Solid Green offices: class-leading efficiency

By Ilana Koegelenberg

The Solid Green offices in Johannesburg achieved an impressive 6-Star Green Star rating, thanks to the help of a radiant cooling system.

SG00 1 800Note the radiant cooling panels on the ceiling of the Solid Green offices.
Image credirt: Solid Green

Solid Green’s offices achieved a 6-Star Green Star SA Interiors v1 As Built Rating, demonstrating ‘World Leadership’.

The building is located in the centre of Rosebank, within walking distance of the Gautrain, Rosebank Mall, a taxi rank, and a bus stop, providing alternatives for staff and visitors to commute to the office building. Other transport methods include a branded electric vehicle with charging facilities and electric bicycles.

An ‘Occupancy Users Guide’ and ‘Comprehensive Transport Plan’ have been developed for the Solid Green interior fit-out to enlighten staff with regard to transport facilities, incentives, and local amenities available in the area, as well as to inform them how to use building services to the optimum potential.

A green lease has been implemented for the Solid Green office to monitor and report on energy usage, water consumption, and waste generation by staff and building visitors. The results are continuously displayed in the foyers via the Solid Insight web application, making building users aware of their environmental footprint.

An enhanced ASHRAE commissioning process was implemented for the fit-out as a prerequisite for the Leadership in Energy and Environmental Design (LEED) Commercial Interiors v3 Rating achieved.

Radiant cooling was implemented for efficient space cooling as well as renewable energy to offset  peak demand.

The project commenced in January 2015 and was completed within a month in February 2015. The budget of R1 800/m2 was met.


The HVAC client brief had a requirement for the following:

  • Innovative thermal comfort
  • Class-leading energy efficiency
  • 35W/m2 radiant cooling capacity
  • Maintain radiant temperature under 26°C
  • Fully naturally ventilated space.


A reversible heat pump operates via a heat exchanger to a closed two-pipe hot/chilled water circuit, which reticulates to the office’s radiant cooling panels. The water temperature is controlled by desired room condition via control panels in rooms.

This system cools the occupants of the room, not by cooling the air, but by radiant cool energy that is exchanged with occupants. This way, you achieve comfort in naturally ventilated and higher air-temperature environments by using less energy.

The radiant cooling system is incredibly efficient and it achieves a 40–60% saving compared to a traditional air-based system.

A Daikin split-bloc integrated hot water and heating and cooling 5kW heat pump was installed, however the hot water function isn’t being utilised. It’s called a split-block because the hot water heat exchangers is separate to the compressor (unlike with a monobloc where it’s all together).

A total of 24 600 x 600 Ecophit standard graphite ceiling panels from Lidner were installed. These were fully customised to the clients’ needs. The panels are powder coated and fitted out with rear-mounted 75mm steel copper piping.


Hot and chilled water reticulation into an existing building was a bit of a challenge and the piping was reticulated via external cladding.

The import of components was also a challenge, as the panels are not manufactured locally.


The radiant cooling system is incredibly efficient and it achieves a 40–60% saving compared to a traditional air-based system.

Higher chilled water temperatures and more direct addressing of thermal comfort via radiant temperature make the system very sustainable. It also provides better indoor environmental quality through improved thermal comfort and better acoustics. No air is recirculated.


Radiant cooling systems circulate cool water through ceiling-, wall-, or floor panels. ‘Coolth’ from that water is then absorbed by occupants and interior spaces according to the dynamics of thermal radiation. These radiant cooling systems, which are popular in Europe, are not as yet a thing in South Africa.

Radiant cooling systems can be more efficient, more comfortable, more attractive, and more healthful than systems that circulate air. Over their lifetimes, they are also less expensive to own and operate.

Given these advantages, radiant cooling is poised to make a big splash in other markets in all climate zones. Currently, there are two important barriers to its entry into local markets: a lack of familiarity with radiant cooling technology, and lingering memories of moisture control problems experienced by a few pioneering systems installed decades ago.

The latter barrier should be mitigated by recent advancements in sensor and control technology. The first barrier, local industry unfamiliarity, will probably diminish as information becomes more widely available about successful applications all over the world.

Healthcare facilities, which especially benefit from the way radiant cooling systems separate comfort cooling from ventilation functions, may lead the way.


 Owner / Developer   Solid Green
 Architect / Designer   TC Design
 Project manager    Solid Green
 Consulting engineer: Mechanical  Solid Green
 Contractors   Main building  iBw
 HVAC & R  Tech Butler
 Wet services  iBw
 Electrical   iBw
 Product suppliers  Lindner radiant panels   Tech Butler
 Solar panels  Emergent Energy
 Heat pump  Daikin 

Click below to read the July 2017 issue of RACA Journal



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