House Rhino is a showcase of design, technology and materials that push boundaries in home innovation and energy savings.House Rhino – perched on the edge of a Kloof in Crossways Farm Village, overlooking the Van Stadens River gorge outside Port Elizabeth – is an off-grid, zero energy, zero waste house serves as an industry example, while changing the scene for homeowners who are serious about sustainability.
“I see it as an on-going experiment,” says Brian van Niekerk, House Rhino homeowner and managing director of the Rhino Group of Companies.
The house’s location in Crossways Farm Village – a functioning dairy farm and eco-village – allowed for it to be developed off-grid, says developer, Dr Chris Mulder of CMAI Architects.
And the municipality was supportive when it came to planning, said architect Steff Mulder of CMAI Architects.
No architectural compromises
House Rhino has two wings – a bedroom and living space wing linked via the kitchen, which leads out onto a courtyard.
“The design benefits from a combination of active and passive design features, including a northern orientation, skylights and double-glazed facades on the northern front,” says Steff Mulder. The link between the two wings has a green roof with recycled plastic planting boxes for growing vegetables.
“We are harvesting rainwater, not only from the roof space, but we’ve also implemented a drainage system below the hard-surfaced driveway, parking area and around the residence,” says Van Niekerk.
By using Hydromedia, a porous concrete product, the rainwater catchment area for the household is effectively amplified.
Sarel Bam, water systems and treatment manager at the Rhino Group, says rainwater draining through this medium is diverted to an underground drainage system and inline filter.
The water is channelled to 300 000 litre rainwater storage tanks. The medium’s high permeability means rapid absorption of rainwater, increasing the volume of water captured.
From the storage tanks, the water passes through a series of filters, including ultra-filtration and UV filtration processes.
A secondary harvesting system has also been implemented, where all black and grey water, along with organic kitchen and garden waste, is fed through an Agama biogas digester. The natural gas produced is used for cooking and delivers enough gas for four hours’ cooking time.
The overflow from the biogas digester is routed to a small polishing plant, where it is treated through a trickling filter and collected in a 2500l water tank.
“Once collected, it is treated with ozone prior to use for irrigation,” says Bam.
Completing the water systems loop is an aqua garden, including a reed bed system, which purifies water for the natural swimming pool.
The water system can handle up to eight permanent residents. Based on an average consumption of 150 litres per person per day, Bam says the water systems in place contribute to water savings of approximately 400 000 litres per year.
House Rhino is powered by 74 photovoltaic (PV) panels mounted on the building roof, each with a generating capacity of 230W.
The PV system has been designed to support a daily energy consumption of 50kW and is supported by zero-maintenance batteries.
“The total storage is able to run the house for one and a half to two days,” explains Van Niekerk.
Monitored by a building management system (BMS), non-essential appliances are switched off during low energy days. The system is further specialised by separating the Grundfos pool pump from the main PV system, running it on its own 1000W PV system.
Taking into account seasonal variations, the PV system has generated in excess of 100kW, with winter generation averaging at 45kW.
Should energy generation exceed demand, excess will feed into the development’s electrical grid.
House Rhino Built with Aruba
About 75% of House Rhino was constructed of interlocking Aruba blocks, an insulated concrete form (ICF) system. This green building technology is widely used in the United States and Europe, but is still fairly unknown in South Africa.
According to the project’s structural engineer, Dave Visser of Nieuwoudt & Co, this polystyrene form filled with concrete is internally reinforced, both horizontally and vertically. To meet structural standards, “engineers can choose how to reinforce the wall with the cavity filling”, says Visser.
They chose Aruba blocks made of Neopor, which “specifically gave us a thermal resistance (R-value) of approximately 2.9, compared to the 0.9 of a conventional brick wall”, says Van Niekerk. “The insulation factor is roughly three times that of a conventional wall.”
Main contractor John Baines of Shield Homes says it’s the first time they’ve worked with Aruba, “and it has been a learning curve for the entire team”.
Effective heating and cooling
Although underfloor heating is common, House Rhino makes use of a less common application. The water-based under-floor heating is primarily driven by solar energy and internal fire combustion. As backup, dual heat pump technology is available.
The final indoor flooring is polished concrete. “That way, we’ve got a very good transfer of energy,” he says. “No energy is wasted though a carpet or other floor covering.”
A thermal tower extracts warm air, cooling House Rhino passively. When in operation, the heat pump produces cold water as a by-product.
“This cold water is stored in an insulated 2500 litre tank – the cold water battery – available for use as required,” he says. House Rhino uses the excess energy from the heating system to run a fridge and air conditioning unit.
The full feature appears in the August – September 2014 issue.