Solar passive homes also use convection and radiation physics to keep the house warm or cool according to the needs of the dweller. Heat, like in solids, also circulates in liquids and gases. Warmer fluid or gases rise and cooler fluid and gases sink. This is because warm water or gases are lighter than cooler ones because the molecules are further apart from each other. If you ever had a house that had a basement, you will find that the air is warmer on the ground floor that in the basement. The air in the second or third story will be extremely warmer than the basement. A south wall with less wind and more sun will use convection to pull heat into the house’s interior.

            Radiation is also a component of passive solar homes. Radiant heat radiates by moving through the air and air molecules from warmer areas of the house to cooler. Two types of radiation are used in this heating system. Solar radiation and infrared radiation work hand and hand during this process. When the radiation lands upon an object it is then either absorbed or reflected. This action is determined by the type of material the radiation strikes and how close the molecules of that material are.