Improve Energy Efficiency for Buildings By Using Wooden Windows

The energy efficienty ratings for wooden windows are better than those for metal or PVC

~ Energy efficiency in South Africa

~It is generally accepted that the majority of houses in South Africa are energy inefficient as they are not designed or constructed to maximize energy efficiency. It is recognized by the government that we need to become an energy aware society. To this end legislation is being planned to encourage architects and builders to consider energy efficiency in their designs in future.

Building regulations in South Africa are under review with the need to reduce energy demand from industry by 15% in 2015. Standards South Africa has been working on two performance standards SANS 283 and 204 in which standards are being prescribed for all naturally and mechanically ventilated buildings. Energy efficient windows are a particular focus so that contractors and homeowners will have a guide for the planning and design of their development.

The Australian building code has been used as an example because their standards relate to similar climatic conditions that we find in South Africa.

South Africa has been divided into six energy usage zones dependant upon climatic conditions. They are described as

1. Cold Interior

2. Temperate Interior

3. Hot Interior

4. Temperate Coastal

5. Sub-Tropical Coastal

6. Arid Interior.

Energy performance ratings for windows have been established for climatic conditions in numerous countries including USA, most European countries and Australasia. A Label is affixed to a product to indicate the energy efficency ratings

The main factors for which ratings have been decided in these countries are:

1.The U-factor. Expressed as U-value. The rate at which heat is lost from a building. The lower the value the better.

2.The R-value. This relates to how well the window insulates the building and restricts heat transfer. The higher the value the more effective the insulation in resisting heat flow into the building in summer and out of it in winter.

3.SHGC. Solar heat gain co-efficient This indicates how well a product blocks heat from the sun. The lower the number the better. A low SHGC means the window transmits less solar heat.

4.Visible transmittance refers to visible light being transmitted. The higher the VT, the more light is transmitted.

5.Air leakage. Heat loss and gain occur by infiltration of air through the cracks in the window assembly. The lower the AL the better.

6. Condensation resistance. This measures the ability of a product to resist the formation of condensation on the interior surface of that product

For more information on energy performance ratings go to www.nfrc.org

~ Energy efficiency ratings are country specific

~It is important that the above ratings are country specific and so a facility is being built to test South African products and determine the co-efficients for South African climatic conditions and the six energy usage zones. It should be ready early in 2007.

~ Timber Windows Performance Ratings

~The ratings for timber windows internationally are better than those for metal or PVC windows and are recommended by the WWF as timber windows require less energy, are more efficient and less CO2 is emitted into the atmosphere in their production.

Energy Efficient Building Design Principles

1. Design for climate – per the energy usage zones and climatic conditions

2. Insulate walls, ceilings, windows and doors – increase insulation levels

3. Consider building orientation – main living area windows to the north (if in the southern hemisphere)

4. Position windows to allow cross breezes to ventilate rooms naturally.

5. A light coloured roof reduces the flow of heat from solar radiation better than a dark roof

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