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Rendering is a method of protecting a building from the weather as well as providing insulation for a building.
Rendering has been used for hundreds of years in construction with traditional lime based render used to protect poorer quality rubble walls in Tudor times.
Whilst not as common in the UK as in other nations such as the US, various rendering techniques are making a comeback as not only do they provide decoration, an external wall rendered properly can drastically reduce the heat loss from a building.
Lime renders were traditionally applied to give protection to walls built of poor quality rubble, stone, or porous brick, or to walls in exposed locations facing driving winds.
Render works by acting as a sponge, absorbing rainfall, then allowing it to evaporate, rather than soak into the wall.
Rendering the external walls of a building requires new material to be placed over the existing wall. This can be made from many materials and is usually between 50mm and 100mm thick.
It is estimated that using insulation of this thickness can reduce emissions from a three bedroom houses carbon by 2.6 tonnes of CO2 a year, which works out as a saving of around £300 on heating bills.
The different types of materials used in rendering allow a green builder to make the best choice based on a number of factors such as cost, environmental impact, decoration and durability.
Lime based render is one of the oldest methods of rendering. Limestone is heated and once the carbon dioxide contained within is burned off it is added to water to create a putty.
This putty then has aggregates such as sand added to it and is placed onto the wall. Whilst lime rendering is a natural process, it also requires a lot of energy to create.
The heating of lime not only releases CO2 from the lime, but also creates CO2 through the act of burning materials to reach the 1,200 degrees Celsius required to burn off the CO2 within the lime. This reduces lime renders environmental credentials immensely.
Rendering provides a vital function on any building providing insulation and weather proofing. Where solid external walls are used it can increase the insulation of a building greatly allowing savings of nearly 2.4 tonnes to be made on CO2 emissions and £300 a year annually on heating bills.
Rendering also allows the external look of a building to be customised and protected preventing excess moisture from penetrating into a structure.