Masonry construction - the dominant construction style for new residential buildings in Germany - can and must demonstrate its sustainability in terms of energy-efficiency. The M1 energy-plus masonry house is a pilot project that provides the first practical demonstration of how the benefits of masonry construction - such as its loadbearing capacity, fire safety and sound insulation - can be combined with current and anticipated energy-efficiency standards. A compound blockwork system with different bulk densities and strength classes has been used here for the first time, combining all the advantages of high thermal insulation and heat storage in a monolithic construction (YTONG Energy ). With simple, well-thought-out design details and carefully matched technical construction equipment, masonry energy-plus houses are no longer just a vision. The main focus of the M1 project is to develop a cost-efficient and saleable product which opens up new opportunities for consumers, designers and developers alike.