Schools are under increased pressure by Government to reduce their carbon footprints, however, this cannot be achieved at the cost of good indoor air quality. Nygel Humphrey, Product Marketing Manager – Non-Residential at Vent-Axia explains how on-demand ventilation, coupled with high efficiency energy recovery successfully manages air quality as well as reducing carbon footprints and energy costs.
With schools accounting for 2% of UK greenhouse gas emissions and 15% of the country’s public sector emissions, the Government is keen to cut their carbon footprints. However, caution needs to be taken when it comes to reducing carbon in schools to ensure emissions reduction isn’t achieved at the cost of good ventilation. Currently, the schools sector is undergoing the ambitious construction programme, Building Schools for the Future (BSF), which aims to see almost every school in England rebuilt or refurbished by 2020. The BSF programme offers an ideal opportunity to construct low to zero carbon schools, but the challenge is to create a healthy learning environment, facilitated by excellent indoor air quality where problems with moisture, CO2 and external fume are eliminated.
Building Bulletin 101, which provides the regulatory framework in support of the Building Regulations for the adequate provision of ventilation in schools, specifies limiting CO2 levels within teaching and learning spaces to 1500 parts per million. However, fresh air supply rates per person in schools are often so low that CO2 levels are well above this recommended level, leading to adverse health effects and also impacting on the learning performance of pupils. In 2004 research from the University of Exeter on The Effect of Low Ventilation Rates on the Cognitive Function, concluded that in a classroom with high CO2 levels students are likely “to be less attentive and concentrate less well on what the teacher is saying which may possibly over time lead to detrimental effects on learning and educational attainment.”
Just over a year ago research from Reading University and University College London revealed that new energy efficient schools were being designed to be more airtight to reduce heat loss, but as a result the schools had appalling ventilation rates with CO2 levels exceeding targets. This research followed the Commission for Architecture and the Built Environment’s (CABE) worrying findings that drew specific attention to HVAC issues with classrooms as part of its detailed review of 40 proposed designs for schools under the BSF initiative.
So how can consultants help schools achieve a balance between reducing their carbon footprints and maintaining good ventilation? Recent research undertaken in a sample of recent school projects points to schools that have on-demand mechanical ventilation installed as showing the lowest energy consumption while providing good indoor air quality. On-demand ventilation therefore both improves indoor air quality in schools and is a solution to the energy/ventilation conundrum. With traditional fixed volume ventilation the system is either on or off irrespective of the number of people in the room. Here, you run the risk of creating a mediocre and unproductive classroom environment through over or under ventilation with a resulting waste of energy.
Instead, demand ventilation works by responding to the exact ventilation demands of a room, supplying or extracting air only when and to the level it is required. The system is activated according to sophisticated control and sensing options. A range of sensors, such as CO2, PIR occupancy detection, humidity or temperature, are employed to determine the room air quality state and adjust the ventilation requirements automatically in the classroom, and manage the system’s ventilation rates accordingly. The sensors communicate with the main unit which, in turn, drives the fan to the required speed to deliver the airflow and respond exactly to classroom conditions. Sensors can be combined to generate a hierarchy of control for the ventilation system and ventilation system operation can also be easily linked in to a Building Management System for full control and monitoring, if required. Therefore, only the energy that is needed to ventilate is actually used. Demand ventilation control also limits summer gains and winter losses as only the required ventilation is delivered based on occupancy and indoor air quality need, reducing summer overheat and heating losses in winter.
However, on-demand ventilation is just the first step to reducing school carbon emissions. As we move towards zero carbon buildings the energy efficiency improvements needed to meet these carbon goals will result in buildings becoming increasingly air tight. As a result newer ventilation technologies, such as mechanical ventilation with energy recovery, will increase in popularity to increase efficiency by recovering heat/cool and substantially lower carbon footprint.
Therefore the latest on-demand ventilation systems, such as, Sentinel TOTUS Demand Energy Recovery Ventilation (D-ERV), provide especially impressive energy savings because they integrate 90% energy recovery into the ventilation system. This type of system extracts the energy from the warm, stale air taken from classroom areas before it is exhausted to outside whilst fresh, incoming air is preheated via the high efficiency plate heat exchanger and supplied into the classroom. The energy recovery process is proven to utilise up to 94% of the heat energy which would otherwise be wasted to outside. The result is a massive further boost to the energy performance credentials of the ventilation system especially in larger school buildings.
This type of system also offers schools further energy saving potential. An automatic summer bypass will take advantage of any free cooling available when the ambient temperature is below the room design condition, something found particularly during the Spring and Autumn seasons. The TOTUS system also incorporates interlocks for associated heating and cooling equipment installed to optimise energy recovery potential and eliminate any possibilities of systems conflict. There is an installer settable night-time purge facility which will purge the room overnight in the summer to reduce start up temperature/loads and help reduce over heat in summer from non air conditioned spaces.
Since an on-demand system is automatically controlled, it also eliminates the need for manual intervention by the teachers. At the same time, it improves comfort, keeping CO2 levels within prescribed regulatory limits for school classrooms, as defined by Building Bulletin 101.
At a time when many schools are feeling pressure to cut their carbon emissions but also improve indoor air quality consultants can offer them the solution – on-demand ventilation can bring significant advantages creating a productive and energy efficient academic environment.
For more information on Vent-Axia's Sentinel Totus D-ERV, please click the following link: http://www.vent-axia.com/range/sentinel-totus-d-erv.html