In order to understand how insulation works, it’s much easier if you understand heat flow. For you to successfully understand the way this works, you should know what each of these words: “Conduction” – Meaning the way heat flows through a material; “Convection” – How heat circulates through liquids and gases; and “Radiation” – Heat traveling in a straight line, heating solids in its path and absorbing energy.
Regardless of how heat travels, another thing to think about is that heat flows from warm to cool until there is no temperature difference. In other words, in the winter heat flows from all directly-heated spaces and heat can also flow indirectly. So, heat can flow directly outside from attics and basements, and it can also flow indirectly through ceilings, walls, etc.
What’s good to know is, in order to maintain comfort in your house, the heat you lose during the cooler seasons must be replaced by your heating system, and the heat you gain during the hotter seasons needs to removed by your cooling system.
You should always have your home properly insulated to control the heat flow in and around your home.