FOCUS: EDUCATIONAL SERVICES
With the recent Clean Air Strategy placing more focus on indoor air quality (IAQ), coupled with the latest updates to the Building Bullen 101 (BB101), Ana Cross, associate product manager, Air Handling Systems – UK at Elta Group, puts forward the case for mechanical venlaon with improved filtraon in educaonal buildings to help balance the new requirements with energy eciency
t’s no surprise that providing good indoor air quality (IAQ) and thermal comfort can have a hugely beneficial impact on health for a building’s occupants, but it has also been shown to vastly improve concentration, productivity and the academic performance of staff and students in educational buildings. While the latest Clean Air Strategy focuses predominantly on air quality in the home, it is a positive move towards a world that acknowledges IAQ as a major issue. While this has widely been accepted as a way to establish a favourable learning environment, the challenge now is to ensure buildings are optimised for both air quality and efficiency. As the title of the guidelines suggest, BB101 Guidelines on ventilation, thermal comfort and indoor air quality in schools, covers the specific requirements for ventilation, thermal comfort and indoor air quality (IAQ), and how these services impact school buildings and their occupants. Since its last revision, BB101 now 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.
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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 it provides.
In recognition of the fact that the UK suffers from high levels of air pollutants from traffic, such as particulates (PM10 and PM2.5) and gaseous pollutants (nitrogen dioxide), the Education & 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 to minimise 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 per cent (F7) or even ISO ePM1 90 per cent (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.
uAir Design’s PREMA units can maintain good IAQ and comfortable temperature levels
Balancing compliance with efficiency
In circumstances where natural ventilation isn’t appropriate, either
Energy recovery units in particular help to maintain a comfortable working temperature in school buildings by recovering thermal energy from any warm air inside the occupied space to raise the temperatures of the incoming fresh air. However, during colder periods of the year, the heat recovered isn’t always sufficient which is where energy recovery units with heating capability come in. Essentially, the same unit can be used to deliver more heating into the occupied space, offering a more energy efficient way of heating or cooling a space for extra comfort. 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, these energy recovery units can significantly help to reduce the unnecessary use of air conditioning by using passive measures such as night cooling or night purge to cool spaces. What’s most important in the process of energy recovery is the use of filters to remove pollutants and consistently provide clean and fresh air, which can aid concentration and productivity. 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.
The 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 period. Controls also help to maintain acceptable indoor air quality for educational facilities by monitoring CO2 levels while avoiding cold draughts and excessive energy consumption in the heating season.
Why monitor CO2?
Increasing levels of CO2 in a confined space such as a classroom, will affect
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the health and welfare of its occupants. This is deemed as one of the best occupancy sensors and therefore widely recognised as an indicator of ventilation rates required inside buildings. So, monitoring CO2 can ensure that acceptable levels of ventilation for the health and welfare of students and teachers, is maintained at all times. Not only this, it helps control moisture, save energy and reduce greenhouse gases. Where possible, carbon dioxide sensors should be used to save energy through monitoring and demand control of ventilation systems. It is also important to consider variable occupancy - for large spaces that have alternating and highly variable occupancy levels, such as canteens, gymnasiums, auditoriums or multipurpose rooms, CO2 control is also an ideal way to control ventilation here. Normal classrooms are also subject to unoccupied periods due to lunch hours, after- school clubs or away days. It is estimated that a space that is only 80 per cent full can reduce ventilation costs with CO2 controlled ventilation.
Designing school ventilation systems of the future
While there are significant benefits for improving air quality, complying with these new guidelines can be a costly exercise for schools. To outweigh this cost, schools should opt for energy recovery systems which boast energy efficient features for a shorter payback period. For example, those with more efficient fans will consume less energy. Ultimately, the ventilation guidelines have been updated to encourage better designed schools which offer comfortable learning and teaching environments for students and staff. Although the updates are comprehensive, schools can comfortably comply with these guidelines by considering energy recovery ventilation with enhanced IAQ management devices as an efficient and reliable alternative to drawing energy from the mains. For more information on Air Design’s solutions for schools, please visit:
www.air-design.com BUILDING SERVICES & ENVIRONMENTAL ENGINEER APRIL 2019 29
uVenlaon guidelines have been updated to encourage beer designed schools which oer comfortable learning and teaching environments
BSEE A winning formula for modern school ventilation
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The ventilation guidelines have been updated to encourage better designed schools which offer comfortable learning and teaching environments
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