BUILDING: Cape Brick's Better Solution
Recent Western Cape Business News
An immediate but obvious solution to the problem from a design and build point of view is to incorporate energy saving into all new developments. This does not mean only making provision for solar water heating, but in fact runs much deeper. Even the bricks you choose can have a significant impact on the energy used in your development.
There are two aspects to energy saving when it comes to masonry products. The first is to find the product with the lowest embodied energy (the energy required to source the raw materials, manufacture the product and transport it to site), and the second is to use only products that are energy efficient, i.e. that have good thermal resistance and insulation properties.
Although it is a statement of the obvious, it stands to reason that the less the energy required to manufacture something, the less the electricity that will be used. Even if the manufacturing equipment is diesel driven, the production process for the fuel itself still requires electricity usage. Products manufactured by businesses that use a waste source as a raw material stream, that are located close to their raw material supply, that have a low energy manufacturing process and that are located close to the market will have a low embodied energy product.
Cape Brick, located in Salt River, Cape Town, manufactures bricks and blocks, as well as decking and retaining wall blocks, using almost exclusively recycled aggregate. This is aggregate that has been sourced by crushing, grading and sieving construction and demolition waste, mainly reinforced concrete from building demolition.
“The use of recycled materials is crucial to achieving a low embodied energy product, and Cape Brick’s products have the lowest embodied energy of any conventional masonry product available to the market, by quite some margin. The average embodied energy value determined for their product range is 0.50mJ/kg. (All their products contain a minimum of 80% recycled material, but their plaster stock brick is even better at 96% recycled material). This product also has the lowest value for carbon emissions,” says Cape Brick’s Jean Tresfon.
“Of course these results indicate the energy content from the cradle to the factory gate. When the transport energy to site is considered as it must be, then again Cape Brick scores the lowest on the embodied energy score, being located only 5kms from the Cape Town city center,” Tresfon says.
Before Cape Brick started using recycled crushed aggregate and used regular virgin aggregates like most other manufacturers, their stock bricks had an embodied energy value of 0.86mJ/kg, which is still lower than most manufacturers’ current values. The change to recycled materials and the resultant lowering of the embodied energy translates to an energy saving of 3,625,505mJ per month. This equates to 1 007 085 kWh or the equivalent of running 2000 medium income houses per month, according to Tresfon.
“Of course the other spoke in the wheel of energy saving must also be considered, and this is the energy efficiency of the masonry product.”
“The main requirement of any masonry product in terms of energy efficiency is that the product should have good thermal insulation and resistance properties. The energy efficiency of any walling material is determined by how it handles heat, how heat transfers through it and how well it holds or stores heat. Remember that heat always moves from warm to cold, so in summer with the outside temperature warmer than the inside, the heat transfers through the walls from the outside in and vice versa in winter.”
“Concrete masonry is naturally thermally efficient and when used in conjunction with cavity wall construction it has the effect of ensuring that buildings stay warm in winter and cool in summer, thereby lessening the need for artificial climate control and wasted energy.”
“The secret of concrete block’s energy efficiency is in its mass. The thermal mass of concrete slows down the passage of heat moving through the wall and allows a masonry structure to absorb heat, instead of passing it through to the inside of the building. As the wall is cooled by shade or nightfall, the absorbed heat is then released back to the outside, keeping the inside cool. Likewise, this thermal barrier helps keep a concrete masonry structure warmer during the winter months,” according to Tresfon.
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