The first step in designing any heating or cooling system is to understand the building the system will supply. It could range from a 200-year-old building with little or no insulation, single pane windows and high rates of air leakage, to a contemporary structure built to the latest energy conservation standards.
For most buildings, and over many decades, customary practice was to decide on the fuel source, select the type of heat emitters to be used, and then size a heat source to maintain a selected interior air temperature (typically 68-72ºF) under the coldest expected outdoor temperature. Although this approach has led to acceptable installations, it often did not address issues such as ideal comfort, reducing emissions or energy use strategies that could be mutually beneficial to the consumer, the energy supplier and the environment.
The long-standing “customary” approach to building heating and cooling is changing. Modern building designers are employing increasingly wholistic strategies that consider more than the simple thermodynamic balance of matching heating or cooling source equipment to building loads.
Because buildings represent approximately 40 percent of the total energy used in North America, energy conservation efforts, both voluntary and mandatory (in the form of building codes and other regulations) have accelerated over the last decades. These efforts have resulted in buildings that can maintain comfortable interior conditions, such as those based on ASHRAE Standard 55, while using less a 1/3 the energy per square foot of floor space that was required 50 years ago.
Other wholistic design considerations include increased attention to indoor environmental quality, adaptive use of renewable energy and reducing carbon-based emissions.
Collectively, these new design considerations allow contemporary buildings, as well as rehabilitated structures, to serve their intended purposes with minimal environmental impact. Extrapolating these advancements into the future suggests that buildings may eventually be environmentally benign as well as energy self-sufficient.