Greener city living through interwoven systems
Environment Response Architecture (ERA Architects) achieved a completely autonomous, Johannesburg based home, by carefully integrating the architectural design and services, and considering each element of the home, and how to reduce its impact on the environment.
During the design process of house Jones the following environmental issues needed to be taken into account; Energy use, water consumption, construction waste, biodiversity and GHG (Greenhouse gas) emissions.
To prepare the site for the new House Jones, the existing home that could not easily be made thermally efficient was carefully soft stripped. All re-useable items like doors, windows, cupboards, roof coverings and timbers, and smaller items like electrical and sanitary fittings were donated to charity. The remaining masonry shell was crushed onsite and reused as back-fill and for raising the building platform on site. Reclaimed paving was reused in service areas. Extensive preservation and re-use of top soil and existing planting was applied. In this way, no waste was carted off site to landfill waste dumps.
ERA also implemented environmental management clauses in the construction contract to make sure that the building process was non-polluting. Waste generated during construction was to be sorted and recycled, while soil had to be protected from any contamination while mixing cement or cleaning solvents and equipment. Substances such as paints, solvents, sealants, adhesives etc… had to be low toxicity and as far as possible, low VOC.
Building materials for the house were chosen for thermal performance, recyclability, low maintenance and maximum lifespan. Wherever possible, materials were sourced locally to ensure a shorter travelling distance from suppliers.
Like all of ERA’s buildings, the local climate and site context were used to develop the design strategies in order to harness whatever natural energy systems are already at play. For example, a thermally massive structure was used and exposed internally to harness the natural diurnal temperature swings of the Highveld climate. Exposed concrete soffits and masonry interior walls create a high internal mass that in turn stabilises the interior temperatures. However the exposed concrete soffits are articulated with dropped ceiling bulkheads to define space and allow for both hidden and recessed lighting design. This approach epitomises ERA’s approach to design; conceived in building performance and enhanced with architectural design features that combine to create richly defined and articulated spaces and aesthetics.
House Jones generates its own electricity during daytime by using a photovoltaic (PV) panel system on the roof that generates excess power for the home. This system feeds the inverters and UPS located in the “power plant room” that carefully and safely feeds excess electricity back into the Eskom grid, effectively lowering the home’s energy consumption by turning the meter “backwards”. No batteries are used, and at night the house draws from Eskom; in this way Eskom acts as the house’s battery. A diesel generator is available should there be no Eskom power available at night. ERA decided that this was a more environmentally responsible approach than attempting to store electrical energy in batteries that are environmentally difficult to produce and dispose of, and have an unpredictable and short life span.
Only gas stoves and ovens are used for cooking requirements, and low energy LED light fittings and appliances are used throughout the house. Large double glazed windows provide a soft and well distributed daylight to all interior spaces.
A solar thermal system of collector panels on the roof generates heat energy in a 1000 litre well insulated stainless steel tank located in the “water plant room”. This SEG tank is filled with water heated by the sun to 90oC and acts as a heat battery for all domestic water and space heating requirements of the home. Domestic hot water is heated through a heat exchange drawing the most energy from the top of the SEG, while the water based under floor heating is fed by the same energy battery from the cooler bottom half of the tank. The system was optimised for winter collection as the heating requirements in winter are obviously greater.
Cooling requirements for the building are met by three evaporative cooling towers that ventilate the house during summer. These towers were built in natural stone, and used to generate a designed aesthetic and again, create an architectural identity. One of the main design concepts of the building was the idea of “bubbles of micro-climates” that surround the house wherever the internal living spaces open onto the exterior. These are created by planting climbing on robust steel cages attached to the building that can support the weight of the large volumes of soil in the suspended planter boxes that are needed to avoid the roots freezing in the cold Highveld winters. These planted structures also minimise the summer sun penetrating the building and maximise the winter sun for additional heating. The plants were carefully selected for their deciduous and evergreen qualities, (depending on their location), their shape; climbing, draping or shrubs, and their scents and attractiveness to biodiversity.
ERA takes water conservation seriously and achieved this through collecting and recycling. During the rainy season roof level rainwater is collected with leaf shedders and first flush diverters and stored in four 10 000 litre tanks. These tanks are maintained at a minimum level during winter by a borehole, and wait for the rainy season to refill them completely. The borehole is intended to be used as sparingly as possible. The collected rain water is filtered in 3 stages and used in all but three outlets in the house, catering for almost all its water needs. Council water is also filtered on site and delivered to three potable taps. The system has a fully operational divert system for either supply to be used exclusively.
The house treats its own sewerage and recycles its waste water on the site. All waste water is treated in a 3 phase anaerobic septic tank and an above ground aerobic system; from there it is fed through a constructed wetland to purify the water even further. The recycled water is then stored in the dilution dam where it is mixed with the subsoil drainage and paving runoff and used for irrigation purposes.
House Jones has enhanced the local bio-diversity through the design of its garden and wetlands system. All vegetation was carefully selected and located to maximise the attractiveness of the garden for different species. The plants provide nectar, nest building materials, attract insects and create many different areas where birds, insects and even frogs can make a home. Indigenous fish and plants were introduced to kick-start the ecology. The cascading rock waterfalls and wetlands oxygenate the water while it is permanently re-circulated in the wetlands and dam system.