Skip to the main content.

3 min read

What Is Static Pressure in HVAC?

Credit: Sergei A.


The demand for heating and cooling systems is quite high: In 2018, it was estimated that the yearly demand for air conditioners in America was over 15.3 million units. Given such high demand, it makes sense to examine efficiency in systems by looking at static pressure, a common measure of efficiency and function within HVAC systems.

When it comes to static pressure in HVAC systems, it is important to understand the purpose of the measurement. What is static pressure, exactly? It is the resistance to airflow in the ductwork or other components within the system.

Perhaps the more important question is what is static pressure in HVAC? It is still the same measurement, but the focus shifts towards efficiency and function. How well does the system work upon installation, and how well does it continue to work in the future?


Digging Deeper Into the Static Pressure Definition

To understand what static pressure problems look like, it’s important to start with what static pressure means. Every HVAC system is designed a certain way to handle a certain amount of air going through the ductwork and through the home or business space.

The static pressure is set for optimum functionality of the system, but problems can occur when the installation isn’t handled properly, or the ductwork isn’t properly configured. Heating and cooling a space requires paying attention to installation as well as current operation.

Air circulates through whatever space it has available, but that doesn’t mean that things are optimal. High static air pressure lowers the efficiency and function of the HVAC system.


AirFixture can install underfloor air distribution systems in any space!

  1. Offices
  2. Educational
  3. Government
  4. Libraries
  5. Casinos
  6. Event Spaces
  7. Residential


How to Measure Static Pressure

In order to perform a successful static pressure test, it’s important to get the static pressure measurement. The measurement is expressed in inches of water column, which represents the classic way static pressure was measured. The tool to measure static pressure vs airflow is known as a manometer.

To use the manometer, you have to drill into both the supply and return of the HVAC system in question. The static pressure equation is simple: you must add together the measurement from the return and the supply. If any number is measured initially as a negative, make it a positive for the purposes of the test.

Any static pressure measurement that is over 0.5 inches is considered high, which means that the HVAC system has to work harder to push the air around the air duct and the system at large. Learning how to calculate static pressure isn’t difficult; it’s taking action based on the static pressure formula that can be tricky.


Making Sense of the Numbers

Total pressure is the focus; when the pressure drops or becomes inconsistent, problems with air conditioning are bound to follow. The blower motor is one of the more sensitive components of the system and can be negatively affected by high static pressure.

The amount of air going through the system as a whole can be compared to the health of the human body. When humans don’t get the right amount of air, other health problems spring up.

This is the same for heating and cooling systems; problems with air pressure lead to issues with cold spots in the house, or problems with air flowing to some rooms over others.


Understanding Static Pressure vs Dynamic Pressure

In every system, balance is the key to efficiency as well as performance. Just as the system needs static pressure, it also needs dynamic pressure. So if static pressure is the resistance of flow, then dynamic pressure is when things are in motion.

Total pressure is the measurement of static and dynamic pressures, and the two pressure aspects work together around the clock within a balanced system.


The System Components Make the Difference in Static Pressure

As mentioned earlier, lower static pressure measurements are better than higher ones. Unfortunately, poor installation processes can make it difficult to combat static pressure. The best solution is to begin with proper installation and material selection.

This is where underfloor air distribution systems can add to a system’s efficiency because the underfloor setup operates with a much lower static pressure rating.


Chasing the Balance of Pressures

The hallmarks of high static pressure are easy to detect: noisy systems, impaired function, and a sluggish system that can leave hot and cold spots instead of even temperature control.

Ductwork is also important: the duct static pressure rule of thumb is to have the right size for the right air conditioning system; a one-ton air conditioning unit lines up with roughly 500 square feet of space.

To solve problems of pressure, go back to the basics. Start with quality ductwork and base components like an underfloor air distribution system that’s built for efficient, long-term use. A project, after all, is only as good as the sum of its components.


Let AirFixture Handle Your Pressure Problems

We specialize in providing underfloor air distribution systems that improve employee health, productivity,  and comfort, and that also reduce energy costs.

For more information, contact us today.

5 Myths About UFAD Systems – Air Fixture

5 Myths About UFAD Systems – Air Fixture 

Debunking 5 Myths About UFAD: Underfloor Air Distribution Underfloor air distribution can be a great option for any business or home. Its...

Read More

Theatre or Auditorium Work? Let AirFixture Help!

Auditorium and music hall projects present special challenges for comfort conditioning. AirFixture offers uniquely effective in-floor diffuser...

Read More

How to Avoid Excessive Dust in an HVAC Plenum

A plenum is a great alternative to traditional ducts, and ensuring your plenum stays free of dust ensures proper air circulation. If your HVAC plenum...

Read More