Thermal insulation is the material used to reduce the rate of heat transfer through external surfaces in the home or building. Basically, when you insulate your building you are wrapping it in a “protective blanket”, which reduces the transfer of heat into and out of the building.
In winter it reduces the rate at which heat is lost from the building, and in summer it reduces the rate of heat entry into the building. For example, in an un-insulated building on a hot day, heat is conducted easily through your roof, windows and walls from outside, raising the temperature inside.
Insulation by its very nature saves energy. Each type of insulation has its own advantages and disadvantages. Our advice would be to choose the product best suited for each application.
The level or performance of an insulation product is measured by its thermal resistance or “R-value”. This is a measurement of the insulation’s resistance to heat transfer and is expressed as a number normally between one and three. The greater the “R-value”, the more effective the insulation at resisting conducted heat flow into the building in summer and out of it in winter.
Therefore, the “R-value” is actually a measure of performance. One brand of insulation may be thicker or thinner than another, but if they both show the same “R-value”, they will perform equally.
The recommendations for the correct “R-value” are based on the climatic conditions in particular locations. The deemed-to-satisfy provisions are based on climate zones, including dry bulb temperatures, thermal neutrality, humidity and southern coastal condensation risk (see map of climatic zones of South Africa). Please check the map for details of your area. These values are recommended in SANS 10400-XA Energy usage in buildings and SANS 204 Energy efficiency in buildings.
There are two basic types of insulation:
Some insulation products also use a combination of bulk insulation and reflective foil to achieve their insulating effect; this is known as composite bulk insulation.
This is the type of insulation that most people are familiar with. The insulation material itself is usually fibreglass, mineral wool (also called rock wool) or synthetic fibre (polyester). These products come in two forms, either in rolls, called blankets, which must be cut to fit the length of space or in precut lengths, called batts. In a horizontal space like a roof space, blankets or batts are simply laid between the timber joists.
Loose fill (cellulose fibre) insulation is supplied loose and is simply poured or pumped into the roof space or cavity walls. Cellulose fibre is made from recycled paper which has been chemically treated to resist fire, rot and vermin.
Rigid bulk insulation comes in pre-cut boards. They are also ideal for insulating areas such as raked ceilings, solid brick external walls, under wooden floors and concrete slabs. Extruded and expanded polystyrene boards are most commonly used because of their rigidity and strength.
Reflective foil insulation has an ability to minimise radiant heat transfer. It can also act as a water proofing membrane under a roof and as a moisture barrier in roofs and walls. When using single layer reflective foil under a tiled or metal roof, bulk insulation may still be needed at the ceiling level to achieve a good level of insulation through all seasons.
Flat ceilings with pitched roofs are the easiest to insulate. Bulk insulation should be installed allowing batts and blankets to expand to their natural thickness, cut neatly to fit snugly between ceiling joists, and kept clear of recessed light fittings. Blow in insulation should be sprayed with a solution that prevents disturbance from breezes within the ceiling spaces.
Important notice!! The presence of electrical fittings and wiring may necessitate a reduction or removal of insulation in some areas. For example, do not put insulation over or around recessed light fittings like down lights mounted in the ceiling and transformers – leave a 25 mm gap around their perimeters free of insulation to allow heat generated by the light fitting to dissipate
Use reflective foil laminate over the rafters but below the battens of the roof tiles with a minimum overlap of 150 mm.
The quality of the workmanship to install the insulation is critical for residential and commercial buildings to be energy efficient. We have established a “Specialized Contractors Division” within TIPSASA to push to improve the installation quality as it gets far less scrutiny than plumbing or electrical work. The best insulation could be ruined if incorrectly installed.
With the various products on the market today, all claiming to be ‘green,’ how does one choose the best product to complement a sustainable approach to building? To some it is recycled content and to others it is the use of renewable materials then again others believe that it is products that do not contain certain raw materials, there are many definitions and interpretations.
Warning: Extravagant marketing claims – Buyers beware
It is common to see ads claiming that certain insulations are ‘fire-proof’ or ‘rodent-proof.’ Request proof of test results to substantiate these claims. Be wary of companies over promising their products’ abilities. The old adage, ‘If it sounds too good to be true, it probably is,’ definitely applies here.