airborne route.
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