Most people think making their home more efficient is mostly insulation, this is partially right. Insulation is only half of what makes your home efficiently warm in the winter and cool in the summer. The other half of the equation is known as 'Thermal Mass'. Mass in terms of residential construction is essentially any hard, dense, heavy material. A concrete block is a good example of thermal mass. Greater mass means the greater potential to store heat, kind of like storing power in a battery. Dense materials such as concrete store and transmit/conduct heat quite well.
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