Sustainable Home Design — Insulation

Sustainable Home Design - Insulation


Even if you are insulating post building, you can do a lot – the main things being roof insulation, geyser and geyser pipe insulation (see Geysers). Then things get more expensive – for example replacing all your windows with double glazing and low E windows, and retrofitting insulation into your walls, floor etc. In the further reading section below there is a link to the Thermal Insulation Association of South Africa site which has good information on designs and materials. If you are building from scratch, you can design your walls, floors etc to be insulated very easily at low cost.

The Thermal Insulation Association of South Africa (see Further Reading below) has detailed information on designs and materials. If you contact them, they will get back to you with what materials are best for your region of South Africa.

As an example, this was supplied with reference to query about insulation for Cape Town:

The single most important measure to make your house energy efficient is the addition of insulation to the walls and ceilings (minimum levels of insulation will become mandatory through the energy rating legislation in 2007/2008). Insulation is the material that slows down heat transfer through the external surfaces of your home. It can make your home up to 10°C cooler in summer and 5°C warmer in winter.

In an un-insulated house approx. 40% of heat loss takes place through the roof and ceiling, whilst around 35% of heat is lost through walls and floors. The performance of bulk insulation materials is specified with an R-value. The greater the R-value, the more effective is the insulation at resisting conducted heat flow into your house in summer, and out of it in winter.

For the Cape Region, the recommendation is an R-Value of 3.2 for the roof and an R-Value of 1.7 for the walls. Note that reflective foil type products do not have an R-value, but are very effective in minimising heat transfer. They do need to have an associated air gap next to them for them to work effectively.

Blanket and Batt Insulation — There is a range of bulk insulation materials which come in two forms, either in long rolls (called blankets) which must be cut to fit the length of space, or in pre-cut lengths (called batts). This is installed on top of the ceiling.


  • 100mm Aerolite (fibre glass) supplied by Owens Corning – Contact Number 021-951 1167
  • 100mm Isotherm (polyester fibre)supplied by Brits Textiles – Contact Number 021-577 1490

Loose fill insulation — has no backing and is supplied loose. It is simply poured or pumped into a wall cavity or roof space


  • 100mm Thermguard supplied by Thermguard (Pty) Ltd – Contact Number 021-557 4201

Rigid insulation — comes in pre-cut boards that are used primarily in new home construction and are ideal for insulating areas such as raked ceilings, solid brick external walls, under wooden floors and around concrete slabs.


  • 85mm Isoboard (rigid extruded polystyrene board) supplied by Isofoam (Pty) Ltd – Contact Number 021-930 5074
  • Sustainable Home Design - Insulation
  • 10mm Kulite (rigid expanded polystyrene board) supplied by Sagex – Contact Number 021-951 1167
  • 10mm Isolite (rigid expanded polystyrene board) supplied by Isolite – Contact Number 021-951 6100

Reflective foil insulation — works by reflecting large amounts of heat from its reflective aluminium surface, and transmitting very little heat due to the emissivity of the product. Due to these characteristics it is more effective in summer than winter.

For more personal assistance we recommend you contact Mr Thomas Datel at Datel Consulting/Datlink Insulation – Contact Number 021-8641634.

Should you require any further information or assistance please do not hesitate to contact us.

Yours sincerely

Desiree Schnetler TIASA Marketing Chairperson in the US) also have some of the highest insulation properties of any insulation material and are well respected from an environmental footprint perspective.

The main pipes that can be insulated after a house has been built are the geyser pipes leading from the geyser into the wall. Most hardware stores in South Africa sell pipe insulation for these. If you are building from scratch, you could insulate the pipes throughout the house, including within the walls.

See Geyser Blankets in the Geyser section

There are several factors to take into account with glazing:

  • The first is that you want to stop the summer sun from hitting windows and heating up the air behind them, but allow the winter sun in. To do this you either need to provide enough shade to keep the summer sun off, but not to much to allow the lower winter sun in (see Passive Heat Control), or you need windows with a special coating to keep the sun out. The problem with the later is that you might keep to much of the winter sun out, depending on the material.
  • The second is that you want to keep the winter warmth generated via the glass in the house. To do this you either need double glazing (or double with a special gas in between the sheets, or even triple glazing in some extreme climates), or another coating on the glass to keep warmth in (actually works differently to keeping the sun out in the first place).

PG SMARTGLASS provides products both solutions, and various suppliers also supplly double glazing. Wood is preferable to aluminium or PVC as it’s a better insulator and is a renewable resource with a far lower environmental footprint in it’s production). However replacing all door and window frames in a building in order to retrofit double glazing is extreme, so Smartglass might make more sense for retrofitting.

Double Glazing: – although US only, this is a very interesting low cost double glazing solution (in fact some people put clingwrap or bubblewrap on windows in winter to keep the cold out, which is an extremely low cost solution, but of course not particularly good looking).

Insulation options in SA are very limited – looking at overseas designs, even where blow in insulation is used in a roof, they also still use other materials specially designed to combat moisture and air flow. (this opens a PDF within the browser – make sure you also click on Technical Information on the left of the web page)

  • The Good House Book. pg 70 onwards

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