News that the Building Engineering Services Association (BESA), along with other trade bodies, is calling for a specific standard for IAQ (indoor air quality) in the UK is a very welcome development. In fact, it is astonishing that no such standard for IAQ already exists, given the importance of IAQ to the health of both occupants and building fabric.
BESA’s CEO Paul McLaughlin wrote in H&V News: “We believe that the best and most practical approach is to create the industry’s first comprehensive IAQ standard. This would help engineers and their clients put an IAQ strategy in place – and demonstrate to the government and building managers how this problem can be tackled.”
As the European Ventilation Industry Association (EVIA) points out: “As buildings are getting tighter and better insulated in order to reduce uncontrolled energy losses and increase their envelope performance, the air exchange by infiltration goes down to near zero.”
It has been observed that this is a particular problem in retrofitted buildings, where the building envelope has been upgraded without considering the possible effect on ventilation. The building operator could then have a considerable challenge in restoring acceptable IAQ.
For example, if a central mechanical ventilation system, comprising an air handling unit and ductwork already exists in the building, then increasing its capacity or extending its distribution will inevitably be expensive and disruptive.
An alternative is to use localised mechanical ventilation with heat recovery (MVHR) units installed within each space and connecting to the outside through a wall or roof, via short sections of ductwork. This avoids major disruption to the building and would often prove to be more cost-effective.
This approach lends itself equally well to retrofit and new-build projects.
It is likely that any such standard for IAQ will be implemented through the Energy Performance of Buildings Directive (EPBD), which is currently under review. Energy efficiency will therefore be a key criterion and any MVHR unit selected for a project should offer the following:
- High efficiency heat recovery.
- Inverter control of fan speed for demand controlled ventilation.
- Low Specific Fan Power.
- ‘Free cooling’ option when outdoor temperatures permit.
MVHR units mounted in the ventilated space also need to operate with low noise levels, especially in areas such as classrooms, libraries and offices.
In addition, filtration of both incoming and outgoing air not only removes contaminants from the air that room occupants breathe, but also protects the heat exchanger surfaces from fouling and thus safeguards their performance.
SAV’s AirMaster demand-controlled MVHR units meet all of these criteria. They are easy to maintain and straightforward to retrofit in existing buildings, with a typical installation time of less than four hours.