Walls & Roofs Magazine speaks to industry experts about new developments, insights and opinions regarding insulation solutions in South Africa.
In South Africa, the tendency in building properties leans towards the low capital cost side and not energy-efficiency. A shift in mindset is needed against the backdrop of the price of electricity, as well as to ensure the comfort of clients and building occupants.
In a report entitled “Back to the drawing board: Insulation in buildings” by the national power utility, Eskom, the importance of insulation is discussed.
“Insulation in the building envelope is one of the most important factors for improving energy-efficiency in buildings. Insulation curbs the natural flow of warm air towards cooler spaces, limiting heat loss from the inside and heat gains from the outside. An insulated room requires 51% less energy to heat up a room than one that isn’t,” says Eskom.
Materials used in the manufacture of thermal insulation products:
• Synthetic polymers (polyester, polystyrene, polyurethane, polyisocyanurate).
• Mineral wools (fibre-glass, rock wool, slag wool, stone wool).
• Minerals (Vermiculite, Perlite).
• Natural plant materials (cellulose insulation, cork, hemp, cotton, straw, sawdust and hemlock fibre).
• Animal fibres (wool).
• Shredded recycled paper chemically treated – cellulose loose-fill insulation).
Des Schnetler, the chairlady of the Thermal Insulation Association of Southern Africa (TIASA), says that there’s still a tendency in building properties to lean towards the low capital cost side and not energy efficiency.
“Unfortunately people settle for the cheapest option without taking quality into account. This results in under performance with regards to the thermal efficacy of insulation products and even the usage of unsafe products which are not tested for fire performance – this puts the safety of occupants at risk and it also endangers the property itself,” says Schnetler before adding that building professionals and specifiers need to specify products that has been tested by the SABS and are in compliance with the relevant product standard or has the SABS Mark of Approval. The product standard normally includes attributes such as fire performance, durability as well as thermal efficiency.
“The SABS product standard ensures that the products used in buildings are safe in the event of a fire and are in compliance with the Application of the National Building Regulations SANS 10400-T,” adds Schnetler.
“When your house has a lower energy demand due to proper insulation, off-grid energy becomes more viable,” says Llewellyn van Wyk, principal researcher in sustainable building at the Council for Scientific and Industrial Research (CSIR). “And to the extent this happens, to the same extent your net-zero becomes achievable,” adds Van Wyk, before explaining that net-zero energy in the United States (US) is almost commonplace now, because so many people are doing it.
The US (and other countries in cooler climates) is at an advantage, however, seeing as it’s easier to remove cold than it is to remove heat in a building.
“The heating is a bit more difficult than the cooling. In cold climates it is so much easier because you can run hot water systems with radiators and under-floor heating,” says Van Wyk.
South Africa, however, isn’t that cold and the climate is going to become even hotter in future years, so getting rid of the heat in a home is the challenge that we need to focus on. Van Wyk says the building and insulation technologies are getting to a point where service neutrality across the board is becoming more of an option.
This is why, says Van Wyk, building material choices are becoming increasingly important. “Some materials will simply never provide the insulation performance that we need in order to create cool building environments. You can, however, make the building perform better – this is why your choice of window, ceiling and roofing products is critical,” says Van Wyk.
“Heat loss is a greater problem as the majority of conventional houses in South Africa leak the most in winter and the temperature difference between indoors and outdoors, is at its greatest,” agrees Schnetler.
“In the past, no one thought much about insulation. Energy was abundant and cheap. With the introduction of the Energy Efficiency Regulations and Standards in August 2011, to intervene and to reduce peak electricity demand usage, thermal insulation is now mandatory in certain building occupancy classes and it will play an integral part in the future design of a building,” comments Schnetler.
Levelling out the climate curves in South Africa
Another challenge is the fact that the winter/summer and day/night temperatures in the country can be extreme, even in the same city. “There are extreme temperature curves. In a city like Pretoria, for example, you’ve got a 40 degree temperature curve between seasonal as well as day and night temperatures. So the question is: Can we create a building envelope that levels out this curve?” asks Van Wyk.
While it’s not yet possible to completely even out the temperature curves, great strides are being made. “What we are trying to do, is get a -5°C environment to about 16°C and a 35°C environment to 22°C with proper insulation in order to ensure a year-round comfortable space and flatten this curve. Indoor comfort levels are between 18°C to 24°C, so the closer we can get to this, the better,” adds Van Wyk.
The CSIR is currently experimenting with building envelopes that are able to flatten this temperature curve so that less energy is needed to heat or cool a building. “We’ve almost achieved this in the house that we have built here at the CSIR. It doesn’t require heating – in winter if you put the kettle on or take a bath/shower and do your cooking, there is enough heat,” comments Van Wyk.
What SA can learn from countries in cooler climates
In a presentation entitled “Energy efficiency in buildings: Lessons learnt from Germany and thoughts on South Africa”, international advisor of energy efficiency at the South African National Energy Institute (SANEDI) and the Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ), Christian Borchard, discussed a number of issues pertaining to insulation and sustainability.
While South Africa and Germany have opposite climates, there are many things that we as a country can learn from how they manage extreme temperatures.
In 2009, coal contributed to South Africa’s primary energy consumption by 70%. In Germany, only 24% of the country’s electricity came from coal in 2009. However, it is not only on the source of energy, but how much of this and how efficient it is being used to heat and cool buildings in the respective countries.
“In Germany, 78% of household electricity is attributed to heating, while this is only 16% in South Africa. In South Africa, 39% of household electricity consumption goes to heating water through a geyser, while hot water only accounts for 9% in Germany,” said Borchard.
South Africa has a much smaller heating demand but at the same time a higher cooling demand than Germany. Building materials that better insulate in order to keep the desired heat or cold temperature in the building could be help to reduce the energy demand.
Insulation effect of materials often unknown
“Did you know that 20mm of insulation has the same effect as 1050mm of concrete?” asks Borchard, before explaining the insulation effects of different materials compared to a 20mm insulation board.
“Only 20mm of insulation has the same insulation effect as 900mm of ordinary bricks, 290mm of hollow bricks, 235mm of clay straw, 80mm of perforated brick, 65mm of timber or 60mm of lightweight concrete. As anyone can see, some thinking of the insulation effects of different materials is crucial in the design of a sustainable building” says Borchard.
Fig. Insulation effects of different materials, Source: Energy Agency NRW
“Insulation thickness in SA does not need to be excessive, but some insulation should be mandatory in attics and it should be considered more often when traditional bricks and concrete are being used and the building will be heated or cooled by HVAC” adds Borchard.
“Bricks have been a common regional construction material in South Africa and are still produced locally. New developments see high-tech perforated bricks with U-values as low as 0.2. I believe that perforated brick development is a huge opportunity in South Africa – both in terms of job creation as well as energy efficiency. In addition this product could easily be manufactured locally,” says Borchard.
Single-glazed windows represent probably more than 98% of local window installations in South Africa, even though the insulation benefits of double-glazed (as well as other, higher performing solutions) have been internationally acknowledged for many years now.
“Double glazing and thermally separated window profiles can make tremendous improvements in reducing heating and cooling losses in your building,” concludes Borchard.
Understanding local climate conditions
According to the Clay Brick Association of South Africa, to achieve optimal thermal comfort without mechanical heating and cooling begins with understanding the local climatic conditions in which the building is built and the fundamentals of how your choice of building materials will perform.
Thermal mass is an important thermal performance property for achieving optimal thermal efficiency since it provides walls with the ability to self-regulate, to slowly absorb and store heat and then release the heat back into the cooler night air, attenuating the high and low points of the temperature curve more within the18°C to 24°C comfort zone. This function is particularly important for climates such as South Africa, which are characterised by well-defined diurnal temperature swings across its climatic zones and long, hot summer days.
At the end of the day, thermal control within buildings can’t be the sole responsibility of designers and builders (although we have a large role to play). Mandatory codes and standards, including government building energy codes and equipment standards, voluntary programmes as well as policies and incentives, are needed. Not only does this ensure buy-in from clients, but it will help to educate end-users on how they will benefit from a properly insulated space in the long run.
The key principles of energy-smart design include:
• Design for climate.
• Appropriate siting.
• Internal planning to create zones which reduce the amount of energy required for heating and cooling.
• Windows that are appropriately orientated and sized with protection from winter heat loss and summer heat gain.
• Adequate thermal mass (building materials) to stabilise indoor temperatures.
• Adequate thermal insulation in roofs, ceilings, walls and floors.
• Good draught proofing.
• Cross-ventilation for summer cooling.
• An efficient hot water system and fittings, located close to use station.
For more information, visit www.claybrick.org, www.eskom.co.za, www.csir.co.za; www.giz.de and www.tiasa.org.za to which full thanks and acknowledgement are given.