An educated approach to ventilation
Elta Group's Ana Cross on how to balance new ventilation requirements with energy efficiency
Posted by Julian Owen | January 23, 2019 | HVAC & lighting
ventilation, elta-group, energy-efficiency, ana-cross, bb101

While it is no surprise that providing good indoor air quality and thermal comfort can have a hugely beneficial impact on health for a building’s occupants, it has also been shown to vastly improve concentration, productivity and performance.  

As the title of the guidelines suggest, Building Bulletin 101 (BB101) Guidelines on Ventilation, Thermal Comfort and Indoor Air Quality in Schools helps clarify how these factors impact school buildings and their occupants. Since its last revision, BB101 details a number of issues regarding ventilation rates based on occupancy levels, adaptive thermal comfort to prevent cold draughts and summertime overheating, and guidance on how to reduce the level of outdoor pollutants in the air supply.

In recognition of the fact that the UK suffers from high levels of air pollutants from traffic - such as particulates (PM10 & PM2.5) and gaseous pollutants (including nitrogen dioxide) - the Education and Skills Funding Agency emphasises the need for higher levels of air filtration for schools in highly polluted areas.

BB101 now discusses air filtration in considerable detail, enabling designers to confidently combine an energy-efficient ventilation strategy with higher levels of air filtration, minimising the ingress of polluted outdoor air into buildings. It furthers its guidance by recommending the use of finer filters on supply intake air streams, such as ISO ePM2.5 70% (F7) or even ISO ePM1 90% (F9). Filtration provides a means of cleaning the air supply, but also ensures that the mechanical ventilation system continues to operate at its optimum level by protecting the fans and energy recovery devices. 

The ventilation guidelines have been updated to encourage better-designed schools which offer comfortable learning and teaching environments

Balancing compliance with efficiency 

In circumstances where natural ventilation isn’t appropriate - because the outdoor air is too polluted, hot, or cold - mechanical ventilation strategies - based on energy recovery with thermal treatment and improved filtration - can be a more suitable and reliable option, due to the energy efficiency savings and comfort provided. 

Energy recovery units, in particular, help to maintain a comfortable working temperature by recovering thermal energy from any warm air inside the occupied space to raise the temperature of incoming fresh air. However, during colder periods, the heat recovered isn’t always sufficient; this is where energy recovery units with heating capability come in. Essentially, the same units can be used to deliver more heating into the occupied space, offering a more energy-efficient way of heating or cooling a space. In the summertime, these units can also recover cool air from the occupied space to help lower the temperature of the incoming air supply. When fitted with integrated controls, they can significantly reduce the unnecessary use of air conditioning by using passive measures, such as night cooling or night purge, to cool spaces.

Most important in the process of energy recovery is the use of filters to remove pollutants and consistently provide clean fresh air. Opting for mechanical ventilation with high grade filters will offer enhanced filtration, and therefore vastly improved air quality, particularly for schools located in urban areas with higher pollution levels. 

Filtration provides a means of cleaning the air supply, but also ensures that the mechanical ventilation system continues to operate at its optimum level

BB101 highlights the importance of ventilation controls in allowing end users to adapt ventilation in line with their fluctuating requirements. Ventilation systems should be able to accommodate times of low occupancy and increase ventilation for out-of-hours use, or during the summer. Controls also help to maintain acceptable indoor air quality for educational facilities by monitoring CO2 levels, while avoiding cold draughts or excessive energy consumption in the heating season. 

While there are significant benefits for improving air quality, complying with these new guidelines can be a costly exercise. To overcome this, schools should opt for energy recovery systems which boast energy-efficient features for a shorter payback period. 

Ultimately, the ventilation guidelines have been updated to encourage better-designed schools which offer comfortable learning and teaching environments. Although the updates are comprehensive, schools can comfortably comply with the guidelines by considering energy recovery ventilation with enhanced IAQ management devices; an efficient and reliable alternative to drawing energy from the mains. 

For more information on Air Design’s solutions for schools, please visit air-design.com 

Ana Cross is UK associate product manager of air handling systems at Elta Group

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