MEP is an acronym that stands for mechanical, electrical and plumbing engineering. These three technical disciplines encompass the systems that make building interiors suitable for human occupancy. MEP installations are addressed together due to the high degree of interaction between them, and also to avoid conflicts in equipment locations - a common problem when electrical, mechanical and plumbing systems are designed in isolation.
Working with qualified MEP engineering companies brings many advantages: installation costs are reduced by optimizing material requirements, while achieving high performance and code compliance. This is very valuable in New York City, where building ownership costs are very high and construction codes are very demanding.
In addition to the NYC Building Code, there is a dedicated code for each of the three MEP fields:
- NYC Mechanical Code
- NYC Electrical Code
- NYC Plumbing Code
Keep in mind that additional codes apply. For example, the NYC Energy Conservation Code has requirements that affect all MEP systems, and any building system with combustion appliances must adhere to the NYC Fuel Gas Code.
Given the complexity of MEP systems, modern engineering consulting firms use software to speed up the design process. Simple and repetitive tasks are automated by a computer, while MEP design engineers can focus on taking the best decisions.
Before proceeding with any project that involves MEP installations in NYC, keep in mind that there are licensing requirements for both design professionals and installation contractors. Only a Registered Design Professional (RDP) can get MEP designs approved with the NYC Department of Buildings, and only licensed contractors can get work permits.
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M: Mechanical Engineering
Various types of mechanical systems are used in residential, commercial and industrial buildings. However, three types account for most of the mechanical design work in multifamily and commercial constructions:
- Space heating
- Air conditioning
- Mechanical ventilation
These systems interact to keep temperature and humidity within a range that provides comfort and health. Mechanical ventilation also ensures that enough fresh air is supplied to keep pollutant concentrations at low and safe levels.
Mechanical installations operate at their best when equipment capacity is adequate; contrary to popular belief, over engineering brings many negative consequences. For example, oversized chillers and boilers tend to cycle rapidly, creating room temperature fluctuations and wearing down equipment at an accelerated pace.
Another consequence of over engineering in mechanical systems is poor control of indoor humidity. ASHRAE recommends keeping relative humidity between 30% and 60% to make indoor spaces optimal for human occupancy, and there are negative consequences when humidity falls outside this range for extended periods. For example, low humidity can irritate the skin and airways, while high humidity stimulates the growth of mold and bacteria.
Other than sizing HVAC equipment correctly, mechanical design involves laying out optimal routes for heat distribution systems: air ducts, hydronic piping or steam piping, whichever applies for the project. If combustion appliances are used, which is the case for most space heating systems in NYC buildings, these must be properly vented to ensure that harmful combustion products are removed.
E: Electrical Engineering
In high-rise constructions such as those commonly found in NYC, one of the main challenges in electrical design is defining the optimal routes for conduit and wiring. However, there tends to be more flexibility than in mechanical systems, since electrical circuits require much 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 lengths, and avoiding location conflicts with mechanical and plumbing installations.
Lighting installations are the electrical system with the highest energy consumption in most NYC buildings, and engineering consulting firms often suggest LED lighting for this reason. Many MEP design software packages are capable of simulating lighting, in order to determine the optimal number of fixtures and their locations.
HVAC is an area that requires close collaboration between mechanical and electrical engineers during the MEP design process. Mechanical engineers calculate heating and cooling loads to determine equipment capacities, while electrical engineers design the electrical circuits and protection measures that allow this equipment to operate continuously and safely. In NYC, only furnaces and boilers use mostly fossil fuels as an energy source; air conditioners, chillers, air-handling systems and hydronic pumps all work with electricity in the vast majority of cases.
P: Plumbing Engineering
Plumbing installations in NYC are also subject to various technical requirements. Just like mechanical and electrical installations, plumbing requires laying out complex piping routes, and MEP design software widely used by engineering firms to simplify the process.
Plumbing installations interact with both mechanical and electrical systems at many points, which emphasizes the importance of collaboration among design teams:
- High-rise buildings typically need water booster pumps, which run with electricity.
- Domestic hot water systems typically get their heat through one of the following configurations: a dedicated boiler, a heat exchanger connected to a space heating boiler, or an electric heater (a conventional resistance heater or a heat pump).
Fire protection design can be challenging, since NYC codes are especially demanding in that technical field. In addition to the applicable codes from the NYC Department of Buildings and the National Fire Protection Association (NFPA), Local Law 26 of 2004 makes automatic fire sprinklers are mandatory for all business occupancies taller than 100 feet. The law applies retroactively even for existing constructions, where the deadline to complete the building upgrade is July 1, 2019.
Added Value of MEP Design
When designing building systems, an integrated MEP engineering approach yields better results than specifying each building system in isolation. Interactions between building systems can be especially difficult to coordinate when the design process is isolated, and equipment location conflicts are very likely.
If a modern MEP design software is used, the value of the 3D model produced during the design phase goes beyond the construction process. The model can be conserved as reference for maintenance activities, and can be updated along with the building during a major renovation. In general, a building with a MEP engineering model is easier to manage and service than another building where only conventional construction plans are available.