Thermal Insulation Technology – How Radiant Barrier Insulation Will Influence Building Design

Johannesburg: Africa Thermal Insulations (ATI), specialists in developing thermal insulation products that meet recently updated building regulations required for proof of compliance and occupancy certificates, acknowledge the need to educate building professionals and consumers regarding the correct use of reflective foil materials.

Architects and building developers wanting to ensure that they stay compliant with recent building regulations, increasingly acknowledge the importance of calculating the energy expected from the buildings that they design and develop.

In 2005, an important initiative by the Department of Minerals and Energy at an energy efficiency strategy gathering, resulted in SANS204 being made mandatory in National Building Regulations. SANS204 essentially refers to the environmental sustainability and energy usage of a building. Many of the standards that were passed with this new regulation were based on the Australian BCA and essentially call for Commercial and Public Buildings to meet the target of a 15% reduction of Final Energy Demand.  

In South Africa, the incorporation of outdoor elements has a heavy influence on building design. This in turn requires architects to carefully balance the need to create comfortable living and work spaces with regulations that limit the energy usage of a building, for example SANS204 stipulates that the annual consumption of an office in Gauteng shall not exceed 80 VA/m² and 200 kWh/(m²•a). An important element for architects and building developers here is their understanding of how the thermal resistance (R-value) of insulation and roofing products is going to impact on the design of a building.

When SANS204 was promulgated typical products such as Polyester Fibres, Fibre Glass and Boards were naturally considered because of their existing presence in the market, with their thickness contributing greatly to the necessary R-values that SANS204 recommends. New technologies such as radiant barrier products have taken a long time to break into the market, mostly because of a lack of understanding as well as awareness of the important role that they can play in insulating the roof cavity of a building. The fact that when SANS204 was published with very little elaboration of how reflective foils and radiant barrier insulation could influence R-values also didn’t help in making professionals aware of the potential of these products.

Reflecting on the R-Value of a Roofing System

Because SANS204 was published without sufficient analysis and explanation of radiant barriers, the Thermal Insulation Association of South Africa (TIASA) commissioned Alf Peyper, a consulting member, to write a technical guide for the industry. The resulting work, “The Guide to Radiant Barrier Insulation”, has subsequently been released and has been endorsed by ESKOM. In this guide, SANS10400-XA: Energy Usage in Buildings is discussed, Fundamental Principles of Radiant Barriers and Reflective Foils are explained and the effects of Mean Temperature Change on Conductance and Resistance are clarified. Insulation Types and the Calculations of Heat Flow are also discussed.

 

Understanding that the R-value, or thermal resistance, is the measurement of resistance to the flow of conductive heat transfer is fundamental to knowing how the selection of appropriate roofing products will help towards meeting SANS204 requirements. The objective of the guide released by TIASA is to clearly lay out the principles and calculations that building professionals need to be aware of when understanding how radiant barrier and reflective foil products can contribute to achieving the energy efficiency requirements of SANS204.

Adequate information is provided so that architects, specifiers and builders can get a clear understanding of how to:
•    Determine the Total R-Value of an average roof system
•    Make buildings more energy efficient and reduce their environmental impact
•    Comply with the requirements of SANS 10400-XA Energy Usage in buildings
•    Build with accepted industry installation practices
•    Clarify and standardise the value of reflective foil insulation in typical building applications.

In addition to understanding how SANS204 expects the R-value of a product to be considered in the design of a building, it also identifies four climatic zones that will require a tile underlay with a radiant barrier. Radiant barriers contribute towards the suggested R-values, tile underlays do not. Essentially, this is to ensure that in climatic zones with high summer temperatures buildings will need to include materials that reduce heat transfer through radiation. Because the temperature of the roof cavity of a building will inevitably be transferred to the living and working space, those responsible for designing and developing buildings will in future need to ensure that the roof of the buildings they design incorporate an element of heat resistance and therefore reduce the energy required to maintain a comfortable temperature.

Acknowledging the Effectiveness of Radiant Barrier Insulation

All white or light coloured and highly reflective surfaces will reflect a major proportion of heat away from a building when newly installed. This is where products selected and installed as a radiant barrier insulation system really performs at its best. The bottom surface of the foil facing the open air gap will emit 3 – 5% of the heat, keeping the roof cavity cooler without using energy. The ability to emit or radiate heat out is the real work which is performed by reflective foil insulation products and greatly contributes to the quantities of bulk insulation that may be required. ATI’s signature product – Alububble® – a radiant heat barrier insulation solution that has been endorsed by the Thermal Insulation Association of Southern Africa, is designed to provide a stable roof temperature allowing any bulk insulations that are a part of the installation to work more effectively by minimising the heat load.

Warren McNey, Managing Director of ATI, and a member on TIASA’s Technical Committee, confirms that “there is no choice for architects and building developers but to accept that the buildings of the future will need to incorporate roofing and insulation materials that contribute to the reduction of the transfer of heat due to radiation. That understanding how the R-value of materials is going to influence how buildings are designed and the energy they require will be significant in years to come”.

Contact details for editors and readers:
Nolene van den Heever: Div Sales Director
nolene@ati-insulations.co.za
Tel: +27 11 462 9122