Decreasing the energy consumption of heating, ventilation and air conditioning (HVAC) systems is
becoming increasingly important due to rising cost of fossil fuels and environmental concerns. Therefore,
finding novel ways to reduce energy consumption in buildings without compromising comfort and
indoor air quality is an ongoing research challenge. One proven way of achieving energy efficiency in
HVAC systems is to design systems that use novel configurations of existing system components. Each
HVAC discipline has specific design requirements and each presents opportunities for energy savings.
Energy efficient HVAC systems can be created by re-configuring traditional systems to make more strategic
use of existing system parts. Recent research has demonstrated that a combination of existing air
conditioning technologies can offer effective solutions for energy conservation and thermal comfort. This
paper investigates and reviews the different technologies and approaches, and demonstrates their ability
to improve the performance of HVAC systems in order to reduce energy consumption. For each strategy, a
brief description is first presented and then by reviewing the previous studies, the influence of that
method on the HVAC energy saving is investigated. Finally, a comparison study between these
approaches is carried out.