Insulated concreted formwork is the name given to the type of construction where hollow polystyrene blocks (moulds) are formed on site and then filled with concrete.  It is becoming more popular in particular in self-build homes throughout the UK though still in the minority compared to blockwork and timber frame.  Despite its simplicity, this is not a job for a DIY specialist - while there have been occasional problems on site, especially with too much concrete being poured into the moulds and bursting out, it is a highly energy-efficient way to build. 

ICF houses are very warm and structurally sound - higher material costs are usually offset by faster build times and reduced heating requirements.