REDUCTION IN HEATFLOW
Heat moves naturally from areas of high to lower heat within your house, and all the building materials used in your house either absorb heat or help to transfer it. If your home is heated in winter, that hot air will continually try to move to the outside of your house, where the air is cooler. In the summertime, hot air from the outside will constantly try to flow into the cooler space in your house. Insulation works to prevent this transfer of heat.