A major breakthrough

Delivering high standards of indoor air quality is an imperative in good building services design.  Building regulations demand it, the building fabric requires it and numerous studies prove how end-users benefit from an indoor environment that boosts comfort, alertness and productivity. In the current economic and environmental climate, cutting running costs and reducing carbon also remain key priorities for building occupiers.

One area of intense activity in our sector clearly demonstrates the importance of these issues and the contribution that new ventilation technology can make in satisfying each and every one.

I’m talking about the Building Schools for the Future (BSF) programme. Set out by the Government in 2005, the BSF is a £9.3 billion Government initiative that will enable local authorities to maintain and improve all secondary school buildings in England. Already, 50 BSF schools have opened, with over 3,500 secondary schools engaged in the programme, between design and delivery.

This investment programme is underpinned by Building Bulletin 101 which provides the regulatory framework in support of the Building Regulations for the adequate provision of ventilation. It deals with the design of school buildings to meet the ventilation requirements of both The School Premises Regulations and the Building Regulations Part F (Ventilation).

With this focus on improvement and renovation to create a healthy learning environment, the local partnership teams created to manage and deliver the BSF programme have a responsibility to identify and prevent indoor air quality problems, and improve it where they can by removing moisture, CO2 and external fumes. In fact, Building Bulletin 101 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.

Increasing fresh air ventilation to prescribed levels is the solution. However, with the Energy Performance in Buildings Directive (EPBD) in mind, partnership teams must be sure that they opt for the most energy efficient solution possible. Here the answer is, unequivocally, on-demand ventilation, which is purpose-designed for this type of variable occupancy application. Now, Vent-Axia is taking on-demand ventilation one step further by incorporating high efficiency, energy recovery technology in the new Sentinel Totus D-ERV system.

Sentinel Totus is the UK’s first and only D-ERV system to be independently rated and tested to EN308. It not only recovers 90% of the energy that would otherwise be wasted but, in doing so, also takes out the need for the after heaters which are commonly required in lower efficiency ventilation systems.

The system responds to the exact ventilation requirements of a room at any one time providing the right level of supply and extract airflow only when required. At the same time, maximum energy is recovered from the extracted air (both heating and cooling) and transferred into the fresh supply air via the unit’s integral, high efficiency, counter-flow plate heat exchanger.

A range of sensors, such as CO2, PIR occupancy detection, humidity or temperature, are employed to determine the occupancy of the rooms, and manage the system’s ventilation rates accordingly. They communicate with the main Sentinel Totus unit which, in turn, drives the fan to the required speed to deliver the airflow and respond precisely to room conditions. Sensors can be combined to generate a hierarchy of control for the ventilation system with operation capable of linking in to a Building Management System for full control and monitoring, if required. A constant pressure unit option is also available, controlling centrally, based on individual room controlled dampers. 

Automatic air-conditioning and heating interlocks enable the system to optimise energy recovery performance. And an automatic summer by-pass offers free cooling when conditions prevail, also helping to reduce the use of cooling refrigerants.  A night-time purge facility reduces the start up loads for any air-conditioning plant and helps reduce over heating in summer from non air-conditioned spaces. Meeting the requirements of Building Regulations Part L2A and L2B, Sentinel Totus achieves a specific fan power at 25% of design flow rate, no greater than that achieved at 100% design flow rate.

In short, on-demand energy recovery ventilation is the answer to key questions such as ‘Why ventilate a room you’re not using?’ or ‘Why over ventilate a room with only one or two occupants inside?’ overcoming many of the issues encountered with a traditional fixed volume ventilation system. Required airflow rates can be comfortably achieved in classrooms, lecture theatres or other areas in other building types with changing occupancy patterns, bringing added value in terms of quantifiable air quality, health and productivity benefits.

Specifying Sentinel Totus D-ERV will also help public sector and commercial end-users ensure that their buildings meet EU demands to the 20% cut in energy consumption by 2010 targeted by the EPBD.

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