With buildings accounting for up to 40 percent of CO2 emissions worldwide, the design and operation of commercial buildings is crucial. ROBERT MAYER from the Blind Manufacturers Association of Australia (BMAA) discusses ways in which automated shading systems can significantly increase the efficiency of any commercial building through optimised façade performance.
Facility Management: Given that such a large percentage of energy consumption worldwide is in buildings, how can automated solar shading assist with increasing the efficiency of a building?
Robert Mayer: There are a number of factors to consider when looking at the way that the façade contributes to the efficiency of a building. These include the productivity of the occupants and the direct operating costs of the building.
Factors that influence the productivity of the occupants include: temperature, which should be within the ideal comfort zone of 20–24 degrees Celsius; glare, which should fall within the 1:3:10 ratio; and indoor air quality. In Australia temperature management has the highest impact on the direct operating costs of the building.
Automated solar protection uses a combination of sensors, timers and sun tracking algorithms to ensure that the internal or external blinds of a building are in the optimum position to reduce the solar heat gain and reduce the load on the HVAC system of the building. In addition, motorised windows can be used with great effect to give fresh air to occupants during the day and to assist with cooling of the building at night. A façade designed with an automated solar shading package can result in a reduction on the required cooling load of more than 45 percent over the course of a year when compared to a building without solar shading.
In addition, significant energy savings will be gained with a fully automated shading solution over the more common manual solution. Manual blinds, while more effective than no solar shading solution, are dependent upon the behaviour of the building’s occupants. Generally, occupants will not operate a manual blind unless they are uncomfortable. This is likely to be at the time when the HVAC system is already operating at peak capacity. It is often said that a manual blind is in the wrong position 50 percent of the time compared to a blind that is part of an automated solution.
There are a number of simulation tools available that will model the performance of the solar shading solution in a given building and provide the potential energy savings.
FM: We have seen in recent years solutions developed by glazing suppliers that will reduce solar heat loadings. How do these compare to automated solar protection?
Mayer: While it is difficult for me to comment on the exact nature of these solutions, generally the tinted glasses being used have limitations in that they reduce passive solar heating of the building in cooler months. It can be shown that the ideal solution is to use a clear, untinted glass and combine this with automated solar shading. Non-dynamic sections of the façade such as tinted windows or fixed louvres have no ability to adapt their physical characteristics to changeable environmental conditions such as sun, wind, rain and clouds. Automated solar shading utilising timer or sun tracking functions can be programmed to allow solar radiation to enter the facade when desired to passively heat the building or to block the radiation under peak HVAC loadings.
FM: What are the differences between internal and external solar shading options?
Mayer: Generally, an external shading solution such as external sunscreens or external venetian blinds will offer the highest levels of shading, thereby reducing heat transfer through the glass. These products are usually limited by the size of the building, as they require access to be able to clean and maintain them, so they are not a solution for high-rise office towers. There is a variety of internal window treatments available that will offer a varying degree of shading efficiency according to the material being used and the way the are fitted onto windows. The density and type of material will affect its performance, as well as the gap of air between the blind and the window: in extreme climatic conditions this can be a very important factor that will affect the performance of the blind.
FM: We’ve discussed the benefits of automated solar shading for commercial buildings and the increases in occupant productivity that it can deliver while reducing energy costs. What are the control options available for automated solar shading?
Mayer: There are two main options for a fully automated commercial building façade: a full building management system (BMS) or a stand-alone façade management system. Each one has its benefits. A full BMS is one single system that controls the HVAC system, lights and blinds, among others. These systems can be costly, complex to set up and if a particular part fails then problems could arise if all the systems are down. A stand-alone façade management system such as Somfy’s Animeo has the advantage of being more cost-effective, and if one system in the building is out of order another system can compensate. For example, if the air-conditioning fails, then not only are the blinds unaffected, but they can also assist in compensating for the AC system being down.
There are many levels of automated systems, ranging from a simple sun or light level sensor to more complete systems that could feature sun tracking, timers for when the building is not occupied, and presence detectors, allowing unoccupied offices to revert back to an energy saving mode. Dedicated façade management systems can also use wall-mounted or hand-held radio remote controls to give manual control which help to reduce wiring in the building.
FM: What are the solutions available for retrofitting an existing building.
Mayer: This is a harder question to answer but the main constraint regarding retrofitting automated solutions is the ability to run electrical wiring from the controllers to the motors in the blinds. In a smaller installation such as a single façade or small commercial building, a radio solution might be considered. This would only require wiring to power the motors and all other components such as the switches and sensors would be radio controlled and communicate directly with the receivers in the motors.
If there was more flexibility for running wiring – say, if the building was being completely renovated – then in most cases a stand-alone façade management or building management system could be considered. There are members of the BMAA that would be able to advise on the most effective automated shading solution for any commercial building.
Robert Mayer is the chairperson of the BMAA Blind Energy Rating Committee and the managing director of Somfy Oceania. With 20 years’ experience in the blind industry, Robert has participated in the growth of automated shading systems and is passionate about delivering the best possible solar shading solutions to building