Designing in energy efficiency

With ambitious Government targets putting pressure on developers to focus on energy efficiency in order to ensure that all commercial buildings are zero carbon by 2019, the pace of innovation for sustainable technologies has never been more dynamic. For those involved in the construction sector, there is an added pressure to ensure that they lead by example and can demonstrate the validity and workability of a low carbon approach in practice.

However, while finding the right combination of energy efficient technologies, renewable energy sources and sustainable materials is challenging enough in a new build, in a refurbishment, blending state of the art thinking on carbon reduction with existing bricks and mortar is even more taxing.  When the building in question is also listed, limiting the scope and scale of redevelopment, achieving a significant reduction in carbon footprint whilst maintaining the character of the original building is even more of a tall order.

However, that’s exactly what international consulting engineers Arup, has achieved at the company’s Scottish office, Scotstoun House in a BREEM ‘Excellent’ rated refurbishment. And they’ve done it by combining sustainable energy sources, smart design features and low energy technologies with a state-of-the art building control system that monitors, visualises and controls heating, hot water, ventilation, cooling and lighting systems to keep energy usage to a minimum.

Future flexibility

Scotstoun House was designed by Arup Associates to suit the company’s own requirements and has been its Edinburgh office since 1964. The company decided to redevelop the building to create a contemporary environment that would provide sufficient space for its current and future needs but, during the design stage of the project, Historic Scotland placed a Grade B listing on Scotstoun House, imposing a number of constraints on the scheme including retention of existing walls and elements of the internal furnishings. This forced the project team to take an innovative approach to creating the company’s aspirational office environment whilst preserving key elements of the existing building.

The development involved refurbishment of the existing office and outbuildings along with a new extension, and sustainability needed to be achieved alongside a world class commercial environment with both wow factor and future flexibility. It was for this reason that the scheme’s project manager, Arup Scotland’s Senior Engineer, Douglas Wylie chose a Jung KNX building control system and KNX integrator, Seeland Systems Integration, was brought in early

in the design process to translate Arup’s wish list into a deliverable intelligent BMS system.

Enhanced control

The building is entirely naturally ventilated and it has been designed to ensure that thermal comfort goes hand in hand with energy efficiency. Thermal mass incorporated into the ceiling construction and solar powered Windcatchers that provide natural ventilation of internal meeting rooms highlight the cutting edge nature of the scheme’s sustainability specification while solar tubes have been used extensively throughout to reduce the need for artificial lighting. The glazing has also been selected to optimise light transmission (73%) whilst minimising solar gain.

The project includes a Sustainable Urban Drainage System and a biomass boiler with low energy consumption appliances used throughout along with energy efficient plant and building services systems.

Critical to the success of the building’s energy efficiency aims is the Jung KNX system, which provides the energy metering, monitoring and targeting for the building. Based around a Jung Facility Pilot system that allows centralised control, monitoring and visualisation of the building’s temperature, domestic hot water consumption, ventilation, cooling, DALI lighting system and window operation, the KNX system records operational data for review and analysis. This allows the building’s management team to access real time information about Scotstoun House’s energy performance and adjust system settings as required.

The Facility Pilot installation allows the Arup team to control, visualise and monitor the BMS functions from a wall mounted, touch screen unit, which enables the building to be controlled on a zoned basis and also offers pre-programmable scenes so that the building’s settings can be changed to adapt to different requirements depending on the time of day, time of year or occupancy levels. For this installation, the system was even designed to incorporate an outdoor weather station linked directly to the Facility Pilot controls.  As a result, the windows will close automatically if the wind speed is too high or open if the interior temperature exceeds the pre-set maximum level.

Integration of the KNX controls with the external weather station supplements the range of sensors commonly found on a KNX building control system with real-time responses to changes in climatic conditions. As a result, both the thermal comfort and energy efficiency of the building are enhanced.

Greater comfort

The refurbishment of Scotstoun House was not only designed to create a more energy efficient building but also to provide a healthier work environment for staff and visitors and the work done to reduce the need for electric lighting, heating and mechanical cooling was central to achieving both objectives. The extensive use of light tubes to introduce more natural light not only reduced the use of artificial lighting but consequently reduced the production of heat from the lighting system allowing the natural ventilation strategy to work by eliminating the need for mechanical cooling and reducing overheating. Because both the lighting and the natural ventilation systems are automated on the KNX system, changes in lighting and cooling can take place as and when required without manual intervention, enhancing the work environment and reducing conflict.

All the windows are controlled by actuators linked to temperature and CO2 sensors and the glazing used allows 70% of the sun’s light to enter the building but only 30% of the energy. The natural ventilation system was designed with the help of detailed computational fluid dynamics (CFD) calculations which revealed how the air flow would behave in the new building as compared to the old building and this was used to map heat gain patterns and determine the sequence of automated window opening. For example, the main road on the east side of the building generated some road noise through the windows facing it so these were programmed to be opened last. Fortunately, thanks to the design of the building with an internal atrium replacing a former central courtyard, cross flow of ventilation is good, allowing this structured sequencing of window opening.

Proven success

With Scotstoun House, Arup successfully took a Grade 2 listed building originally constructed in 1964 and converted it into an A-rated energy efficient, contemporary office suite. This success has been quantified thanks to a thorough analysis of the energy performance in the refurbished building as compared to the old building, carried out by a Masters student from Herriot Watt University as part of a research study.

The project demonstrates the pivotal role that BMS systems can play in maximising the value of energy efficient design and technologies. In this KNX installation, easy monitoring and visualisation is combined with flexible controls, so that the marriage between the built environment and the way in which it is managed is even more successful.

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