One of the most important parts of your Heating, Ventilation and Air Conditioning (HVAC) system is the air filter. Besides protecting building occupants from harmful contaminants, the type and efficiency of an air filter determines the amount of electricity required to push the air through and as a result, affects cost.
Saving energy and maintaining energy efficiency also helps fulfill requirements for becoming Leadership in Energy and Environmental Design (LEED1) certified. Utilizing pressure drop as a barometer of when to change air filters provides maximum efficiency and prolongs the life of the entire HVAC system. Every filter manufacturer lists a recommended final pressure drop that determines when it is time to change a filter.
What is Air Filter Pressure Drop?
HVAC air filters are inserted where they can trap contaminants in the system’s airflow. Higher Minimum Efficiency Reporting Value (MERV2) rating filters are denser and can trap more particles, but they also can slow down a system’s airflow rate. Dirty filters will slow down the airflow, as well.
A drop in the rate through which air flows through the system creates a drop in the air pressure moving against the filter. This is air filter pressure drop.
A pressure drop causes an air handler to have to work harder. To maintain the same airflow, the air handler needs to consume more energy. Therefore, the air velocity of the system is not as good a barometer of energy savings as is air filter pressure drop.
The system’s air velocity can be maintained using more energy, but pressure will only come up with either a new filter, one that is less dense, or an alternative filter design. Reducing air filter pressure drop can increase the flow of air through the system without causing the air handler to consume more energy.
Energy Savings and LEED Certification
Measuring air pressure drop is a simple, inexpensive way to contribute to the energy savings and savings maintenance required to become LEED certified. Measuring only air velocity through the system is a less accurate way to determine if a filter needs to be changed or if a new filter design might be necessary.
LEED stands for Leadership in Energy and Environmental Design. Green building companies and companies that wish to brand themselves as good environmental stewards often benefit from LEED certification. LEED certification can lead to higher sales, higher lease rates, and greater preservation of a property’s value. Certification also comes with tax incentives. Additional information can be found on the website for the United States Green Building Council, www.usbc.org.
Published Final Resistance Levels
Manufacturers' recommendations for final recommended pressure drop is intended to illustrate the maximum pressure drop allowed before the system suffers. For example, a MERV 14 filter operating to its recommended final resistance levels can use up 50% of the energy needed to operate the system’s fan. The energy cost to move air through a dirty or improper filter most often outweighs operating to final resistance level.
When to Consider a New Filter
For maximum energy savings, the air filter should be changed when pressure drop has doubled. This could be caused by the filter design or due to loading of the filter with contaminants. This rule of thumb is consistent whether a system is using HEPA filters or pleated filters.
For maximum energy savings, air filter pressure drop needs to be measured and evaluated. This is one large step in the right direction to becoming LEED certified. Measuring air velocity does not give as good an estimate of energy waste as does measuring pressure drop.
Achieve maximum efficiency and prolong the life of your HVAC system utilizing pressure drop as a barometer for energy savings. When the time comes for new air filters for your system, let Advanced Filtration Concepts help you choose the right balance between design and performance. For more information on air filter pressure drop and energy savings, visit AFC on the web, or, contact us to learn more.