Radiant barrier insulation reduces heat build-up


The newly legislated SANS 10400-XA: 2011 and SANS 204: 2008 introduce the requirement for proof of compliance with the standards set out for energy efficiency in buildings. This means that architects and building developers need to ensure that new buildings and building refurbishments are designed to meet the prescribed energy efficiency standards; that a building’s performance in terms of energy usage is calculated and documented; and that the building is built to perform accordingly.

Thermal insulation materials – for roofs, walls and floors – constitute a key element in building to achieve the required thermal resistance values (R-values) as set out in SANS 204.

Africa Thermal Insulations (ATI), specialist in the development and manufacture of thermal insulation materials, highlights that when SANS 204 was developed, radiant heat barrier insulation and reflective foil insulation materials were not well established. SANS 204 therefore focuses on bulk insulation materials – such as polyester fibre, fibreglass and insulation boards – and their contribution to overall heat resistance measures in the different building components. However, ATI emphasises that reflective foils and radiant barrier insulation can play an important role in achieving the required R-values in roofing systems.

Because SANS204 was published without sufficient analysis and explanation of radiant barriers, the Thermal Insulation Association of South Africa (TIASA) commissioned a technical guide for the industry. TIASA’s Guide to Radiant Barrier Insulation has subsequently been released and has been endorsed by Eskom. The guide looks at SANS10400-XA: Energy Usage in Buildings; it explains the fundamental principles of radiant barriers and reflective foils; it explains the effects of mean temperature change on conductance and resistance; and it presents various types of insulation and calculations of heat flow. It provides architects, specifiers and builders with the information they need to determine the total R-value of a roof system and to ensure it complies with the requirements of SANS 10400-XA and SANS 204.

The guide also identifies four climatic zones (within the six climatic zones defined in SANS 204) where tiled roofs will require a tile underlay with a radiant barrier – because the radiant barrier will contribute to meeting the stipulated R-values whereas a standard tile underlay will not. Essentially, this applies in climatic zones with high summer temperatures where building materials need to reduce the extent of heat transfer through radiation – in turn to reduce the energy required to maintain comfortable indoor temperatures.

All white or light-coloured and highly reflective surfaces will reflect a major proportion of heat away from a building when newly installed. According to ATI, this is where radiant barrier insulation systems perform best. The bottom surface of the foil will emit 3% to 5% of the heat, keeping the roof cavity cooler without using energy. The material’s ability to emit or radiate heat out also affects the quantity of bulk insulation that may be required.

ATI’s signature product – Alububble® – a radiant heat barrier insulation material that has been endorsed by TIASA, is designed to provide a stable roof temperature and it enables any bulk insulation that is part of the installation to work more effectively.

Warren McNey, managing director of ATI and a member of TIASA’s Technical Committee, says that going forward, “Architects and building developers, as well as roofing specialists and suppliers of insulation materials, will need to understand how roofing systems, including insulation materials, can contribute to reducing the transfer of heat due to radiation. The R-value of materials is going to influence how buildings are designed for years to come,” he says.


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