AIR CONDITIONING & IAQ


With air quality currently a hot topic, the government recently announced updated guidelines for improving indoor air quality (IAQ), thermal comfort and ventilation in schools and colleges. The new guidelines mean that architects, building services engineers and education decision makers will have to look much more closely at ventilation strategies for new buildings and refurbishment projects. Here, Jibin Kurian, product manager at FläktGroup,


discusses how they can meet new recommended performance levels


construction of tightly sealed buildings and the use of synthetic building materials and furnishings. However, in learning environments it is widely acknowledged that good indoor air quality (IAQ) plays a major role in protecting the health and supporting the productivity for both students and staff. As a result, the Department for Education (DfE) revised its Building Bulletin 101 guidance on ventilation, thermal comfort and IAQ. The aim is to place tougher performance requirements as part of the design, specification and construction of new build and existing schools. With the respective merits of mechanical and natural ventilation at the heart of the debate on improving the air quality in classrooms, what steps can schools take to ensure they have effective and appropriate ventilation system in place?


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BB101 2018 – What’s new?


Building Bulletin 101 (BB101) was originally released back in July 2006, providing guidance in addition to the Building Regulations for the adequate provision of ventilation in schools. But since then, ventilation technology has advanced rapidly, as has the insulation of school buildings.


A consultation on the revised BB101 ran in 2016, and the new update was finally published in August 2018. Updates include a requirement to control draughts more closely, and application of higher levels of air filtration, particularly in schools affected by pollution. There are also new CO2 limits which cannot be breached for 20 consecutive minutes.


As the UK is set to experience hotter summers, BB101 addresses the issue of summer overheating. Full occupancy of the school building is now assumed throughout the summer, including the holiday period. And the rules state that there should be no more than 40 hours between 1 May to 30 September when the temperature is 1ºC above the allowable maximum.


As well as new builds, the guidelines


ver the past 50 years, indoor air pollution has


increased due to a variety of factors, including the


BSEE Top of the class for air quality


also set out a major change for refurbished teaching spaces, which now have to achieve an average CO2 level of below 1,750ppm. Any future classroom refurbishment will therefore now have to include a review of the existing ventilation system to ensure maximum CO2 levels are not exceeded.


Assessing the options


In existing buildings there is a trend towards using natural ventilation to improve indoor air quality, due to the perception that it costs little to run. However, the main problem with natural ventilation is that it is affected by the weather. For example, a building using natural ventilation in the winter is purposely allowing cold air into it, putting extra pressure on the heating system, which is likely to result in inflated energy bills.


When weather conditions are not conducive to natural ventilation, mechanical ventilation becomes a much more reliable option. A major benefit of mechanical ventilation is that it will contain CO2 sensors that will control the fan speeds depending on the ventilation required – helping make the comfort levels within the building much easier to manage.


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. Furthermore, any noise from the mechanical vent heat recovery (MVHR) can be reduced by fitting silencers in the ductwork or close to the unit.


Delivering results


The new guidelines recognise that mechanical ventilation plays a key role in delivering optimum indoor air quality in schools that are exposed to high levels of noise and outdoor pollution. But with new government targets on energy efficiency and ever-tighter school budgets, another increasingly important consideration is to keep running costs down.


Modern mechanical ventilation units are now available that feature speed controllable fans that 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 air handling unit (AHU) such as FläktGroup eCO Premium can recover between 80-90 per cent of heat from the extracted air, which can be used to warm fresh incoming air. To avoid overheating in warmer weather, thermal bypass facility can control and vary the amount of heat recovered. The new guidelines are a big step forward in the drive towards a healthier environment for schools. The tougher targets for ventilation are an opportunity for education providers to take control of indoor air quality and provide students with the optimal conditions in which to thrive. By including the latest AHU technology as part the ventilation strategy, these targets can be easily met in an energy efficient way.


uUsed in conjunction with a heat recovery device, an air handling unit (AHU), such as FläktGroup eCO Premium, can recover between 80­90 per cent of heat


Read the latest at: www.bsee.co.uk


uGood indoor air quality (IAQ) plays a major role in protecting the health and supporting the productivity for both students and staff


‘


When weather


conditions are not conducive to natural ventilation, mechanical ventilation


becomes a much more reliable option


’


www.flaktgroup.com BUILDING SERVICES & ENVIRONMENTAL ENGINEER FEBRUARY 2019 19


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