Dirk Meyer, Director, Corobrik (Pty) Ltd, South Africa
Clay brick is the cornerstone on which Africa’s bondable built environment is based, thanks to its longevity, structural strength, flexibility in design and application, natural sound proofing qualities, incombustibility and natural resistance to fire, inertness that ensures no release of VOC’s to impinge on the quality of the air one breathes, solidity and security – all wrapped into one neat environmentally friendly package. Added to that, the enduring natural earthy colours and textures of clay face brick walls, that eliminate a life time maintenance costs and associated carbon debt, contribute to a more favorable economic value over the life cycle.
More recently in the context of the international focus on achieving energy efficient houses and reducing energy usage for heating and cooling, comparative empirical and thermal modeling research scientifically demonstrates why clay brick houses are more comfortable to live in, warm in winter, cool in summer and adaptable to all climatic conditions.
Passive solar design interventions involving orientation, shading and ventilation is the common sense approach for addressing operational energy reductions. The use of high thermal mass as provided by clay brick is fundamental, particularly in South African climates, where the primary challenge for walling materials is to moderate the external temperature amplitude to more bearable levels indoors, whilst also ensuring that the average indoor temperatures across all seasons is at an acceptable level for the average person.
Through the power of sophisticated computer modeling, based on years of empirical research data, it has been established beyond question that optimal walling systems should have sufficient levels of thermal capacity (C-value) as provided by the thermal mass of clay bricks and supplemented by appropriate levels of thermal resistance (R-value). Depending on the climatic zone appropriate levels of resistance are provided by the brick itself and the air in the cavity, and in the colder climatic zones characterized by the greater diurnal temperature swings, the incorporation of insulation materials in the cavity between the brick skins.
Thermal capacity “C”, that is so important, acts like a battery in that heat energy is absorbed, stored and released at a later time. In the hot summer months the walls thermal “capacity” slows the transfer of heat from the outside to the inside between 6 to 8 hours, thereby delaying peak indoor temperatures to much later in the day and avoiding the “hotbox” effect associated with alternate insulated lightweight system building technologies such as LSFB and Timber Frame.
In winter, similar dynamics are present, but the focus is more on the ability to absorb heat energy from the low angled winter sun, and then to keep it inside for as long as possible, so as to minimize the need for heating energy. Internal thermal mass holds heat for longer thus providing for longer periods of thermal comfort and lessening the need for artificial heating interventions.
The holistic sustainable value that double skin clay brick walls bring to the built environment is put in context by the findings of the full Life Cycle Assessment [LCA] by Energetics of Australia that assessed the life cycle performance of five different walling systems in a Verdant house type located in three different climatic zones and four different orientations.
