Boilers & heating

According to ‘Building bulletin 101’, the ventilation performance standard for schools is based on the requirement to control the concen-tration of CO2 (which mainly results from exhaled air). In turn, as Andrew Peters of Whitby Bird commented in BSj (page 56, 06/06), “the concentration of CO2 in the room is the best indicator of air quality. The higher the concentration, the more stuffy the room and the harder it is for pupils to concentrate”.

The bulletin also says that the concentration of CO2 in all learning spaces, when measured at seated head height and averaged over normal school hours (ie 9.00 am to 3.30 pm), shouldn’t exceed 1500 ppm. So what options are available to building services consultants?

One option is purpose-designed natural ventilation systems, whose advantages may include the fact that they do not consume energy in the form of electricity to operate, which could equate to lower energy consumption and cost savings for the school. However, the main drawback of a natural system can be its lack of precise control of air flow, which means a school runs the risk of under-ventilation on calm, hot days and over-ventilation on cold days.

Secure night cooling is also an important consideration during the summer months. Use of refrigerant is discouraged in schools, so the ventilation system should be designed to work with the thermal mass of the building to provide effective and secure intake of air during the coolest hours of the night.

The bulletin states that building services designers in schools can use whatever ventilation provisions suit a particular building, including the use of innovative products and solutions, if it can be demonstrated that they meet the required performance standards.

Swindon Borough Council recently took this approach with the installation of a pilot system that provides heating and controlled air refreshment and ventilation for a three-classroom extension for four to seven-year-olds at the 290 pupil Haydon Wick primary school.

Sensors measure the CO2 concen-tration in each classroom and react accordingly by introducing fresh air and extracting a matching quantity of stale air zone by zone. The system makes quiet air changes only when needed according to the quality of the air in the classroom.

Integrating the ventilation system with the heat emitters was key, as it ensures that during the heating season, fresh air being brought in from the outside is warmed as it enters the classroom, eliminating cold draughts.

Teaching staff at the school have reported that classrooms are fresher and that the children stay more alert after lunch and concentrate better in the afternoons – the hardest time to teach children.