Green building: Energy efficiency pays dividends

January 15th, 2015, Published in Articles: Vector

Tucked away just off busy Grayston Drive in Strathavon, Johannesburg, is a facebrick office park that does not appear to be very different to the many other stylish developments mushrooming in the area.

The three-storey Upper Grayston Office Park on Linden Road is, in many respects, quite a remarkable development, especially its blocks E and F, whose design and build are not only saving the owner on energy costs but which are changing tenants’ everyday behaviour (see Fig. 1).

Building the 2500 m2 Block E cost R27-million – a price tag which included R3-million in green enhancements, of which R500 000 was aimed at improving energy efficiency. Back in 2011, the developers of the office park, Brydens Commercial Properties, were so confident of their building’s environmental credentials that they applied to the Green Building Council of South Africa (GBCSA) for Green Star SA certification.

Fig. 1: The Upper Grayston Office Park.

Fig. 1: The Upper Grayston Office Park.

In January 2012, the council awarded block E a four-star green building rating. However, the scores the independent assessors gave the block were so close to the threshold for a five-star rating that Brydens decided to submit a second application and, in October 2012, block E was duly acknowledged as a five-star Green Star SA building.

Brydens director Ron Henderson explains that, while it made commercial sense for his company to pursue the Green Star rating route, the lessons learnt at the Grayston Office Park can be applied not only by developers of new office blocks but also by owners of existing buildings. Block E’s return on initial investment proves that money spent on energy efficiency can be recouped quickly and translated into very substantial ongoing savings.

According to Henderson, any new office development in South Africa must deliver a projected energy consumption of no more than 80 W per m2, but Brydens was confident of achieving a sustainable score much lower than this requirement.

Brydens targeted 50 W per m2 and realised immediately that, to achieve this, they would have to focus first on air-conditioning as heating and air-conditioning typically account for almost half the total energy consumed in office buildings.

How to use this building

The developers of the Upper Grayston Office Park have compiled a user-friendly guide explaining to all stakeholders how their building works – and how they can help make it even greener.

Following is an excerpt from the 30-page Block E User’s Guide:

  • The air-conditioning system installed at Upper Grayston Block E consists of a variable refrigeration flow system with heat recovery.
  • When in the cooling mode, indoor units are supplied with cool refrigerant. The amount of refrigerant flowing through the unit is controlled via an electronic expansion valve located inside the unit. When the refrigerant enters the coil, it undergoes a phase change (evaporation) which extracts heat from the space, thereby cooling the room.
  • When in heating mode, indoor units are supplied with hot gas refrigerant. Again, the amount of hot gas flowing through the unit is controlled via the same electronic expansion valve. As with liquid refrigerant, the hot gas undergoes a phase change (condensation), which releases heat energy into the space.
  • The energy-recovery system can provide cooling and heating simultaneously to different parts of the building. This feature has the potential to deliver maximum energy savings. Furthermore, a heat-recovery system can transfer the heat extracted from those spaces requiring cooling to areas demanding heating – reducing energy requirements and operating costs.
  • The air-conditioning controllers will be strategically positioned for easy access by the building occupants. Each controller will have a wired interface to the indoor unit serving that specific space and can adjust all user variables to provide the optimum comfort level for the space, i.e: Unit operation on/off; room temperature setting and operation mode: ventilation/cooling/heating/auto mode.
  • Fan speed control: slow/medium/fast/auto fan speed.

The company chose a mixed-mode system, with the air-conditioning switched on when the temperature outside is too hot or too cold, but switched off with tenants opening their windows and doors when the ambient temperature reaches the “sweet spot” between 19 and 23°C.

The system devised for Brydens was elegant and relatively inexpensive. Temperature gauges on the roof of block E are linked to sets of green and red lights which are clearly visible to tenants throughout the building. When the temperature outside is between 19 and 23°C, green lights are illuminated, the air-conditioning is switched off and tenants are encouraged to open their windows.

In addition to implementing an environmentally-friendly air-conditioning system, Upper Grayston’s development included energy-saving light fittings and motion detection which ensures that lights only remain on when particular parts of the building are occupied.

Encouraging tenants – and their employees – to be aware of their energy consumption, Brydens installed an automated billing system which meters sub-divisible areas so that tenants are aware of their precise usage history of power for lights, computers, equipment and, especially, air-conditioning.

The energy savings achieved at block E clearly demonstrate that an upfront investment in systems that lower electricity consumption makes financial sense. Whereas the company targeted 50 to 55 W per m2, the actual consumption is today approaching 38 to 39 W per m2.

In its first full year of operation, electricity savings amounted to 230 000 kWh – a saving on electricity consumption of approximately R172 000 per annum in 2012 terms. This translates to a payback period on the R500 000 initial energy-efficiency investment of just 35 months.

Henderson says the automated billing system is appreciated by tenants because they believe it is transparent and encourages them and their staff to think proactively about ways to save electricity. This green way of thinking and behaving is encouraged by a screen in the building’s lobby displaying the building’s real-time usage.

One particularly innovative measure implemented at block E was a user’s guide which explains to everyone working in and connected with the building how the green measures work and how they can contribute to the effort.

Energy efficiency specialist Dr. Tsakani Mthombeni says South African landlords are increasingly engaging with their tenants to find mutually beneficial energy-saving solutions. He describes Upper Grayston as a particularly innovative solution involving and empowering tenants to take responsibility for their energy consumption.

To Mthombeni, mixed-mode air-conditioning systems are an ideal solution for older office buildings where windows and doors can be opened to the outside.

Through the upfront expenditure on energy-saving measures, block E has already proven that such investment makes financial sense. There have, however, also been less predictable benefits.

Being a certified Green Star building has helped to market the property as would-be tenants are increasingly attracted to environmentally-friendly properties. Brydens has been so encouraged by the energy, water, emissions and other savings achieved at block E that it plans to take its achievements further in the new block F, which will incorporate photovoltaic panels delivering 15% of the building’s electricity requirement.

The company anticipates seeking a six-star rating for Block F, an accolade that would signal the building’s “world leadership”.

Contact Andrew Etzinger, Eskom, Tel 011 800-5316, andrew.etzinger@eskom.co.za

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