Ed Richmond, Business Development Manager from natural ventilation specialist Passivent, explains how close collaboration with manufacturers and the consideration of natural ventilation strategies as early as possible can help create school designs that are comfortable, compliant, sustainable and cost effective.
Ensuring a good supply of fresh air to classrooms is important to the wellbeing of staff, students and the building itself, and yet there are many lessons to be learnt about how schools can be ventilated more effectively and efficiently.
Any conversations around ventilation in schools must be informed by the requirements of Building Bulletin 101 ‘Guidelines on ventilation, thermal comfort and indoor air quality in schools’ and Building Bulletin 93 ‘Acoustic design of schools – performance standards’. The choice of ventilation system must also meet Building Regulations, including new stricter targets on ventilation in Part F, conservation of energy as outlined in Part L and the acoustic requirements set out in Part E.
As well as achieving compliance with the necessary standards, the chosen ventilation strategy should also contribute to a reduction in both carbon emissions and operational costs over the whole life of the building.
Natural ventilation can provide the answer. It is possible to devise a fully natural ventilation strategy that is compliant with BB101 and BB93 and does not require fans in classrooms, therefore, helping to reduce both operational and maintenance costs. However, early engagement is key. Ventilation product manufacturers must be consulted at the concept and design stage, and the whole building design needs to be taken into consideration, especially for new-build projects. Only then can the full benefits of natural ventilation be realised.
The natural choice?
Put simply, natural ventilation is the method of ventilating an internal space without the requirement of fans. Such systems are reliant on natural forces including external-to-internal temperature difference, wind pressure and buoyancy – essentially the force that makes warm air rise. However natural ventilation must be considered at the design stage, especially for new-build projects, to allow for cross flow of air, stacks and general planning of air paths and circulation throughout the building.
A bespoke approach is also required as different areas of the school will have specific requirements. For example, whereas large sports hall and atriums lend themselves to a displacement ventilation strategy, ICT suites will be at a greater risk of overheating and different air filtration levels will be needed for science laboratories. Through early engagement with the supply chain, natural ventilation can be considered and, if appropriate, ‘designed in’ to as many areas as possible.
By reducing reliance on fans to ventilate a space, natural ventilation systems consume less energy and with stricter environmental targets and rising fuel costs, this is a major benefit. Such systems can also help maintain a comfortable indoor temperature, which is fully compliant with BB101 by tempering the incoming air. This can be achieved using a heating coil, or by placing inlets behind radiators. During summer months, night-time purging can be enabled. This allows the building to be cooled down whilst the building is unoccupied and avoids overheating the next day. Thermal mass can also be used to ensure a more constant internal temperature.
Where there are high internal heat gains, natural ventilation can be used in conjunction with air conditioning where the system will work passively for as much of the year as possible and the mechanical system will only be used when needed.
Saving more than just energy
As well as lowering energy consumption, natural ventilation can also offer significant long-term savings in terms of reducing both operational and maintenance costs, and space requirements. Also, the capital cost of a natural ventilation system is usually less than a mechanical system, although there may be some additional construction costs required. When looking at the whole life of a building, a natural ventilation system is typically the least expensive strategy.
A sound argument for natural ventilation
As outlined by Building Bulletin 93 and reinforced in Part E of the Building Regulations, acoustic design is a key part of any school building, and ventilation systems must comply with these strict requirements. Natural ventilation removes the requirement for noisy fans within classrooms, making it an excellent choice for schools and particularly those that have a high intake of SEND children. The other health and wellbeing benefits of natural ventilation are vast and as there is no mixing of stale room air, they can also help minimise the spread of viruses such as COVID-19.
Opening up design potential
Another benefit of adopting a natural ventilation strategy is the aesthetic value they can offer. Conventional mechanical systems, which incorporate fans and mixing chambers, must be contained within conspicuous housings. This can impact on headroom clearance and also daylighting. This is because the units need to be installed at a high level, therefore, potentially blocking glazing and affecting lux levels.
Natural ventilation systems can work in conjunction with other strategies when needed. In situations where there are high levels of external pollution, filtration of the air would be required, and due to the high pressure drops of air filters this would demand a mechanical system. When overheating is a concern, a mixed-mode system, which combines the benefits of natural ventilation and mechanical cooling, may be the best solution.
For refurbishment projects, or when there is a need to ventilate classrooms individually, rather than having to consider the full ventilation strategy of the school, then hybrid ventilation systems are effective owing to their ease of installation and compliance with BB101 and BB93. Hybrid systems feature low-power fans, which help to distribute air around the classrooms and have a range of operational modes including passive, boost, mixing and heating. In ‘passive’ mode, hybrid units can provide low levels of ventilation without the use of any fans.
Realising the vision
As many schools can benefit from the specification of a natural ventilation strategy, it is important to consider it as soon as possible in the design and planning stage. Drawing on the expertise of suppliers such as Passivent, who can offer a range of both natural and hybrid ventilation solutions, will also ensure that the most appropriate solution can be identified. Through supply-chain collaboration and early engagement, natural ventilation can help breathe new life into the design of more schools across the UK.