Buildings use many types of mechanical systems. However, most of the mechanical design work in residential and commercial buildings deals with HVAC: space heating, ventilation, and air conditioning systems.

• These systems keep the indoor temperature and humidity within a range that provides comfort and health.
• Mechanical ventilation also provides a constant supply of fresh air, to keep pollutants at low and safe levels.

Mechanical installations operate at their best when equipment capacity is adequate. Contrary to popular belief, over engineering has many negative consequences. For example, oversized chillers and boilers tend to cycle rapidly, wearing down faster and causing indoor temperature variations. Another consequence of over engineering in mechanical systems is poor control of indoor humidity.

In high-rise constructions, finding the optimal routes for electrical conduit and wiring can save plenty of material. There tends to be more design flexibility than with mechanical systems, since electrical circuits use less space and can be routed around obstacles more easily. With the aid of MEP design software, conduit and wiring can be laid out while minimizing total circuit length, and avoiding location conflicts with mechanical and plumbing installations.

Lighting installations are the electrical system with the highest energy consumption in most buildings. LED lighting is frequently recommended by energy consultants, since it achieves typical savings of 30% to 90%, depending on the lamp type replaced. Many design software packages can simulate lighting, to determine the optimal number of fixtures and their layout.

HVAC is an area that requires close collaboration between mechanical and electrical engineers:

• Mechanical engineers calculate the space heating and air conditioning loads, to determine equipment capacities.
• Electrical engineers design the electrical circuits and protection measures that allow this equipment to operate continuously and safely.

Plumbing installations are also subject to code requirements. The plumbing design process involves a layout of piping routes,  similar to ductwork in mechanical design and conduit in electrical design. MEP engineers use advanced software to simplify the process and avoid clashes.

Plumbing installations interact with mechanical and electrical systems at many points, and collaboration among design teams is important:

• High-rise buildings normally need water booster pumps, which run with electricity.
• Domestic hot water systems normally use a dedicated water heater, or a heat exchanger connected to a space heating boiler.