Clay brick construction – Simply sustainable

Different brick wall types afford greater levels of thermal comfort compared to the lightweight walled alternates in blue. Different brick wall types afford greater levels of thermal comfort compared to the lightweight walled alternates in blue.

THE recent severe weather storms in the USA (the third most active storm season on record) continues to show just why genuine clay brick outperforms other home exterior facades in severe weather conditions – and why South Africans fortunate to be living in “double” skin clay brick homes, have even more to be thankful for than their USA counterparts living in houses with a single skin of face brick as the “exterior” facade. 

Cumulative studies in the USA to compare the performance of different construction types, demonstrate clay brick beats competitive “exteriors” in terms of moisture resistance, earthquake resistance and protection from wind-blown debris. These include:  

The 2010 study by the NAHB Research Centre in the USA, comparing moisture resistance among typical residential exteriors evaluated genuine clay brick veneer (a single outer skin of brickwork) as the highest in moisture resistance and dryness.  Of the eight walling systems tested – these accounting for approximately 90% of the external cladding systems used today in the USA, brick veneer wall assemblies performed the best overall in controlling moisture.

Videos of a 2004 wind-blown debris study at the Wind Science and Engineering Research Centre at Texas Tech University demonstrated that a medium-sized and wind-blown object, such as a 2.2m x 2.4m, would penetrate homes built with lightweight vinyl siding or fiber-cement siding at a speed of just 25mph, but would need to exceed 80mph in order to penetrate the wall of genuine clay brick veneer.  The tests showed that a single wythe (skin) of brickwork exceeded the impact resistance for high velocity hurricanes zones in the Florida building code.

This resilience of clay brick walled houses to withstand harsh weather conditions and natural disaster continues to highlight the value of clay brick walls over lightweight alternates and why those living in clay brick houses have greater peace of mind. 

While an external skin of brick veneer to the exterior walls may set the “highest” performance for system built houses in the USA, South African clay brick homes, as typically designed and built with “double” skin clay brick walls, offer a whole lot more, the two clay brick skins by deduction affording “twice” the structural integrity of their USA external brick veneered counterparts. The demonstrated long-term performance of clay brick also helps explain why South Africans fortunate to have invested in a brick houses, take the integrity of their investment for granted.

Looking to the future and with global warming predicted to make extreme weather patterns even more pronounced, the superior life time performance of clay brick construction brings in to question the very sensibility of the building industry here in South Africa moving towards greater industrialisation for home building.  That an economy as well developed and resourced as the United States has not yet been able to provide industrialised lightweight alternate building systems with assured performance attributes to close the gap with simple clay brick construction that is common place in South Africa, says it all.  

Free of volatile organic compounds, earth friendly genuine clay brick is recognized internationally as a key element of green building design with benefits able to endure way beyond those presented by less durable alternate lightweight building systems.  It was a conclusion of the full Lifecycle Assessments (LCA) by Energetics, which assessed the contribution of different construction types to long-term sustainability that we should build homes able to last beyond 100 years.  Clay brick construction’s proven long term performance points to its unique ability to offer that performance; is widely available and a widely practiced construction method throughout South Africa.

Taking the importance of clay bricks sustainability offering a step further, South Africa’s unique climates characterised by long hot summers and large diurnal temperature swings which are pronounced between the seasons, happen to require the temperature regulating propensity of thermal mass in the building envelope to achieve optimal energy efficiency.  Clay brick provides this important thermal property to naturally moderate internal temperature conditions and facilitate thermal comfort in houses for longer.  This is demonstrated in the findings of the research programme by the Priority Research Centre for Energy at the University of Newcastle, where four purpose-built housing test modules constructed Insulated Brick Veneer Ins-BV, Insulated Cavity Brick Ins-CB, Cavity Brick CB and Insulated Lightweight Ins-LW were empirically measured and assessed.

Key findings of that research as reported on, “Energy efficiency and the environment, the case for Clay Brick, Edition 4 are:

  • The lightweight building was the worst performing in all seasons
  • Brick veneer performs better than lightweight
  • The insulated cavity brick performed the best
  • Thermal mass in floors alone is not sufficient to reduce extremes in temperature

In simplistic terms, and as shown in both the University of Newcastle research and the findings of a modeling study of a 130m² house by WSP Green By Design below, the thermal mass of the clay bricks provide the propensity for clay bricks to function like “thermal batteries”, to slowly absorb and release heat when it is needed most, providing the desired thermal comfort conditions for longer and with that lower artificial heating and cooling interventions. 

The way forward for more energy efficient housing in South Africa however, is not just masonry construction that is already fully compliant with SANS 10400 Building Regulations, but rather taking this well applied proven basic construction methodology to even more energy efficient levels through the application of SANS 204 Energy Efficiency Standards (Deemed to Satisfy) for masonry buildings. This standard defines the combinations of Thermal Capacity ‘C’ and Resistance ‘R’ for the different climatic zones of South Africa. In most cases the inclusion of insulation materials with different R-values between the brick skins offers thermal efficiency enhancements in the winter periods helping keep the heat inside for longer than un-insulated double skin clay brick walls and thereby reducing heating bills.  

For optimal outcomes however (greatest thermal comfort, lowest energy usage at the lowest cost,) the natural propensity of clay brick walling to passively manage and use the sun’s energy to lower the use of energy for artificial heating and cooling is advanced through the application of Passive Solar Design interventions (designing with nature in mind,) involving house orientation to the North in South Africa, ventilation optimisation, correct shading of interior spaces from the summer sun and insulation applied in the building envelope applicable for the climatic zone.  

With industrialised building systems the norm for house construction in many Northern Hemisphere countries it is interesting how research in the USA is validating peoples long term practical experiences here in South Africa to demonstrate clay brick construction superior performance, fortification against natural disasters, and the sensibility that we should hold onto clay brick construction as the common practice for housing in South Africa.  It happens to make a whole lot of economic sense as well given that clay brick houses are provided in South Africa at a lower or competitive built cost and with lower lifecycle costs than comparable alternate lightweight system technology such as Light Steel Frame Building. 

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