The credit crunch is at the top of the news agenda and whilst there’s no doubt that we are all becoming sick of the dreaded ‘R’ word, it is having a major impact on the commercial building market.
One glimmer of hope that is helping to remove some of the gloom is the Building Schools for the Future program (BSF), the biggest ever school building investment programme that aims to rebuild or renew nearly every secondary school in England. This programme, along with other initiatives like the investment in social housing not only provides some stability for the UK construction market, but also offers a massive opportunity for our industries.
Ultimately, the Government’s ambitious BSF programme aims to transform the learning and working environment in secondary education. This is not just about the construction of new, modern buildings with state-of-the-art facilities, the programme also touches on every aspect of better design that is shown to have a positive impact on pupil health and achievement.
In the past, school buildings have been considered by many within our industry in relatively simple terms, the introduction of BSF, along with legislation like the Building Regulations, means this is no longer the case.
Looking at the bigger picture, the underlining fact is that if the targets set out by the Government to reduce carbon emissions and improve the efficiency of the UK’s building stock are to be met, the whole design of a building has to be challenged. From a ventilation point of view, the most important factors are indoor air quality – achieving a clean, fresh and healthy air environment, thermal comfort and reduced transmitted noise.
Ventilation of school buildings
With buildings becoming more airtight, providing sufficient ventilation is becoming increasingly important for both new and refurbishment schools. There are a number of other factors that have to be taken into account, such as the increasing use of IT equipment, the amount of glazing used and the impact this has on natural light, and the use of lighting in the building itself. It is also important to consider what a space is going to be used for, how often it is going to be used and how many people will be using that space at any one time.
Poor ventilation is a serious issue. Excessive condensation can cause mould growth, leading to cosmetic and structural damage to the fabric of a building and can create extremely poor indoor air quality, which can lead to potential health issues for the building’s occupants. The level of carbon dioxide in classrooms will also impact pupil concentration.
A correctly designed, specified and installed system will ensure the required performance levels, help reduce carbon emissions and comply with industry regulations. CO2 should not ever be >5000 ppm with an average not >1500 ppm. At any occupied time occupants should be able to lower concentration of CO2 to 1000 ppm. When ventilation is supplied at 8 l/s per person the CO2 concentration will generally stay below 1000 ppm.
Selecting the right solution
There are a number of ventilation systems on the market from which specifiers can choose, including central plant, MVHR , natural ventilation and mixed-mode ventilation. So, which is the best solution for schools?
The common myth amongst many specifiers and contractors is that central plant and heat recovery units are the best systems. Ultimately, every new or renewed school is different, therefore it is essential as an industry that we do not get into a ‘one solution fits all’ scenario.
The answer has to be the individual systems that take advantage of the design and orientation of the school, the changing temperature throughout the day, night, and regional seasonal profiles to optimise comfort whilst minimising energy loss. The system design should have the ability to be stand-alone or integrated with renewable heat pump heating and cooling, solar thermal panels and wind energy systems to suit the application.
The Building Regulations Part F and Building Bulletin 101 govern that ‘Natural ventilation should be used for standard teaching and learning areas’ BB101 2.2. Natural ventilation is an innovative system that is widely recognised as the best way to ventilate a building as it is energy and maintenance free. However, if this solution cannot cope with the demands of the hotter summer months, then the assistance of comfort cooling through mixed-mode ventilation is the ideal top up solution to maintain a comfortable school environment all year round. A potentially more environmentally and financially sound solution than adopting a full mechanical ventilation system is to adopt a hybrid or mixed – mode ventilation strategy. BB101. 4.1.2.
Bespoke design
In response, Xpelair has developed brand new mixed-mode ventilation solutions specifically designed for schools which exceed the requirements of the BSF initiative, and allow for completely bespoke solutions to be designed for individual spaces.
Xpelair’s split level system operates via a combination of CO2, temperature and time controls, minimising energy input and reducing carbon emissions by use of free cooling passive ventilation, with summer cooling achieved by means of low energy DC fans.
Designed for installation into external and internal walls or cladding, it features market leading acoustic performance with weighted element normalized level difference of up to 38dB. This will greatly help designers keen to use natural ventilation without the problems associated with noise transference, especially from inner city areas, through open windows or noise from classrooms or corridors.
Up to six units can be managed from one controller to allow timed function, night cooling function, temperature differential sensing and manual override. Modulating controls also allow users to control the airflow passively or make up for mechanical ventilation.
This means that each room has its own individual system and auto-controls. A standard classroom of 55-60m2 with 32 occupants would typically have a single-sided system with two filtered inlet terminals at low level and two output points close to the ceiling. In the summer, auto-actuators take advantage of free cooling at night to reduce the overall temperature of the fabric of the building in readiness for the next day. In the mixed-mode, as daytime temperatures increase, the low energy fans provide assistance for the air circulation, whilst for deeper rooms, cross ventilation systems can be used to exchange heat into corridors or other areas of the building. If preferred by the design consultant the air input units can be used in conjunction with Xpelair’s acoustic stack vent arrangement using passive stack ventilation or our unique acoustically treated air transfer fan.
The energy savings of this type of system can be significant. A typical school with twenty classrooms could realise a saving of 40,000kW per annum over mechanical cooling. To complement this, the installed cost is approximately 15% lower.
Moving forward
There’s no doubt that it is an extremely exciting time for those involved in BSF getting new schools to achieve the highest levels of performance, both in design and practice. In order to do this, it is vital to adopt a partnership approach with specifiers in order to share technical expertise and achieve Best Practice.