Make classroom air quality a priority

The change at Westminster brought about intense speculation over the future of the Building Schools for the Future programme and, as anticipated, George Osborne’s emergency budget led to many building programmes falling foul of the government’s austerity package, with a further 75 construction projects hanging in the balance, dependent on the outcome of October’s Spending Review.

However, it stands that the existing Building Bulletin 101 (BB101) directive, which provides the regulatory framework in support of Building Regulations for the adequate provision of ventilation in schools, remains on the statute book and it is vital that CO2 levels continue to be monitored, regardless of whether planned overall refurbishment packages are cancelled.

The importance of good ventilation and fresh air quality in the classroom cannot be understated. With the initial implementation of BSF, the Zero Carbon Taskforce was established, to steer schools to a zero carbon existence by 2016. However, as well as the drive to reduce emissions, BB101 specified that a safe CO2 level in the classroom of 1,500 parts per million, must be maintained, in order to avoid adverse health effects and an impact on the learning performance of pupils.

Recent research published by the University of Reading and UCL demonstrated that a move towards airtightness, in order to reduce heat loss, had a staggeringly adverse effect on levels of CO2. Previous European studies on air quality, conducted in the late 90s, in which 800 students completed health symptom questionnaires while a computer-based programme scored their ability to concentrate, at the same time measuring CO2 levels in the classrooms, found that high CO2 levels were strongly related to student health symptoms and performance. This research was supplemented by the Technical University of Denmark which, in 2005, found that, by improving classroom ventilation in a Danish school, the performance of work by children could be substantially enhanced.

Effective monitoring

The evidence of these studies on air quality, supported by additional CABE findings in the UK, led to school design quickly moving to incorporate wider ranges of HVAC technology, such as on-demand ventilation. To achieve optimum results, though, on-demand ventilation has to be paired with effective monitoring of CO2 levels and this is an area in which Sontay has conducted a great deal of product development, culminating in the launch of the GS-CO2 range of CO2, temperature and humidity monitoring devices.

Offering full BB101 compliance, today’s sensors combine ease of operation with real-time monitoring and the ability to adjust ppm CO2 levels instantly – key to their successful and efficient application in the day to day running of schools. For example, Sontay’s range of sensors allow teaching staff to accurately monitor air quality and make adjustments without leaving the classroom and without the intervention of either maintenance staff or a central monitoring system – significantly increasing efficiency in operation.

Instant control

This user-friendly approach to air quality control is achieved through features such as easy to read, LCD CO2 concentration indicators, changing colour depending on the surrounding environment, and, with Sontay’s system, a unique ABC continuous calibration algorithm that adjusts an NDIR infrared sensor to accommodate for drift prevalent in other sensor types. Should readings warrant adjustment of the ventilation system, instant and accurate control is at the fingertips of teaching staff, via a simple wall-mounted or desktop control interface.

Crucially, from a maintenance perspective, the automatic calibration element of these modern sensors takes away the need for manual adjustment and, in larger school or university complexes, optional communication devices allow connection via Modbus protocol to the building’s central BMS, for added overall efficiency.

Overall efficiency

This advance in building controls technology has brought about significant advance in both the efficiency of air quality control systems for educational buildings and also in helping to create a productive and energy efficient academic environment – an element of school building management that continues to be a priority in these turbulent political and economic times, with the guidelines of BB101 remaining a constant.

CO2 monitoring – the facts

CO2 based demand ventilation, an enhanced method of control, allows the regulation of ventilation on a zone-by-zone basis, similar in principle to conventional temperature control. However, regulating air quality is vital to commercial building operators and a CO2 sensor is far more critical than a basic temperature sensor.

Currently, the majority of buildings use dampers which are set to provide a fixed amount of outside air (commonly for the life of a building) and the design, commissioning and maintenance must be carefully undertaken to ensure the duct distribution system can deliver the right amount of fresh air to each zone, based on intended occupancy. Where this traditional set-up falls down, in today’s climate, is that reconfiguring the air distribution, to account for changing occupancy requirements or office churn can mean major structural work.

Stand-alone CO2 sensors, as well as providing actual CO2 measurements, also give indication of occupancy by registering increased levels of CO2 seen during operating hours, compared to a lower, relatively stable ambient, during non-occupancy. A much more versatile solution, this can be used to give ventilation-on-demand, rather than relying on the more common fixed occupancy time profile, and result in even greater energy and cost savings.

With CO2 demand ventilation control, demand tends to be based on how the building is operated rather than how it was originally designed, giving added flexibility to control.

A simple system would see sensors placed in each zone so that air for each zone can be regulated based on actual occupancy and CO2 level. This is analogous to temperature control in that a sensor in each space measures and regulates the delivery of warm or cool air to achieve set point.

Common, and valid, reasons for employing CO2 based demand ventilation are energy savings which inevitably lead to cost savings, environmental responsibility, the wellbeing of the occupants of the building and the prevention of sick building syndrome and crucially regulatory compliance – EH40/2005 and Building Regulations.

There are also numerous benefits which include the fact that only the required amount of fresh air is brought into the building, reducing the amount of energy required to condition it. Using return air enthalpy heat recovery will further reduce these conditioning energy requirements. In addition the minimum amount of water vapour is brought into the building, reducing the risk of fabric damage and because CO2 levels can allow an estimation of occupancy numbers, this allows you to control the volumetric flow of conditioned air

With ever more stringent regulations (including Building Regulations Part F 2010 and Ventilation of School Buildings BB101) coupled with rising energy and CCL costs, the importance for operators to plan CO2 based demand ventilation has never been greater.

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