INTERNAL WALLS

The internal walls of a building often do not support any load. This allows for a greater range of materials to be used with design and sound insulation becoming more important than overall strength.

Timber stud walls are entirely of timber simply nailed together, with only the head and sole plate being screwed or nailed to the ceiling and floor.

The studs (verticals) need to be accurately cut to length, and horizontal noggins need to be fitted between studs for rigidity and for the fixing of heavy wall mounted items such as basins or cupboards. Where services like water pipes or electric cables need to be run inside the framework, the studs must be drilled out to accommodate them.

When using timber in any way it is essential to first try to source recycled timber and if none is available always ensure it comes from a sustainable forest ideally one that has been FSC certified. Insulation can be added to a timber stud wall. However care should be taken when choosing which type, whilst foams are more effective, they create problems in disposal. Ideally natural wool should be used providing thermal and acoustic insulation.

Earth based internal walls can be constructed by using a fine wire mesh. Clay plaster with a higher aggregate mixture than normal can then be placed onto the mesh and, when dry, will form a breathable durable wall.

Plasterboard walls, or dry walls, as they are sometimes known consist of a core of gypsum plaster wrapped in a liner of paper. Dry walls are supplied in panel lengths and as such cannot be made on site. This means that they will require transportation, which will add to the carbon footprint of the build.

Dry wall manufacture is also a very heat intensive process with over 25% of the total cost of a dry wall going on natural gas used in its construction. Dry walls cut to size often lead to a large amount of offcuts.

These cannot be disposed of in normal landfills and specialist disposal will be required.

Solid wood walls are one of the few carbon negative building materials. When sourced from a sustainable forest the wood used can be of a benefit to the environment having taken CO2 out of the air before being turned into a building material. A solid wood wall is built from wood slab boards and is often created off site, being bought in as one unit. This has the advantage of speeding up construction.

When in place a solid wood wall will provide a durable wall which can take heavy mountings. The breathability of wood allows it to store some of the moisture from a building without being damaged, reducing condensation.

Internal walls are also a major part of controlling noise within a build. To effectively control noise, it is important to understand the difference between sound absorption and sound insulation, as the two are often confused.

Sound absorption relates to the amount of reverberation within a room and its effect on sound quality and intelligibility. Sound insulation, on the other hand, relates to the actual reduction in sound travelling from one area to another through a wall, floor or ceiling. Sound transmission in buildings is a result of both airborne and impact noise.

Solid wooden walls will provide a good form of sound insulation as does plaster board due to there thick natures, thin skinned walls such as stud based timber walls and thin earth walls will require more insulation in order to cut noise to a lower level. The easiest way is to add insulation materials to a wall, these can be in the form of fibre boards or foam insulation which provide a trap for heat and sound (although sound specific insulation does not block much heat).

Insulation materials used on internal walls are similar to those used around other areas of the home. Mineral wool can be used although its use should be kept to a minimum if possible as the small fibres involved can have a negative effect on human health. Natural wool is an ideal choice as it not irritating to human health however it does require more thickness to meet the same specifications of man made insulation. Foam insulation will work the best however this can cause some problems if a wall is required to be remodelled adding to waste that cannot be easily recycled.

The choice of an internal wall is a difficult one for a green builder and there is no one solution.

• Solid wood walls provide a good degree of heat and sound insulation.
• Stud timber framed walls allow for lighter and fewer materials to be used.
• Earth walls allow the use of nature's most available and sustainable resource, but have difficulties in modern building practices.
• Dry walls require an intensive construction and transportation regime.
• Brickwork and blockwork is traditionally costly, heavy and non-recyclable.
• Insulated concrete formwork (ICF) is concrete but has green credentials as very insulating, and quick and simple to build.

Suitable for larger and more repetitive builds where more esoteric materials like cob and earth are not useful.

Finishing walls

As a general principle, use light colours as these mean you will use less lighting without even realising it.

Also try natural materials for screens and blinds, such as bamboo or light wood.

See also the External Walls, Insulation, Wood and Paint articles.