Final answer:
Energy in a building's heating system is transformed from usable chemical energy to less usable thermal energy, with some of the heat inevitably wasted to the environment. This loss is due to inefficiency in the heat transfer process and is inherent in energy conversions, known as energy 'degradation'.
Step-by-step explanation:
In a building's heating system, energy is transformed from a usable form into a less usable form mainly through the process of heat transfer. For example, a building may be heated using a gas burner, which converts the chemical energy of the gas into thermal energy through combustion. This thermal energy is then used to heat the air or water, which is distributed throughout the building to maintain a comfortable temperature for occupants.
However, not all the thermal energy produced from the gas burner is used for heating the space; some of it is lost to the surroundings as waste heat. This is inherently inefficient as the heat is transferred to the environment at a lower temperature and is no longer useful for doing work, such as heating the building. This concept is known as the 'degradation' of energy, because the potential for the energy to do useful work is reduced. Efficiency improvements in building systems aim to reduce energy wastage and enhance the proportion of energy that performs useful work.
In thermo- dynamics, this inefficiency is explained by the second law of thermodynamics, which states that all energy transformations result in some energy being transformed into a state that cannot be used to do work, often in the form of low temperature waste heat.