Based on the previous analysis, the buildings under investigation are designed to be served by integrated systems, including the geothermal system, solar energy, drain water heat recovery, and conventional electric or natural gas energy, with limited space and budget. The geothermal system is the main heating system used in this project. The solar system directly transfers energy to the geothermal field, while the recovered heat from drain water will be delivered to the geothermal field, which links to water to water heat pumps. In addition to these energy sources, boilers are designed to provide additional heat to the building through burning natural gas. To operate pumps in each water loop as driving power, electricity is also necessary. Once these systems are combined together, the temperature of the water storage tank is increased to a set point which satisfies the tenants’ requirements. Figure 32.3 depicts the heating system schematic. It visually displays how the solar system, drain water heat recovery system, geothermal system, and boilers connect with the water tank and supply heat to the building.