KNX maximises potential for light balancing

With the advent of controllable light sources, like LED, and the capabilities of open platform KNX intelligent building technology, Light Balancing optimises indoor comfort and saves energy at the same time. It must be considered as an integral and critical design element of both new buildings and in refurbishment projects, says Adriaan Jongepier of KNX UK and Somfy

The use of Light Balancing solutions to help achieve optimum comfort for building occupiers and to optimise energy savings for lighting has been pioneered by Somfy and Philips. Somfy has unrivalled experience in solar shading automation and façade management controls whilst Philips’ lighting solutions create productive and attractive work spaces at the lowest possible energy usage. The two companies are now working closely together to promote the concept of Light Balancing to architects, consulting engineers and all building stakeholders.  

Lighting, heating and cooling accounts for around 75% of the total energy consumption of a commercial building and by maximising the use of daylight, integrated light and solar shading control you have the potential to save as much as 70% on energy for lighting and 25% on energy for HVAC (these are indications for a south-facing façade with actual savings heavily dependent on building type, orientation, location and use.)

Natural light

A major trend in today’s office design is to create natural spaces that bring well-being without wasting precious energy resources.  Natural light is more desirable than ever and people prefer to work in well-lit spaces with an exterior view.  As a source of illumination, daylight is absolutely free of charge but it also has disadvantages as bright sunlight can cause unwanted glare and raise a building’s temperature – both of these reduce comfort levels.

To achieve the right balance between energy savings and comfort, Light Balancing has been developed as an integrated solution that can be applied globally to all types of buildings including offices, schools, hospitals, art galleries and laboratories.  The general and task lighting needs of these different types of building vary greatly, but the principle of Light Balancing can be applied to all of them. 

The Philips and Somfy proposition is a solution that combines exterior daylight control with interior lighting.  Light Balancing is the act of balancing the natural (direct and indirect) light from the sun and electrical lighting, in order to achieve high indoor comfort levels at low energy usage. These can be in conflict.  Whilst the sun provides free natural lighting, it also provides thermal energy, leading to solar gain within buildings that has to be managed. The impact of the sun depends upon a number of factors including the building’s location, orientation, the time of year, the time of day, the percentage of glazed façade, type of glass and other factors. Light Balancing takes all these factors into consideration.

Ideal environment

A building’s façade links the outside to the inside of a building.  Effective management using the façade will include balancing the influence of the available external light with the use of internal lighting systems, controls and HVAC systems to create the ideal indoor environment.  All of this can be done including consideration for factors such as legislation, construction guidelines and occupancy patterns.

The correct selection of the solar shading system together with glass and shading characteristics, to control and filter natural lighting, is key.   All solar shading systems can be controlled by motors that use KNX technology as the control system, with the net result being a smart system that optimises the use of available external lighting.  As a result, artificial lighting is only added on when it is needed, where it is needed and by whom it is needed with presence detectors, timers and lighting control systems also controlled by KNX.

In larger new build and refurbishment projects, controlling a Light Balancing solution over a KNX network is the way forward.  Intelligent lighting and occupancy sensors in each room can be used to control energy efficient LED lighting, dimming it when more natural light is available and switching it off when no-one is present. This information is shared over the network with the solar shading controller that operates the motorised roller or Venetian blinds to maximise the use of daylight and save on artificial lighting and HVAC energy costs.

With HVAC, the main issues within a building are those of solar gain and internal heating loads.  By using (in winter) or blocking (in summer) solar energy in the right way reduced capital investment in HVAC systems can be achieved through the specification of smaller capacity appliances/boilers which will also have reduced operational costs.

Complete interoperability

KNX really scores because of the complete interoperability of KNX building services devices. Using the vast KNX open standard product portfolio, façade products can be integrated seamlessly with other building services and their performance can be monitored.  The information can be diagnosed via the internet or LAN to provide a complete real time picture of energy consumption and appliances can be adjusted and managed accordingly.

Light Balancing should ideally be considered at the start of the design phase of a new building.  At present, the design of the lighting system for a building falls somewhere in the middle of the design process – lighting is a necessity and therefore often not given sufficient in-depth consideration.  All aspects of Light Balancing need earlier design phase attention to make sure that its benefits are to be achieved. 

With the lull in new construction projects over the last few years, the refurbishment market has been more buoyant and looks set to be so for a number of years.  Therefore retrofitting Light Balancing as part of refurbishment projects is also important if we are to achieve the reduction in CO2 emissions that we are aiming for. The retrofitting of energy efficient lamps, the introduction of lighting control systems and the incorporation of automated shading to prevent solar gain can bring immediate reductions and promote further energy savings by allowing HVAC systems to be run at lower levels. It is not unrealistic to suggest typical payback periods of just 3-4 years.

Light Balancing projects such as the installation at the Tour Sequana in France, has ensured that targeted energy consumption levels have been met.  In addition, incorporation of this solution in the HQE (Haute Qualité Environnementale) environmental rating procedure, helped obtain the target of 10 on the performance level for visual comfort.  

The management of natural light and artificial light ensures the best level of indoor comfort in terms of light levels and glare prevention.  Maximising the use of natural light has a positive effect on wellbeing and this has been prioritised thanks to the good light transparency of glass, automated solar shading and the smart lighting.

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