The definition of sustainable construction can have many meanings and definitions. In 2006, the UK Government published a “Code for Sustainable Homes”, intended as a single national standard to guide industry in the design and construction of sustainable homes. The Code measures the sustainability of a home against design categories, rating the whole home as a complete package. There are a number of categories within the Code that are directly linked to the fabric of the home in terms of energy use and reduction in CO2 emissions. However, a number of other important areas appear and ‘credits’ can be obtained which make up the final rating for the dwelling. The Code has 6 levels of achievement, from the base level of 1, which is generally just above the minimum requirements of building regulations, to Code level 6 which takes on the definition of a ‘zero carbon’ house amongst other aspects of design. This paper shows the basis of design for a sustainable home, and gives case studies of homes achieving the higher levels of the Code using Autoclaved Aerated Concrete (AAC) construction.