According to the 2nd Law of Thermodynamics, systems in contact will tend to do what?

The second law of thermodynamics states that systems in contact will tend to move toward a state of equilibrium or balance. This means that when two or more systems at different energy levels (e.g., temperature) come into contact, heat will flow from the hotter system to the cooler system until they reach a point where both systems are at the same temperature. At this point, there is no longer a net flow of heat, and the systems are said to be in balance.

This principle is important in understanding energy transfer and the efficiency of various home systems, especially in terms of heating and cooling. When designing heating, ventilation, and air conditioning (HVAC) systems, for instance, ensuring that energy is effectively managed and distributed relies on this fundamental thermodynamic behavior.

The notion of balance is thus central to many practical applications in energy efficiency and home design, aligning with the principles of the HERS rating system, which evaluates the energy performance of homes.