AIR CONDITIONING & AIR QUALITY IAQ – striking the balance
In our drive towards energy efficiency, are we forgetting that in creating sealed buildings, we are potentially depriving ourselves of the essential for life- air? Dave Harding, sales & marketing director at independent air movement specialist Gilberts Blackpool, explains
Y
es, we design ventilation into a building, but how often do we get it right? To make the UK’s building stock
more insulated and airtight and to reduce the amount of energy
required for heating, the objective is to reduce uncontrolled, and hence overall, ventilation. The current minimum standard permissible under UK Building Regulations (Part L) is 10 m3/ hr/m2 @50 Pa, with ‘good practice’ defined as a maximum of 7m3/hr/m2 @50 Pa and best practice as 3m3/hr/m2 @50 Pa.
Any building with an air tightness tighter than 4-5 m3/hr/m2 @50 Pa is recommended to have some form of mechanical ventilation, since windows, trickle vents and extract fans would not be sufficient to maintain healthy rates of ventilation. However, even now, almost 70% of all homes in the UK – including 41% of homes built post 1991 – do not have background and extract ventilation(1). Historically, a building would always have a degree of fortuitous ventilation through gaps in the structure. Therefore, by building sealed buildings to optimise energy efficiency and prevent leakage, we are potentially deteriorating indoor air quality(2): if the ventilation scheme is not well designed, pollutants can become trapped inside. Since Awab’s Law, there has been much talk about the need to remove damp, but it’s about the balance. We need a degree of moisture/ water vapour in the air, for the health & wellbeing of occupants and the building fabric. As an industry, it is down to us to ensure the schemes we design and install provide the right balance. People depend on us. Away from home, people do not have control over the quality of the air that they breathe. Ventilation not only needs to be designed well, and installed well, but also commissioned adequately and operated well by the building’s users. Failure in any of these aspects could lead to reduced air exchange and increases in indoor pollutants.
I would emphasise that, as part of the design and install, elements that are often not appreciated in its impact on IAQ is the type and siting of the various air distribution units. They can have a massive effect. To elaborate, take for example swirl diffusers. Their omni-directional nature means the fresh, incoming air currents rotate. If the diffusers are positioned too close together, then the air currents will collide.
Not only can that cause discomfort for the occupants, but also potentially throw airborne particles around the space rather than directing them out: think of a tornado and how it throws debris as it travels – lightweight materials such as paper can be found up to 200 miles away(3). Yet positioned correctly, and they are highly efficient at delivering high volumes of air to achieve the required air change, rapidly intermixing to maintain a comfortable air temperature and compliant IAQ. Where greater airflow control is required, a slot diffuser can provide the accuracy needed. They can also be deployed skilfully to create a curtain effect, such as over large windows to help reduce condensation by mitigating the temperature differential between the two faces of the glass. We installed a bank vertically adjacent to an atrium entrance to help balance the inrush of colder external air as people came in and out of the building. If ventilating a large open plan space, you need to optimise fresh air throw so there are no pockets where stale air nor pollutants can accumulate. Jet nozzles often provide the answer in this scenario. We are lucky today in that advances in technology have given us numerous tools to check and validate our designs to ensure they
Any building with an air tightness tighter than 4-5 m3/hr/m2 @50 Pa is recommended to have some form of mechanical ventilation, since windows, trickle vents and extract fans would not be sufficient to maintain healthy rates of ventilation.
are compliant, that the air moves correctly into, around and out of the space. The key is to work with companies that have the same values and objectives – to deliver ventilation that works!
1.
https://www.sciencedirect.com/science/ article/pii/S0360132324006577
2.
https://uk-air.defra.gov.uk/ assets/documents/reports/
cat09/2211011000_15062022_Indoor_Air_ Quality_Report_Final.pdf
3.
https://en.wikipedia.org/wiki/Tornado_ intensity
6 BUILDING SERVICES & ENVIRONMENTAL ENGINEER FEBRUARY 2026 Read the latest at:
www.bsee.co.uk
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40
