External Wall Insulation Systems
Around 30% of the energy used to heat a typical building is lost through the external walls. External wall insulation systems significantly reduce this energy loss by wrapping the building in a thermally resistant envelope, maximising the internal space, and maintaining comfortable internal temperatures all year round.
External wall insulation systems provide outstanding performance without compromising on aesthetics. Each system can be finished in a wide range of renders and architectural elements.
External wall insulation (ewi) is the most effective way of insulating a building and can be installed as part of eco funded or the green deal schemes.
External wall insulation systems generally comprise firstly of an insulation layer (an element which helps to achieve the requisite thermal performance); and secondly, a protected weatherproof finish (usually a render, although brick slips, tiles, and decorative boards can also be used). Insulating render can also be an advantage in certain locations. Choice of types and sizes will depend on the substrate and design exposure requirements.
Any system selected and installed, should be certified by a notified body.
A selection of traditional finishes is currently utilised within the external wall insulation industry. Dry-dash render is a traditional render application Commonly used.
By this method, dry dashing aggregate is thrown onto the wet render to create a natural aggregate finish. Available in a wide variety of colours, sizes and textures, the practice is relatively cheap.
This is a coloured cementitious render scratched while the surface is still workable, but after the initial setting has taken place. The surface of the render is removed by the action of the scratching tool, and approximately 2 to 3 millimeters of render are removed exposing the open matrix of the aggregate mix. The true colour of the render is exposed with a light even texture.
Wet dash, rough-cast render
This consists of a top-coat render and aggregate mix thrown onto a backing coat in a slurry form, the aggregate being totally encapsulated within the cementitious slurry. The aggregate may be any hard stone of an equal graded size to suit the particular application and creates a “lumpy texture” finish. This method is traditionally widely used in scotland.
An innovation is the inclusion of silicone water-proofers in pre-blended and pre-packed proprietary renders. This development increases the specification and capabilities of polymer renders, particularly for exposed or coastal areas. It can be applied in the conventional manner or machine applied and is now readily available in all the usual colours.
These are sprayed cementitious mixes, pre-coloured and applied by a hand-held machine. This finish is widely used throughout the uk as an economical, easily applied colourful finish for all forms of building type. It has medium-term durability under average conditions.
Smooth/acrylic painted finishes
This can be achieved over a newly rendered surface to give a smooth coloured effect, free of the imperfections that the more natural aggregate finishes can sometimes deliver. A very wide selection of light colours are available.
These are applied by roller or trowel to an approximate thickness of 1.5 to 3 millimeters and are usually acrylic or silicone-based for waterproofing and long term durability. They produce an even, flat-textured, finish.
These are easily applied, and are considered “high performance” finishes. Some cheaper variants might result in the loss opacity of surface brightness over a relatively short life span. High quality acrylics can provide a longer term durability, colour stability, and crack resistance compared to polymer cement finishes. Acrylic variants are available in a very wide range of colours.
These are more resistant to marine environments than acrylics, as they have superior water resistance, but they can be more costly, and come in a smaller range of colours.
This is a thin facing, applied over an insulant to provide a traditional “brick” wall finish. Brick slips are synthetically manufactured
Simulated brick renders
These can also be replicated in coloured polymer to a high standard. Two coloured layers of polymer-modified external cementitious render are applied in 3 to 4 millimeter layers onto a coloured backing. The “brick” pattern is cut into the top layer, exposing an under-layer of differing colour representing the cement joints