Principles of Insulation

The Concept of Heat Transfer

The core purpose of insulation is two-fold. It must reduce heat transfer in order to keep the building cool in summer and warm in winter.

Heat flows naturally from a warmer to a cooler space. In winter the warm air from inside the building escapes outdoors and in summer hot air from outside infiltrates the interior of the building.

Heat Transfer takes place in three ways

Radiation - from surface to surface through an air space.
The movement of heat away from an object by means of electromagnetic waves (infrared rays) is known as radiation. This process does not involve any molecules other than the substance...

The fundamental principles of radiant heat barrier / reflective foil

Reflective insulation materials work on a different concept than conventional bulk insulation like rigid foam boards or fibrous blankets. Unlike conventional bulk insulation, reflective insulation has very low emittance values "e-values" (typically 0.03, compared to 0.90 for most insulation) and that significantly reduces heat transfer by radiation.

In order to understand reflective insulation capabilities, one must be aware that the radiant heat rays of the sun do not become heat until they strike an object such as a home or everything that is in it. Thus, radiant heat rays must be kept out in warm weather; while in the cold weather, warmth must be kept in...

Sisalation® reflective foil radiant heat barrier

Sisalation® significantly resists radiant heat flow due to its reflectivity, low radiant heat absorption and low emissivity (ability to re-radiate heat).

Installed in conjunction with an airspace Sisalation's® shiny foil surface is an excellent reflector of all long wave, radiant heat that strikes it – as much as 95% of radiant heat is kept out. Additionally, it is a poor re-radiator of heat. Should it be heated or come into close or physical contact with a warm surface, it will only re-radiate about 5% of the heat, compared with approximately 90% that ordinary surfaces would radiate at the same temperature.

Sisalation® aluminium foil insulation is manufactured according to ISO 9002 quality systems and is a SABS approved product. It has two firsts behind its name – first to be awarded the SABS mark...