Burning issue
Top of the class for IAQ
I
n recognition of air pollution’s damaging health effects, the National Institute for Health and Care Excellence (NICE) and Public Health England (PHE) recently called on councils to take action and protect the public. From banning idling cars outside schools to introducing clean air zones, the latest guidelines - ‘Air pollution: outdoor air quality and health’ - sets out a number of recommendations that local authorities can implement to improve air quality. Bearing in mind that over 800 educational institutions in London alone are located in areas with toxic levels of air pollution according to a recent study, NICE and PHE’s guidelines can help protect hundreds of school pupils from a range of related long-term health problems.
Not only does air pollution create an unhealthy outdoor environment; it can also pose challenges for school managers working in such areas to provide a healthy classroom environment. Pollution discourages occupants from opening windows for ventilation, yet ventilation is needed to avoid overheating in the warmer months, and to ensure that indoor CO2 levels stay within the levels set by DoE’s BB101 guidelines. For this reason, BB101 recognises that mechanical ventilation plays a key role in delivering optimum indoor air quality (IAQ) in schools that are exposed to high levels of noise and air pollution.
In mid-season and winter months, when
occupants may be discouraged from opening windows to avoid cold draughts, a mechanical ventilation unit with speed controllable fans can match ventilation rates according to the amount of people in the room to optimise energy consumption. Used in conjunction with a heat recovery device, an AHU such as Fläkt Woods’ eCO Premium can recover between 80-90% of heat from the extracted air, which can be used to warm fresh incoming air. To avoid overheating in warmer weather, a thermal bypass facility can control and vary the amount of heat recovered. A mechanical ventilation heat recovery system
can also use night time air in the summer months to pre-cool the building fabric and provide a more
www.heatingandventilating.net Fläkt Woods product manager Chris Jones
comfortable learning environment when children first enter school. During daytime, cooler indoor air, chilled water, refrigerant coils or an evaporative humidifier can all lower incoming air temperature. Mechanical ventilation can also help facilitate better student concentration levels and clearer communication in the classroom by limiting incoming noise.
The units have smaller openings in the
façade compared to natural ventilation which is assumed to be fully open. Where acoustic louvres are used with natural ventilation to reduce incoming noise levels, larger openings would be required to maintain airflow, posing a security risk. Any noise from the AHU in a mechanical system can be reduced by fitting silencers in the ductwork or close to the unit. It can also be independently tested to guarantee acoustic performance and is not subject to changing weather conditions. So not only does mechanical ventilation offer a suitable choice for schools in noisy locations, but also others that suffer from poor acoustics. This could range from schools with Victorian buildings without adequate
Fläkt Woods eCO Premium AHU
As awareness of air pollution increases, Chris Jones, product manager at Fläkt Woods, examines how mechanical ventilation delivers clean air to school children in areas subject to high levels of noise and outdoor pollution. He also discusses the technology’s role in providing adequate ventilation and avoiding overheating in classrooms, in line with expected changes to the DoE’s BB101 guidelines
sound insulation, to modern multi-purpose open plan rooms affected by background noise. At the time of this article going to press, BB101 is anticipated to raise the minimum standards for IAQ, especially in mechanically ventilated buildings. According to current guidelines, CO2 levels should never exceed 1,500 ppm. Each person in a teaching space needs between 3 and 8 l/s at any occupied time. New guidelines are expected to lower the maximum daily average concentration of CO2 permitted in a teaching space to 1,000ppm, and this is to be typically achieved by supplying around 8-9 l/s/p of fresh air. It may take a long time until real progress can be made in tackling air pollution in cities and built- up areas. So despite the more stringent criteria, many inner-city schools will continue to rely more on mechanical, rather than natural ventilation. It offers all education providers the opportunity to act now to provide better IAQ and a more effective classroom environment for their students. It’s more than a capital expenditure; it’s an investment in a brighter and healthier future for our next generation.
A graphic of Fläkt Woods eCO Premium as used in a schoolroom
September 2017
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