The paper presents a new thermal storage concept called Enviro-Core and discusses the barriers represented by the traditional building process with regard to development of integrated energy systems. Enviro-Core may use heavy building waste (crushed and screened) as a storage medium with air as a thermal transfer agent. The storage concept is based on a modular design that will facilitate active control and optimisation of thermal in-put/out-put, and it can be adapted for simultaneous heating and cooling often needed in large service and institutional buildings. Successful development of the Enviro-Core concept may also make a significant contribution with regard to recycling of heavy building waste, reducing the large volumes being deposited at present.