Issue 76Closing the Performance Gap in Schools

In the face of climate change, and tight school budgets it’s increasingly important to provide reliably comfortable environments for education, without the additional carbon and financial costs. FCBStudios Researcher Joe Jack Williams explains how.  

Simple design ideas for a reliable, comfortable school environment.

Comprehensive systems such as Passivhaus or Enerphit can provide demonstrable benefits, but aren’t easily applied to the wide range of existing school buildings in the UK.

An alternative is to look at low-tech, passive design principles that can help create a comfortable environment. Using these approaches, the cost of carbon-intensive systems can be largely avoided. Another clear benefit is the increase in intelligibility of the building, avoiding “black-box” systems that cannot be readily understood by the staff and students; a simple opening window can be operated by a student, whereas a centralised mechanical system can confuse even seasoned facilities managers. 

The following steps are recommendations that can be used in new and existing schools alike, representing significant ways potential overheating in schools can be managed, based on work undertaken by FCBStudios, the CIBSE School Design group, the DfE, and Ann Griffin, RIBA Client Adviser and Director of Architects Collaborative. 

Cross-Ventilation 

With simple opening windows or vents, teachers and students can easily understand how to bring in fresh air, particularly when coupled with simple air quality indicators to guide when they need to be operated. However, typical classrooms only have windows down one side of the room, with no exit route for the fresh air beyond the way it came in (called single-sided ventilation), which can lead to the back of the classroom feeling hot and stuffy while the space next to the windows may be too draughty. Instead, a cross-ventilation strategy with attenuated ducts, either up through the roof or into an atrium, can ensure that the air can reach across the whole space, removing stale air, but also keeping the occupants cool and comfortable in hot weather. Vertical roof-mounted ducts can be carefully inserted into existing schools to enable the crossflow, but need to take into consideration fired control and acoustics. 

The right sized-room 

When thinking about any occupied space, there are two key dimensions to consider: the height of the room and the depth relative to the external wall. Classrooms with higher ceilings, over 3.2 metres, help through increasing the stratification of the air, where warmer air pooling occurs above the heads of the staff and students where it will cause no discomfort. This also helps with air circulation, particularly with rooms that have single-sided ventilation. In spaces with a suspended ceiling, simply removing the false ceiling and exposing the soffit can have a significant impact but may require additional acoustic rafts to avoid reverberation issues. 

By keeping rooms less than 7.2m wide (from the external wall), they are able to operate as single-sided ventilated spaces. This is key during cold months, when some cross-ventilation strategies may not work as effectively. Where rooms are wider than 7.2m, it can be possible to rearrange furniture to keep the occupied space within this sweet spot, for example, by rearranging storage to make a longer, thinner room. 

Buffer Spaces 

In recent years there has been an increased awareness of adaptive thermal comfort, recognising that the way we perceive temperature is relative not absolute. On hot days, we’re more tolerant of higher temperatures, and vice-versa on cool days. One way to enhance this effect is to create buffer spaces between outside areas and learning environments, where the staff and students adjust to the changing environment. In primary schools, this can be a cloakroom that prevents sudden gusts of hot/cold air when the doors open, but also enables a shift in mindset as the students transition from outside to inside. In secondary schools, the buffer spaces become more transient, but can be connected to atria or open plan dining spaces. The entrance to these large spaces, especially when connected to atria need to be well designed as, without careful consideration, on windy days the draught through entrances can be uncomfortable. 

Thermal Mass 

An increasing concern is overheating in classrooms. With high numbers of students in relatively small spaces against a backdrop of a warming climate, this is recognised as a significant factor in comfort and wellbeing for the students.   

A simple way of reducing the temperature of the rooms during the day is to capture the coolth at night and use it to cool the space during the day. By including thermal mass in the room coupled with night ventilation, the night air reduces the temperature of the thermal mass, ready for the next day, where it absorbs the heat, creating a more stable temperature in the room. 

Thermal mass can be as low-tech as exposing the concrete soffit. If that isn’t possible, thin concrete panels can be installed on the ceiling/soffit, which only needs to be 50mm thick to work efficiently. Once thermal mass is introduced into the room, a night ventilation strategy needs to be devised that will ensure the building remains secure but also allows the fresh air to circulate across the thermal mass. Restricted windows or secure louvres are a common way of ensuring windows can be left open at night.   

Post-Occupancy Evaluation 

Schools are constantly evolving organisations, as are the buildings that house them. Often it can be helpful to have a view on how the building currently serves the school and understanding whether the operation could be more efficient to reduce costs while increasing comfort.  

The above recommendations are relatively simple and have a lasting effect on the performance of the building. They can all be retrofitted into existing buildings, but their efficacy will be significantly helped through expert advice from building designers, whether architects or engineers.  

Joe Jack Williams

Images

1. Highfield Humanities College. © Will Pryce
2. Diagram to show seasonal classroom ventilation strategies

 

 

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