Heating and Ventilating

It can be challenging to meet the climate control needs of multi-tenanted buildings or large communal facilities with diverse uses while also ensuring comfort, energy efficiency and lower carbon emissions. Martin Passingham looks at how technological advances have revolutionised VRV capabilities.
Until now, there has been an assumption that VRV systems are only suitable for certain types of buildings. But recent technological advances mean that these assumptions are simply no longer true. Because of variable air volume's (VRV's) modularity, it is often perceived as 'one step up' from a split or multi-split system - and therefore most suitable for buildings of up to 3,000 sq m. In reality, the latest VRV systems can be applied on a much greater scale, to create fully integrated systems for buildings of any size.

In fact, it is when VRV systems are designed as a whole building solution that they can offer the very highest energy efficiencies and carbon savings. Because VRV varies the refrigerant volume within the system to match the building's precise requirements at any moment, only the minimum level of energy is required to ensure that each area maintains its set temperature, thus saving energy costs and reducing carbon emissions. Indeed, the very latest generation of VRV heat pumps incorporates variable refrigerant temperature control, which automatically adapts the system to the individual building and climate requirements, for even greater energy efficiencies.

What is more, a genuinely versatile VRV heat recovery system, operating in balanced mode to manage climate control over an entire building, can increase energy efficiency even further.

A typical office building may require both cooling and heating simultaneously, hot water storage for washrooms and kitchens. With the indoor units in cooling mode, a typical Coefficient of Performance (CoP) of 3.97 can be achieved. In milder conditions, when 75 per cent of the indoor units are in cooling mode, with 25 per cent in heating mode, the efficiencies rise to CoPs of 5.57. But when the system is fully balanced between heating and cooling, efficiencies can increase to as much as 10.07.

However, to achieve these market-leading CoPs, it is vital to analyse a building's multiple requirements, usage patterns and varying occupancy levels right from the start. This allows design of an intelligent solution that optimises energy efficiency and heat recovery.

But analysing a whole building's needs in advance does not mean that VRV is inflexible. In fact, VRV provides greater flexibility to meet current and future client requirements, because the system can be designed, built and commissioned floor by floor. It can be introduced zone by zone and tailored to the needs of each building tenant throughout a phased refurbishment programme. Because each floor - even each room - can be individually controlled to maximise energy efficiency and prevent energy waste, VRV is ideal for buildings with multiple tenants, which may have vacant areas and variable periods of high and low usage.

The integration of a VRV system with the latest intelligent control systems can again increase energy efficiency even more. For example, the latest innovations in intelligent controls are capable of allowing users to set system schedules on a weekly, monthly and annual basis. These can take into account holidays and seasonal variations in demand throughout the year, as well as different tenants' requirements, ensuring the system is being operated in the most energy efficient way.

All of these technological advances mean that VRV systems can provide unrivalled energy savings. According to Franklin + Andrews, one of the world's leading construction economists, running costs for VRV heat recovery systems are up to £6.25/sq m of gross floor area. This compares highly favourably with a two or four-pipe fan coil system, which can cost as much as £8.75/sq m and £10.75/sq m of gross floor area respectively - a 40-72 per cent increase on running costs compared with a VRV heat recovery system.

A VRV system is more space efficient than a chiller too, because it requires much less plant space. For example, Franklin + Andrews estimates that a two or four-pipe fan coil system could take up around 7 per cent of the overall lettable floor area of the building, while a comparable VRV-equipped building would take up between 3-5 per cent. This means that VRV allows developers to maximise the rental space, by requiring 29 per cent less plant space than a chiller system.

Of course, cost savings must be matched by savings in CO2 emissions too, as designers strive to meet ever tougher targets for emissions reductions in the years ahead. A framework of continuous improvements has been set with a new version of the Building Regulations due out in October 2013, an expected change in 2016 and a final revision in 2019. This means that by 2019, all new buildings must deliver zero carbon emissions from the energy required for heating, cooling, hot water and lighting. These challenging targets will require considerable innovations to improve on current practices.

Additionally, many organisations and local authorities use BREEAM as a mandatory design standard to ensure that both new build and existing premises meet the exacting requirements for CO2 emission reductions. For example, the healthcare sector has designated that all new buildings must meet a BREEAM Excellent rating and existing building stock must achieve a Very Good rating.

Again, heat pump technology can assist building designers in meeting the requirements of BREEAM by delivering heat into a building in an energy efficient, controlled way. According to BREEAM criteria, specific credits can be given for integrated services and building management systems. Further awards for innovation are also possible, depending on the system design.

To achieve the highest level of credits for system design, Integrated Environmental Solutions (IES) offers a new Daikin Dynamic VRV Systems Sizing Tool within the IES Virtual Environment (IESVE). This software enables architects and engineers to evaluate the best options to lower building energy use easily, by accurately simulating annual loads, power input and efficiencies delivered by such systems.

// The author is product manager, DX at Daikin UK //