The needs of today's society differ greatly from those of only a few years ago. Growing concern about resource depletion and degradation of the environment dominates the world's agenda and there is an increasing demand for sustainable and energy efficient building materials.

There are two requirements to an energy efficient masonry product. The first is that the product should have good thermal insulation 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.

The second requirement to an energy efficient masonry product is that it should have a low embodied energy.

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. The use of recycled aggregates is crucial to lowering the embodied energy of masonry products.

Cape Brick,located in Salt River, now manufactures concrete masonry units with possibly the lowest embodied energy of any masonry product available in the Western Cape today. 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, to recycled crushed aggregate (RCA). The RCA is then used as the main ingredient in all the company's products. In fact, our 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.

From manufacture to transport to construction, concrete masonry is modest in its energy needs and generous in its payback. No change in construction technique is required by specifying this truly green building product and it is also cost effective, meaning that not only will you help to promote sustainable building practice, but will realise a saving in the process.

For further information please contact Jean Tresfon at (021) 511-2006.