High Mass

High mass refers to systems that use various heavy (high mass) materials, such as concrete, to store heat. High mass is a form of passive control for a heating system that can be very effective when used with solar heating. These systems can store solar heat during the day, when you may need very little heat, and give off their heat at night, when more heat is needed. High mass systems do not produce heat; they merely cause a delay between when heat is put into a radiant panel and when it comes out.