One year after occupation in August 2014, the new Department of Environmental Affairs (DEA) building in Tshwane is exceeding its Green Star SA Design certification targets and elevating awareness of sustainable technologies and the benefits of a well-structured public private partnership agreement.

The contractual conditions for the DEA building differed substantially from a conventional design-and-build project because an agreement was signed between the DEA and the equity owners of a private party consortium comprising Aveng (Grinaker LTA), Kagiso, WipHold and Old Mutual, which covered the design development, construction and operational phase of the building over a 25-year period.

Green Star SA targets were incorporated into all the supplier contracts, so the tenderers were all aware of these requirements upfront. Because of the size of the project, which was developed at a fixed cost over a fixed timeframe, a lot of work was done upfront on the contract side, and there was strict project management control over the course of the construction period.

Dr Jeremy Gibberd, architect and sustainability consultant at Gauge, says the public private partnership (PPP) agreement included a mechanism for monitoring the building’s performance over the 25-year operational phase. “The private party is subject to penalties should the performance criteria not be met, so it is in their interests to avoid penalties (both in time and costs). There is therefore accountability all the way through from inception to the end of the 25-year contract.”

This process also impacted specifications for the project as everything had to be performance-based, which meant materials and systems were not chosen based on price alone. In addition, many issues had to be tied down upfront, such as ventilation, lighting, landscaping and plants, which meant the DEA became very involved in the thinking and detailing of the building.

However, Gibberd adds, the legal process of setting up the PPP as a pioneering endeavour was onerous and expensive as there were substantial upfront legal costs, and extensive negotiation required between the parties. He says such agreements could be simplified in future. Lessons from this project could be used to develop a pro forma set of standard documents, reducing the time and cost spent on the contractual process.

Lood Welgemoed from Boogertman & Partners adds: “The PPP agreement was very exciting – a very hands on, iterative process with an interdisciplinary and cooperative team. The initial requirement was for a 4-Star Green Star SA rating but, as we went through the process, we found that a 6-Star rating became achievable.”

Peter Gray of the Dijalo Property Group says the success of the PPP agreement was that everyone knew what the targets were upfront, and what their responsibilities were. Gray says facilities managers were given a set of green building operational targets they had to report on quarterly and annually. These include: energy; water; waste recycling; and indoor environmental quality.

Energy targets exceeded

The project has far exceeded the energy goal targeted in the Green Star SA Design submission of a maximum of 115kW/m2/annum, with metered readings up to the last reporting period in terms of the PPP contract indicating a consumption of just 89kW/m2/annum, including parking and tenant lighting.

Welgemoed says: “Initially the photovoltaic (PV) system on the roof was calculated to contribute 10% to the overall energy generation of the building. Between design and installation, the cost of the system came down and the efficiency of the panels increased, so the relative contribution of the PV farm increased to an anticipated 20%.”

“We now have a full year of commissioning data – it has exceeded the anticipated 20%, indicating the initial design assumptions submitted for the Green Star SA rating were conservative, as the PV farm currently generates 21,8% of the building’s energy needs,” Mike Aldous from Mott MacDonald PDNA confirms.

He says the PV system was designed to contribute over 700 000kW/year but due to the building’s lower energy consumption, the PV contribution is higher than the original design requirement. “One of the side effects of the high level of energy efficiency achieved by the building is that the building base electrical demand is too low to accommodate the amount of power produced over weekends and public holidays, resulting in the project being forced to disconnect portions of the PV system via the BMS over weekends and public holidays to avoid feeding back to the grid. This is because the current municipal metering system actually bills any feedback into the grid as consumption, as the project discovered in the commissioning phase. Until the local authorities implement a feed-in scheme, the project is unable to take full advantage of the excess PV power produced as it is effectively fully operational for only five days out of seven.”

An evaporative cooling system with night flush ventilation and perforated ceilings helped to reduce the load on the air-conditioning system. At night the windows on the first floor and at the top of the building’s atrium are opened. The heat is dissipated into the atmosphere, reducing the internal temperature in the building so that the air-conditioning can be started later the next day, and improving the indoor air quality. While modelling showed this would create a 3% drop in temperature, in reality it is closer to 7%.

Adaptable planning, also targeted in the Green Star SA credits, resulted in internal flexibility for the air-conditioning and lighting systems, so the electrical configuration could be completely changed without changing the wiring. Each of the 2500-3000 lights has a digital IP address allowing data, including the energy consumption, to be collected from each fitting.

Water efficiency

Water efficiency measures and the rainwater harvesting system implemented resulted in the consumption of 41% less water, versus the anticipated 30%.

The primary grey water processing and storage facilities, including two tanks with a combined storage capacity of 234m3, are located in the basement. The grey water system collects and reuses water from hand basins and showers, as well as from the evaporative cooling system, which dramatically increases the water input in terms of water volume to keep the system operational and improves the system’s dilution characteristics. The distribution of grey water to the toilet flushing system is independently metered to maximise the operational potential of the reused water source.

Green forerunner

With the results of the 6-star Green Star SA As-Built submission eagerly awaited, Gibberd notes the building’s success should have a knock-on effect in terms of the PPP format employed in government buildings, as well as the incorporation of sustainability criteria in new builds and retrofits.

In addition to giving the DEA credibility in terms of furthering its discussions around environmental matters with industry, this project has created talking points in government and will hopefully set a new benchmark for both local and national government projects moving forward.

By Karen Eicker

For the full article, see earthworks magazine Issue 29, December 2015/January 2016.