South Africa’s built environment is earmarked as a sector having a significant role to play in becoming more energy efficient and environmentally sustainable. But with a low-income housing backlog of more that two-million units, the affordable-housing sector potentially also has an important role to play in employment creation and in creating manufacturing opportunities.
Hence, there is excitement over a pilot project being rolled out in the picturesque coastal town of Kleinmond, in the Western Cape, where the first 20 of 411 greener, low-income subsidised homes are being constructed.
The Overstrand muncipality, in the Western Cape, has come on board for the project, and the implementation of the innovative tech- nologies has been funded by the Department of Science and Technology (DST).
The pilot project follows research done by the Council for Scientific and Industrial Research (CSIR), which followed as a directive from, and was funded by the DST.
The CSIR built three houses at its test site. The first was a standard subsidy house, the second a standard subsidy house, but built to conventional suburban housing standards, and the third was the specifically designed CSIR house, using what is regarded as best practice design and build techniques.
All houses provide a floor area of about 40 m2 and consist of two bedrooms, a shower, a toilet, and a combined living, dining and kitchen space.
The CSIR house can be built within the cost of a standard subsidy house plus the allowance that government adds for coastal conditions. CSIR Built Environment principal researcher Llewellyn van Wyk explains to Engineering News that the researchers looked at the standard subsidy house being rolled out by the Department of Human Settlements, and identified where opportunities existed to improve the performance of the house through the design with the least cost increase.
“For the green building movement to have credibility, it must be able to develop benefits for the poorest of the poor,” emphasises Van Wyk.
He voices concern that, at a philosophical level, the green building movement is creating a problem because it is viewed as elitist, and not for buildings that people live in, but rather for offices and shopping malls.
If, as is often purported, green office buildings can improve the productivity of office workers, it follows that a green home could, in addition to lowering operational costs, significantly improve someone’s overall way of life.
Van Wyk adds that the approach to green building should be “let’s design it right” – and this is something that needs to be taught from university level. Designers should be asking how they can design a space that will use the least amount to heat or cool, and illuminate, and so on.
“We should be striving for the least artificial intervention,” Van Wyk says, adding that one cannot simply throw money at the problem in the low-cost housing sector, and that the design issues must be dealt with thoroughly.
“Designers must not only think about the bells and whistles to make a building greener, but must also think about how to choose the most appropriate dimensions for a room, and so on.”
One must keep the performance of the building in mind, and educating occupants in building maintenance and the operation of the structure is important.
Improving the performance of the CSIR house was focused on five areas, namely the substructure, the superstructure, the roof assembly, finishes and services. The first step was to orientate the house so that it was north facing – a simple step, which allows the house to be cooler in summer and warmer in winter.
Van Wyk explains that the CSIR house removes the traditional foundational filling and creates a platform that is based on the ultrathin concrete roads which are being built in the townships. The foundation is 50 mm thick, with the sides a spade deep and a spade wide dug into the ground.
Local material is also used underneath the slab; thus, there is no need to import river sand, which also allows savings on transport costs and energy.
“This substructure method has delivered a huge saving on resources, as well as on time. It is also a labour-intensive method, and people in the community who have been trained to build roads could transfer their skills and lay the foundations,” says Van Wyk.
A standard subsidy house comprises a concrete strip foundation, foundation walls and a concrete slab with screed finish.
The CSIR foundation has saved about 1 t of concrete, compared with a standard subsidy house foundation, and the funds saved could be spent on other aspects of the house.
For the walls of the house, the CSIR method specifies hollow concrete masonry blocks, which come in sets from established suppliers, and have variations for windows, corners and beams.
The standard subsidy house uses solid concrete blocks for both internal and external walls.
“Like a Lego set, it has all the pieces you need to build a house, but builders don’t use them, and the houses aren’t designed to use the blocks, because the room dimensions are not drawn up accordingly,” Van Wyk notes.
The hollow blocks are 390 mm long; thus, the house and rooms are designed to 400-mm dimensions, allowing for 10 mm of cement between the blocks. The builders are given a simple dowel stick to place between blocks to ensure measurements are done correctly.
For the top layer of bricks, rebar is used in the block, and the wooden beam for the roof structure is bolted down. This reinforces the area where the roof and walls meet, and eliminates cracking of the walls, which is a notorious weak point of standard subsidy housing.
Van Wyk says that, because the house has been designed to strict specifications, there is no need to cut bricks or blocks and compromise the integrity of the structure. It also eliminates a large amount of waste and uses fewer blocks.
Because the blocks and bricks need to be managed differently, the Construction Education and Training Authority and the Concrete Manufacturers Association have developed a blocklayer’s certificate, for the training of artisans in the correct method to lay the blocks.
Van Wyk asserts that the thermal insulation of the roof is the Achilles heel of the standard subsidy house, because it comprises only wooden beams and a steel cover, providing no insulation.
The CSIR house includes a ceiling, which is made of a strong recycled product called Lambdaboard. This improves the thermal properties of the house significantly.
Van Wyk further explains that the beams within the roof have been orientated differently in the CSIR house and overhang the walls to create eaves on the east and west façade of the house to shade the area and protect the house during the overheated period of the day.
The direction of the roof sheeting has also been changed, so that the ridges run horizontally rather than vertically, and the sheeting has been slightly tilted towards the back of the house. In this way, when it rains, the water collects and spills down into the next ridge, finally collecting in the lower corner – where a rainwater tank is placed.
Finishes and Services
In a standard subsidy house, neither internal nor external walls are plastered, and, to prevent water penetration, the outside walls are finished with StippleCrete, a decorative coloured waterproof cement-based finish. Inside, the walls are finished with a cement slurry, which is left unpainted.
Subsidy houses in coastal areas receive an extra R7 000 allowance for plastering, and using this, as the pilot project is being rolled out in a coastal area, the CSIR house makes use of thermal plaster for the external walls, called Thermoperl.
This finish seals the building envelope and, while waterproofing it, also keeps it cooler in summer and warmer in winter.
The maintenance of this finish has been flagged as a concern in the assessment of the CSIR building, and is something that the CSIR is considering improving.
The standard subsidy house is equipped with two plug points, and not much of this could be changed in the CSIR house.
However, in terms of services, the CSIR house is able to make considerable improvements to the plumbing.
The CSIR has reduced the piping requirement by 43%, as it has clustered the services to run off a single pipe, which can be pre- fabricated and taken to the site as a modular element to be installed.
A shower is a standard fitting in the subsidy house, and is still present in the CSIR house, although, rather than being just a very shallow floor for the shower, it has been converted into a sit bath – waterproofed and with a plug, so that it can also be used for washing.
At the Kleinmond pilot project, the DST is also contributing towards putting a 100-W solar photovoltaic (PV) panel on the house, which could power three lights fitted with CFLs for about three hours at night.
The additional DST funds – about R13 000 for each house – also allow for a low-pressure evacuated-tube solar water heating (SWH) system to be placed on the roof for hot water needs, and for a rain tank for water collection.
The PV panel, the SWH system, and the rainwater tank considerably lower the need for the house to draw services from the municipality.
Thus, in addition to assisting the munici- pality with improved housing delivery, the CSIR house also assists the municipality with water and electricity service delivery and maintenance, as it eliminates a number of these problems by designing them out of the system.
Van Wyk states that, if one looks at the energy saved, in terms of materials used and in the operation of the house, and the water saved, and considers that figure multiplied by 2,1-million, which is what the housing backlog stands at, it is significant.
“I’m not saying you can cancel building a Medupi power station or a huge dam, but, perhaps, you could delay a municipality having to build another reservoir, and make local electricity reticulation easier,” he adds.
He further explains that the development paradigm facing local authorities is that they already struggle to maintain existing infrastructure – be it housing, water or electricity – and yet there is a constant need for more services. Thus, the strained carrying capacity of the existing infrastructure and constantly needed new infrastructure create a vicious cycle of providing more houses, placing strain on services.
“Build the new houses in a way that you will not need to constantly upgrade the services,” Van Wyk reiterates.
The roll-out at Kleinmond includes the full monty in terms of extras provided by the DST, and the Overstrand municipality has also decided to spend extra on the homes and use cement roof tiles, rather than galvanised steel roof sheeting.
The contractor ensured that the local labour responsible for construction underwent training for a week before the project started, and the CSIR will monitor construction as well as the project for a year after the completion of construction, by March 2011.
Van Wyk explains that the CSIR will liaise with the beneficiaries of the homes to understand what works well and, perhaps, what needs to be changed. After the monitoring and verification period, the project will be wrapped up, and then ‘debugged’ after which, hopefully, a model can be developed that government could use in other housing developments.
Research has been done on the CSIR house, comparing it with the other two houses built on the CSIR test site, and a report has also been drawn up, identifying the savings and potential weaknesses of the CSIR house.
“The results have been incredibly exciting,” enthuses Van Wyk, who adds that the CSIR now has a model that can be improved.
“We have built the Citi Golf of subsidy houses, and got the basics right; now we can look at how to refine that and build the next-generation model.”