We want the external walls to do two things: to be airtight, but also to be breathable. These two are often confused. 'Airtight' refers to the passage of air - we don't want accidental leakage of air into or out of the building. That would mean gaining cold air or losing heat. 'Breathability' refers to the passage of moisture. We do want any moisture to move from the inside of the building to the outside and not get trapped by an impermeable layer.
The original grey-brown pebbledash on cement render was not very breathable. It was also very, very ugly. So we decided to replace it with a breathable render. We used Baumit's UniRend system. This is a basecoat of KZP 65 lime cement and a topcoat of SilikonTop silicone resin render.
Pegasus Externals have done a superb job, totally transforming the look of the EcoBungalow. The architect - Russel Hayden - used some deceptively simple colour changes:
We always rather liked the 1970s engineering brick panel around the old front door and bathroom windows, providing relief from the pebbledash (hidden behind the long-gone leylandii in the photo). Using the grey render to tie the windows together on the front elevation provides a nod towards the building's original look.
The proportions of the rear garden elevation were quite uncomfortable, with the bungalow raised above the garden above an undercroft. This gave a large expanse of pebbledash. Using the grey as a 'plinth', the elevation is broken down into a clear base and upper storey.
The access to the garden was convoluted: through the living room, into the conservatory and back on yourself down some unattractive steps. The new layout provides generous steps directly from the living area. These are rendered grey to visually form part of the 'plinth', and so are integrated into the building rather than being an afterthought.
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