Walls have two main impacts on a building's sustainability: firstly they are the biggest component of a building and generally have the most impact environmentally; secondly, most heat lost in a house is through the walls. The materials, their embodied energy, U values and transportation requirements are very important to the sustainability of the overall building.

Breathable walls are also very important as they help to stabilise the moisture content of the internal air, this can improve air quality for people who suffer from breathing related issues and also reduce the amount of bacteria and fungi that relish the highs and lows of realtive humidity. When building breathable structures it is important to note that the internal walls must be more resistant to water vapour than the outer ones. This means that water is constantly being drawn away from the interior. When using lime a good way of achieving this is to use hydraulic lime internal plasters and lime putty external renders.

Blocks made out of recycled materials

These blocks look like and are used in the same way the same as normal blocks. They are made from recycled materials including waste sludge ash from power stations.

Non-fired bricks

Bricks can be made and left to dry naturally. They only use 14% of the energy used to make normal bricks. These bricks are normally used for internal non-load bearing walls. They are breathable, light and provide good thermal insulation.

Recycled / re-used bricks

Bricks that have been used with a lime mortar, rather than cement, can be easily recycled and re-used. This greatly reduces the energy involved in manufacture.

Fired honeycomb clay blocks

These are used widely on the continent and are used to create a single skin wall. They are designed to be naturally insulating, quick to assemble and breathable (see below).


Wood is a very versatile material and can allow us to build cheaply, quickly and efficiently. Timber also has the advantage that it absorbs carbon dioxide from the atmosphere when it is growing. Wood can be used for load bearing walls and for exterior walls. Certain woods, like Oak and Cedar, contain natural preservatives and so do not need treating with chemicals. The flexible nature of timber building means that we can create highly insulated structures.


Straw gives excellent thermal insulations and is easy and quick to build with. It also helps to combat climate change as it is absorbs carbon dioxide from the air as it grows.


Compacted subsoil in the right mixture has been used for millennia for housing and provides an excellent and cheap structure for internal and external walls.


Cob is a mixture of straw and earth that is compacted together by hand. It has been used for years in as a traditional method of building. It provides good insulation but must be made into thick walls (approx. 2 feet thick).

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