The Attic Flats Project uses a simple saddle roof technology that enables apartments to be built on to the top of existing low and medium-rise blocks of flats. Not only does this provide new, high quality accommodation at comparatively low-cost, it also refurbishes and improves the energy efficiency of the existing dwelling stock. By using the same infrastructure and requiring no extra land, 60 per cent of the cost of a dwelling is saved. Of the 400 flats built to date (1990), 95 per cent have been built by construction cooperatives, using the unskilled labour of their members.