Thermal insulation in the roof system prevents heat flow, thereby creating a comfortable interior.

HomeArticlesThermal insulation in the roof system prevents heat flow, thereby creating a comfortable interior.
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Ceiling insulation aids internal comfort and compliance

The inclusion of thermal insulation in the roof system provides a heat transfer barrier to keep heat in or out as the season demands, and ultimately facilitates compliance with the National Building Regulations (NBR).

The NBR, SANS 10400 XA Energy Efficiency in Building, require significant thermal resistance to prevent heat flow through the roof systems of new buildings and alterations. The aim is to reduce the demand for and use of electrical energy in heating and cooling buildings, by creating a comfortable interior environment.


Insulating in different climates

“There are many options to facilitate compliance with the NBR, including the installation of an insulated ceiling, such as IsoBoard thermal insulation,” says Mark Russell from IsoBoard.

“An insulated ceiling can follow the roof profile if one wants exposed rafters, or it can be installed as a conventional horizontal ceiling. While the choice remains a personal one, from a thermal insulation point of view it is better to have the insulation further away from occupants in warm conditions, but as close as possible in cool conditions, where it is important to reduce the volume of space when heating,” he explains.

So when building a summer holiday cottage or living in a subtropical area, having the insulation following the roof profile is wise if the aim is to keep the home cool. Insulation can be installed either over or between rafters.

If living in cooler climates and in anticipation of having to heat the home frequently in winter, installing insulation as a ceiling will contain heat within the area for longer, and at a lower cost of generation.

One can also install an insulated ceiling board directly below an existing ceiling structure, rather than removing the original ceiling first. “This is a clean and quick way to add the comfort of insulation, as well as repair a damaged ceiling without the mess of removing the original,” says Russell.


How much insulation should one use?

According to Mark, the thermal resistance required by the NBR is very conservative, which means high levels of insulation if one follows the prescriptive table specific to each climatic zone. In certain circumstances it is possible to combine different insulation products, for instance insulated ceiling board and a thermal blanket insulation product, to achieve the required thermal resistance (R-value) at a reduced overall installation cost.

“Following the rational design methodology, one will likely arrive at a required thermal resistance equivalent to a 40mm thickness IsoBoard insulated ceiling, sufficient to maintain a home at a comfortable living temperature throughout the year, with minimum temperature control intervention required,” Russell states.

“An IsoBoard ceiling is paintable and highly water-resistant, so it is perfect for kitchens and bathrooms. It is also safe for use and will last for the lifetime of a building without reducing its design performance,” he adds.