Striking the right balance

Amended Approved Document Part F of the Building Regulations, was hailed as a “vital step to improve indoor air quality.” David Cook explains more on what this means for energy managers

As buildings become more airtight to improve efficiency, it is essential to consider IAQ too to protect the wellbeing of inhabitants. The latest amended Part F (Means of Ventilation), which goes hand-in-hand with the latest amended Part L (Conservation of Fuel and Power), therefore set out “significant changes”, which are driving adoption of low carbon ventilation as an industry standard and improving the quality of the air we breathe in buildings. This includes the amended 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 in 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.
There are significant areas in the revised Part F that energy consultants, contractors and building services consultants working on non-residential buildings need to consider. With Part F focusing heavily on health and wellbeing a key addition to the amended document was a new section on monitoring IAQ. During the pandemic indoor air monitoring through CO2 monitors had 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 ventilation needs to be improved.
Part F therefore set out a requirement for new commercial buildings to have the means of monitoring IAQ 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 can be achieved using CO2 monitors that 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 has external levels of around 400ppm. A well-ventilated space would have average levels of around 800ppm, whereas average levels of 1,500ppm would indicate the space is poorly ventilated and action should be taken to improve the situation.
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 this should be taken into account if certain pollutants, including carbon monoxide, sulphur dioxide, and lead exceed limits as outlined in the Air Quality Standards Regulations 2010.
To combat the ingress of external pollutants in general, intakes should be located away from the source of the pollution; where urban traffic is the cause of the pollution air intakes should 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. Document F advises that mechanical ventilation may be the most practical way of achieving this.
When specifying ventilation in buildings, one way to help ensure effective ventilation that meets air quality needs is to opt for modern demand control ventilation systems. These are ideal in an office application as they automatically respond to the air quality needs of a space, supplying or extracting air only when, and to the extent to which, it is required ensuring a building is ventilated when populated.
Another key addition to Part F, which reflected 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. There is a wide range of different types of ventilation that fit this criteria ranging from more complex heat recovery ventilation systems to relatively simple in-line or wall or window-mounted fans. And finally, by utilising demand ventilation control, following the principle of ventilating only as much (or as little) as required, whichever ventilation system type is employed will operate as efficiently as possible for that system type.
The 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 is essential energy efficient ventilation is included to ensure occupant health and wellbeing, as well as helping work towards net zero.

• David Cook is technical product manager at Vent-Axia