AIR CONDITIONING, COOLING & VENTILATION Redressing the balance of ventilation
The new Approved Document Part F of the Building Regulations, published in December 2021, is being hailed as a “vital step to improve indoor air quality” on the road to Net Zero. With the introduction of the 2021 edition, the focus has been clearly defined as health and energy efficiency, which is a positive move following the COVID-19 pandemic. David Cook, technical product manager at Vent-Axia, explains more on what this means for consultants working on commercial buildings
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ince Kyoto, the UK has been striving to reduce its carbon emissions. However, unfortunately indoor air quality (IAQ) has taken a back seat. This has resulted in indoor air pollution. The new
revision of Part F has started to redress the balance of ventilation with energy efficiency since the pandemic has clearly shown the importance of good IAQ to health and wellbeing As buildings become more airtight to improve efficiency it is essential to consider IAQ too to protect the wellbeing of inhabitants. The new Part F (Means of Ventilation), which goes hand-in-hand with the new amended Part L (Conservation of Fuel and Power), therefore sets out “significant changes”, which will drive adoption of low carbon ventilation as an industry standard and improve the quality of the air we breathe in buildings. This includes the new Part F looking to both minimise the entry of external pollutants and ensure humidity and pollutants are extracted effectively and efficiently both in new build and refurbishments. The document also includes guidance on minimum levels of air quality, to ensure good occupant health, and considers ways to monitor IAQ as part of this.
Approved Document F, Volume 2
So, what are some of the significant areas to consider in the new revised Part F for consultants working on non-residential buildings? (Interestingly for the first-time flats with communal areas now also come under Approved Document F, Volume 2: Buildings other than dwellings.) With Part F focusing heavily on health and wellbeing it is no surprise that a key addition to the document is a new section on monitoring IAQ. During the pandemic indoor air monitoring through CO2 monitors has already had a heavy focus in schools to try to reduce virus transmission. Since people exhale carbon dioxide (CO2) when they breathe out, if there is a build-up of CO2 in an area, IAQ falls and it can indicate that ventilation needs to be improved.
Monitoring IAQ
Part F therefore sets out a requirement for new commercial buildings to have the means of monitoring indoor air quality in occupiable rooms. These include (but are not limited to): occupiable rooms in offices; gyms; indoor sports venues; theatres; night clubs; pubs; hotels; and other rooms where people are likely to gather indoors. This does not apply to small spaces up to 125m3 volume, or 50m2 floor area. It also does not apply to large spaces over 800m3 in volume, or 320m2 floor area.
This may be achieved using CO2 monitors or other means of measuring IAQ. Where CO2 monitors are used, for best accuracy they should be mains powered NDIR type, mounted at least 500mm away from people and at breathing height, and away from windows, doors and ventilation. Guidance on how to use CO2 monitors is set out in Appendix C of Part F. Vent-Axia has a range of CO2 sensors which can be discreetly located on a wall and can intelligently boost ventilation based on the detected CO2 levels. They can also provide a warning indication for occupants if CO2 levels rise above acceptable levels with a useful traffic light system on the front, so occupants can activate purge ventilation when required.
CO2 should only be used as a guide to ventilation rather than to identify safe thresholds. CO2 measured in parts per million (PPM) with external levels around
400PPM. A well-ventilated space would have average levels of around 800PPM, whereas average levels of 1500PPM would indicate that the space is poorly ventilated and action should be taken to improve the situation.
Minimising ingress of external pollutants
Another key point within the revised Part F, is that ventilation systems should be designed to minimise external pollutants entering the indoor space. Part F now clearly states that this should be taken into account if certain pollutants, including carbon monoxide, sulphur dioxide, lead and PM25, exceed limits as outlined in the Air Quality Standards Regulations 2010. This is also the case if a building is located to near to sources of significant external pollution such as busy road / junctions, combustion plants, discharges from process plants, and other sources of pollution that may be detrimental to health. To combat the ingress of external pollutants in general, locate intakes away from the source of the pollution; where urban traffic is the cause of the pollution air intakes should
12 BUILDING SERVICES & ENVIRONMENTAL ENGINEER APRIL 2022
be as high as possible and located on the less polluted side of the building; if practical, avoid intakes from courtyard / enclosed areas; and if there is a significant prevailing wind direction, intakes should point in the opposite direction to the exhaust. Approved Document F, Volume 2 advises that mechanical ventilation may be the most practical way of achieving this. For example, Vent-Axia’s Slimpak EC box fan ducted system continuously supplies fresh air or extracts stale air or both. These fans can be connected to a CO2 sensor for optimal air quality control.
Energy efficiency
Another key addition to Part F, which reflects the significance of ventilation in meeting Net Zero, features in ‘Section 3: Work on Existing Buildings’. Here it states that when energy efficiency measures are installed, airtightness may be increased so ventilation should be assessed to determine what, if
any, additional ventilation provision is needed to ensure good IAQ. There is also a move to more advanced
energy efficient ventilation with Part F giving maximum SFP levels for various types of systems. By implication this pushes specification towards ventilation systems with EC motors or inverter control. For example, the energy efficient ACM100-200 and ACM250-315 mixed flow in-line fans from Vent-Axia provide ceiling mounted cooling in the summer or can recirculate the warm air from the ceiling in the winter to minimise the amount of time space heaters need to be active. Meanwhile, Vent-Axia’s Lo-Carbon T-Series fans feature EC motors and can provide background or purge ventilation and are easily fitted to an existing window or through a wall. As a whole latest revision of Part F of the Building Regulations marks a step change in recognising the importance of good IAQ and the role ventilation plays in achieving this. Whether working on a new build or refurbishment, it’s essential that energy efficient ventilation is included to ensure occupant health and wellbeing as well as helping work towards Net Zero.
Read the latest at:
www.bsee.co.uk
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