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Meeting the challenge of carbon zero in schools
Changing your ventilation can save energy. To many outside the building services industry, it seems a contradiction but in the drive for schools to be zero carbon by 2050, it is an obvious area to consider according to Ian Rogers, sales director at air movement specialist Gilberts Blackpool
I
nevitably, new schools are already being designed and built to that target. The UK has more than 32,000 schools•. The Government plans to rebuild
or refurbish 500 over the next decade and has put in place a raft of schemes and funds to help achieve this. It means that most of the schools we are involved in are existing; our job is to make them as airy and energy-efficient as possible- no small task when you consider the diversity of internal volume and use of each space within, from a sports hall to IT suite. And we have to factor in building layout, choice of building fabric, orientation, glazing, occupancy, usage patterns, external noise levels and noise transmission, sources of air pollution, heating and cooling provisions, room pollutants and expected solar gain. BB101- the guidance for school ventilation-
prefers natural ventilation but acknowledges that it cannot be the sole solution in today’s schools. It is not just changing activities within but also the positioning of the school building itself. The ‘free’ night cooling inherent with natural ventilation can be adversely impacted in “heat islands” - densely built urban environments. Thus, we need to consider the whole ambit of techniques available to us, with BB101 preferring hybrid ventilation. Hybrid systems predominantly utilise natural
ventilation, switching to mechanical via a low energy fan only as/when demand requires: not to be confused with mixed mode which is where one space is ventilated naturally and another within the same building via mechanical means. Because hybrid systems are stand-alone, with one unit serving one zone and no need for ductwork,
HVAC FOR SCHOOLS
That in itself impacts positively on the carbon footprint, let alone capital equipment costs whether new build or refurbishment. Certain hybrid units have also been developed to work with heat pumps, which use water at a lower temperature than conventionally powered boilers. Anecdotally, we know of instances where the combination of greater heat recovery and heating capability in a hybrid system has enabled a reduction in the number of solar panels required to power the school! Hybrid ventilation systems are great for “standard” classrooms, but schools have so many other activities therein as mentioned above. Hence the growing need for mixed mode systems with the focus on natural ventilation but mechanical options stepping in as required to maintain the equilibrium. In rooms with high heat loadings such as IT
they are well-suited to refurbishment, provided there is a suitable external wall or window. Addition of transfer grilles above doorways also ventilate adjacent corridors.
BB101 points out that in older buildings, the
balance point where no heating is required can be as high as 15degrees, making them a good candidate for a further evolution- hybrid ventilation with heat recovery systems (HVHR). It is worth noting that the heat recovery
performance can, and does, vary depending on manufacturer which can have an impact on the reduction in energy consumption and the carbon footprint.
The latest development with HVHR units is the inclusion of LPHW heat coils, which enables the system to provide heating as well as cooling- to the extent that separate radiators are no longer needed.
suites, mechanical ventilation will be needed to maintain the ambient temperature and CO2 levels. Strategic placement and adjustment of the diffuser nozzles and vanes and grille blades can help ensure the airflow is precisely directionally controlled- swirl, horizontally, vertically, evenly or directionally- to avoid draughts or cold ‘dumping’. Now, there are also thermally sensitive diffusers which adjust the airflow vertically or horizontally without any electrical connection and within seconds to maintain the temperature preset- and avoid the issue of pupils complaining they are too hot or cold. It all means that now, probably more than ever, as an industry we have greater choice in how we deliver HVAC in the education sector. Remember, manufacturers have the technical knowledge of how diverse methods of ventilation interact and help ensure a cohesive integration through a holistic design approach to the diversity of environments within our public buildings. Using that expertise, in conjunction with other
devices such as computational fluid dynamics and BIM, enable designs to be validated and adjusted to balance the required criteria. The key is to work with trusted professionals in the field who can advise and support you to deliver the best HVAC scheme possible within your constraints.
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https://www.statista.com/statistics/283575/ number-of-schools-in-the-united-kingdom/
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