The Green Building | Case Study

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Concrete masonry used in building a better environment

The Green Building was initiated by Sarah Ward and Mark Borchers of Sustainable Energy Africa, in collaboration with Mike Schroeder, an architect working with the Development Action Group. The clients sought to develop premises that provide rental office accommodation and yet demonstrate that the application of green principles in design and construction can become normal in commercial building in the urban environment.

A number of key factors were addressed in the planning and design of the building. One factor of the design approach called for reduced heating and cooling energy consumption in the building, and to this end detailed thermal modelling was used. With passive thermal design being the objective (avoiding the need for air conditioners), the choice of wall materials and construction systems was critical in terms of the features used to optimise thermal performance.

Various construction technologies and materials were considered, including rammed earth, sandbag construction and unfired clay bricks. The final choice was cavity wall construction from recycled concrete brick, sourced locally from Cape Brick.

Concrete masonry is naturally thermally efficient, and when used in cavity wall construction has the effect of creating walling with a high insulation and thermal properties. The walling helps to ensure that the building stays warm in winter and cool in summer, thereby lessening the need for artificial climate control.

Another factor of the design approach called for limiting embodied energy in the construction materials. Embodied energy is the energy consumed in the manufacture and transportation of construction materials to site. To manufacture a masonry product with a low embodied energy the raw materials should be sourced as close as possible to the manufacturing plant and should contain as much recycled material as possible, the manufacturing process should use as little energy as possible, and the manufacturing plant should be as close as possible to the site to reduce the transport energy component.

Cape Brick manufactures concrete masonry units with possibly the lowest embodied energy of any masonry product available in the Western Cape today. This is achieved through both the location of the factory and the manufacturing process itself. Cape Brick, in conjunction with Ross Demolition, is one of the first masonry manufacturers to set up a crushing facility to reduce construction and demolition waste (C&DW) consisting of mainly reinforced concrete, into recycled crushed aggregate (RCA). The RCA is then used as the main ingredient in all the company’s products. In fact, one particular product, the 14MPa concrete plaster brick, consists of 96.5% recycled materials (100% of the non-cementitious materials and 50% of the cementitious materials are recycled). Cape Brick uses approximately 42,000 tons of RCA per year.

Located in Salt River, Cape Brick is only 5kms from the city centre, as well as being the closest major masonry manufacturer to both the Southern Suburbs and the Atlantic Seaboard. This results in shorter distances travelled to site, leading to both cost and energy savings.

The use of RCA also has a hugely beneficial effect on product quality. The quality of the RCA is actually superior to that of the quarried materials available at a similar price. This results in products that are not only more beneficial to the environment, but have a higher compressive strength in the bargain.

The end product is a truly green building material, a recycled brick with a low embodied energy, which itself is fully recyclable. Selected as the product of choice for the Green Building by the leading experts on sustainable energy, Cape Brick’s recycled bricks are also engineering grade, load-bearing, structural concrete masonry units as approved by the Concrete Manufacturers Association. Help to promote sustainable building practice, specify recycled.

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