8 Essential Engineering Calculations in Modern MEP Design

Attention to detail is crucial when it comes to engineering calculations in MEP design. Every number you input into your calculation matters.

Making a wrong assumption or putting a decimal in the wrong spot could wreak havoc on your entire system. You could run into burst pipes, electrical overloads, or inefficient HVAC systems. That’s not something you want to be responsible for.

Don’t worry – we’ve got you covered. Let’s talk about the top eight calculations you need at your disposal if you’re in the middle of designing systems.

1. Load Calculations

Load calculations are essential when you’re designing HVAC systems. We’re referring to heating and cooling loads, or essentially how much energy you need to maintain a comfortable temperature inside of a building.

A few things you’ll need to keep in mind include:

• Sensible Load: Heat added or removed without changing moisture content.
• Latent Load: Heat related to humidity changes.

2. Electrical Load Analysis

As simple as it sounds, one of the main goals of electrical engineers is to figure out what it takes to keep the lights on. They need to be able to crunch the total demand of all connected devices and apply demand factors.

On top of that, engineers need to ensure the infrastructure can handle peak loads without dipping breakers. Electrical engineers are setting themselves up for nuisance tripping or system failures without conducting an accurate load analysis.

3. Heat Transfer and Thermal Loads

If you’re working with radiant floors, chillers, or boilers, that means you’re managing heat. If you’re dealing with heat, that means you need to calculate thermal energy transfer

The standard equation for this is: Q = mc∆T

• Q = Heat transferred
• m = Mass flow rate
• c = Specific heat
• ∆T = Temperature difference

These types of calculations can get complicated fast. Thankfully, there are tools you can use to help.

For example, you may be starting a project where you need to figure out surface angles in radiant designs. You might need to calculate trigonometric equations just to find the right slope for a run of pipe.

4. Pipe Sizing for Hydronic Systems

Water is responsible for moving heat in many MEP setups. You must size your pipes correctly.

Too small pipes will result in reduced pressure. Pipes that are too large for your job mean you’ll have sluggish system response and wasted materials.

You shouldn’t guess when it comes to figuring out pipe sizing for hydronic systems. Some of the things you’ll need to account for include:

• Flow rate
• Friction loss
• Velocity

5. Ductwork Sizing and Airflow

Having proper duct design keeps energy consumption low and airflow balanced. Make sure you figure out what CFM (cubic feet per minute) you need in each space. Then size your ducting for the least amount of pressure loss possible.

Go with one of the following methods:

• Equal friction method
• Static regain method

6. Pump and Fan Head Calculations

Have you noticed that your pump makes terrible sounds each time it starts? You may have forgotten the head loss math. Total head (static + dynamic) tells you what your pump or fan needs to overcome.

Your calculations depend on the following:

• Pipe length and material
• Number of fittings
• Flow velocity

7. Acoustical Calculations

The last thing you want to design is a mechanical room that sounds like a jet engine. Vibration control and sound level come down to mathematical calculations, not just getting lucky with your insulation.

A few things you’ll need to work out include:

• Decibel drop across barriers
• Sound transmission class (STC) ratings
• Duct breakout noise

8. Energy Modeling and Simulation

If you’re working toward LEED or simply want high performance, energy modeling will give you a good picture of what you’re working with before the first wire gets pulled.

To do this, you’ll need to account for the following:

• Thermal envelope performance
• Lighting controls
• Equipment schedules

It’s a what-if playground. Want to know how triple glazing beats double in your climate? Model it.

Final Thoughts

Figuring out these calculations makes you better at your job while you save time, money, and energy. Whether you’re using a tool or running these calculations by hand, it’s important to know the details behind the numbers. Your payoff will be a flawlessly running system thanks to the mathematical calculations you did to prepare.