The seasonal changeout of air filters in HVAC systems for public and private buildings is an essential maintenance task, especially when there are significant changes in environmental conditions, such as going from cool to warm or warm to cool weather. Another consideration for seasonal changeouts is changing humidity levels. Properly maintaining air filters ensures better indoor air quality for building occupants, better energy efficiency, and properly functioning HVAC equipment. How does the quality of the air filter affect how often it needs to be changed? Are you changing your air filters too often? In this article, we will answer those questions and more.
Why are seasonal air filter changeouts important?
Most often, property and facilities managers of commercial spaces, educational facilities, office towers, etc. use a prefilter of MERV-8 or MERV-9 efficiency and a MERV-13 final filter because of concerns about airbourne virus spread, and a greater focus on better indoor air quality. Also, managers of companies and institutions are often mandated to follow BOMA Best, Green Buildings, or LEED guidelines, which recommend MERV-13 as a minimum requirement.
Final filters are generally only replaced every 1 to 5 years, depending on the type and quality of the filter in the final filtration stage. Prefilters protect final filters and equipment by removing larger particles, such as large dust particles and objects such as leaves, that can damage HVAC systems.
When a prefilter is working optimally, without restrictions in airflow, It has a lot less static pressure, and the rest of the system doesn’t have to work hard to pull the air behind the prefilter, protecting against dust build-up on coils, motors, bearings, belts, pulleys, and other interior mechanisms.
As long as the prefilter maintains its seal, the amount of dust and particles behind it will be minimal. If there is any bypass in the air handling unit, or if the filter is beginning to show problems with structural integrity, it’s important to note that dust can penetrate and settle, so it will require regular cleaning and removal.
What is the positive impact of properly maintained air filters on the health and well-being of building users?
With cleaner air, there is less sick time and less downtime. Cognitive processes aren’t affected as much. People are more productive in businesses, offices, and educational instituations.
· By using a MERV-13-rated filter or higher, finer particles are removed
· The World Health Organization advises it is most important to remove PM2.5 and PM1, tiny particles that cause the most damage to humans, from the air
· The smallest particles get directly into the lungs and other organs and can affect the cardiovascular system
· Fine particulate matter impacts the ease of breathing and exposes humans to disease
· Cardiovascular diseases start to increase with a higher presence of PM2.5 and PM1
· Ingestion of fine particulate matter leads to fatigue and works against your immune system, forcing it to overwork and keeping it from functioning properly
The importance of selecting the right air filter when doing changeouts
Choose the right type of air filter for your facility. The actual efficiency of your air filter is crucial for particle capture to protect people in buildings or facilities. MERV (Minimum Efficiency Reporting Value) ratings on filter boxes don’t always represent what is actually in the box. See MERV Air Filter Testing in Canada for more details. It’s best to use filters properly tested and guaranteed to perform at their actual MERV ratings. Ask your supplier for guaranteed performance assurance.
Finally, it is important to consider the specific filtration requirements of your building or facility. For example, is your building located in an area with a lot of smog, or is it near a factory? In this case, you will need more robust air filtration as there will be more particulate matter to remove from the air. Suppose you need to schedule changeouts for an office building. In that case, you should monitor for not only PM2.5 and PM1 but also for volatile organic compounds (VOCs) and use MERV-13-A filters for particulate matter and molecular air filters for gasses.
What is the impact of the HVAC system’s performance on energy efficiency?
As an air filter gets dirty as it picks up dust, it collects the dust so that it doesn’t get through into building vents and into the lungs of building users. But as dust builds, it creates a situation where it requires more pressure to push the air through. On constant-speed fans, the filter doesn’t allow as much airflow. Also, static pressure starts to build up and has a negative effect on a constant-speed drive fan. When a new filter is installed, a large amount of air flows through the system. As dust builds up on the filter, pressure increases, which in turn reduces the level of airflow and reduces the amount of air entering the building. At this point, the constant-speed fan is working just as hard as it was when the filter was new, but it is pushing less air through the bottleneck, the clogged filter.
A more modern system is a variable frequency drive (VFD) controlled fan. As the filter becomes clogged, the fan ramps up to push out the designed amount of air. But as it ramps up, it uses more energy, requiring much higher energy costs.
How much could this cost savings be by regularly maintaining air filters using gauges and monitors?
If you’re being billed $0.10 a kWh for energy: when an air filter is new, it will be 0.25 to 0.3 inches of static pressure, and for every 10th of an inch increase, when that rises to 0.4, it costs $24 a year more in energy to pull that through, 0.4 or 0.5 is an extra $48 per filter per year.
Most states and provinces in North America that rely primarily on hydroelectric sources provide less expensive energy. However, for provinces like Alberta, which use gas burners to create electricity, or those that burn coal for electricity —Especially with the rising carbon tax in Canada— it can get quite costly.
In VFD systems, the best time to change a filter is when it reaches twice its initial pressure drop because as it reaches 2X, it is more expensive to keep using it than to replace it.
Some companies, schools, and government offices replace air filters every three months regardless of the pressure drop.
A better solution
McCausland says, “Instead of sticking to a fixed schedule, install a Magnehelic gauge or another manometer, which will register changes in pressure drop. Then, plot and document the readings. Over time, you will have a much better idea of the ideal time to change your filters and can save a maximum amount of energy as well as save on filter costs and labour.”
McCausland adds, “If you can put a filter into a system and observe the initial pressure drop at 0.2, then you should do a filter changeout at 0.4. The documentation on a filter may specify that it should be changed at 2.5 times the static pressure. But if you are paying $0.15 a kWh for electricity, you might decide that it is better to replace it at two times the static pressure to save on energy costs.”
Guidance on selecting air filters based on specific business needs
A lot depends on what space is available in the air handling unit. Some designs restrict the thickness of the filter that can be installed in the HVAC unit. If it’s built into a system and you want to keep that system the same, you may only have one or two inches and sometimes four inches of space to work with for an air filter. That usually means installing a high-quality MERV-8-A or MERV-9-A filter if you want decent air filtration with a low average pressure drop. If you’re using high-quality filters, such as a 30/30® or a 30/30 Dual 9®, it will remove most of the dust and allergens and improve overall air quality. But to take your air filtration to the next level, a proper, full-size MERV-13 filter is better. Another important consideration is to use MERV Actual Filters, e.g. a MERV-13-A 12″ box filter, which will give you the performance of an actual MERV-13 filter over the duration of its life and will not drop to a MERV-10 after the static charge wears off.
How to inspect air filters
Before replacing filters, inspect the existing filters for signs of damage or excessive clogging. A visual inspection can help you identify any issues that need immediate attention, but the “eye test” does not always provide an accurate assessment of whether your filter is functioning correctly or needs replacing. The best way to determine whether a filter has reached the end of its life is to use gauges to determine pressure drop.
Maintaining the coils in your air handling system
Here are a few ways you can maintain the heating and cooling coils in your HVAC system:
· Both the heating coil and the cooling (AKA evaporator) coil must be cleaned and inspected regularly to ensure that your air filtration system does not break down prematurely
· Drain the coils. Do not let any fluid remain on the coils, as it can damage your HVAC system
Frequency: How often should you replace your air filters?
Adjust your air filter replacement schedule based on the specific design and needs of your HVAC system and building conditions. For example, if your building and facility has a large amount of human traffic or if there is a lot of pollution in the metropolitan area, filters will have to be monitored closely and changed more often. During Fall and Spring, it may be necessary to replace air filters more frequently due to increased allergens.
What is more important for air filter performance, efficiency or airflow?
Both air filter efficiency and airflow are crucial. High-efficiency filters can capture more contaminants and ensure the protection of building users. They also protect your HVAC equipment. In certain HVAC designs, air filters can restrict airflow if the MERV rating is too high. Depending on your particular needs, it may be best to use MERV-13-A or MERV-14-A air filters throughout your building. In local problem areas, such as smaller rooms that don’t have proper airflow, use a combination of a portable air cleaner with a HEPA filter and activated carbon filter, which will remove most PM2.5 and PM1 particles and gasses and VOCs.
What to know about HVAC systems and air filter compatibility
Ensure the air filters you choose are compatible with your HVAC system’s design and specifications. Using the wrong filters can result in reduced airflow and can sometimes damage HVAC equipment. A critical consideration of filter and system compatibility is making sure that there are no gaps around the filter housings or in any other part of the air handling system. Even the highest quality air filters will not provide the desired efficiency if there are gaps in the system. It is often possible to retrofit your HVAC system to accept filters with greater depth and lower pressure drop.
The importance of keeping proper maintenance records for air filter changeouts
Keep detailed records of air filter changes, including changeout dates, climate conditions, MERV rating and filter type, and any observed issues. This documentation can show trends in HVAC performance over time and predict the best time to do changeouts for optimal results for the cleanest air and lowest energy usage.
What are the environmental impacts of air filters?
Some filters are recyclable or reusable, which can reduce waste and save money in the long run. However, they are only available in very low MERV efficiencies and cannot perform or protect as well as filters with higher MERV ratings. Air filters using media designed to last longer and to be more energy efficient are the best option right now in terms of environmental sustainability. That means less transportation, less waste, and less energy usage. Read more about air filters and sustainability
How about usage and climate?
In terms of usage, it is advisable to avoid doing changeouts on a fixed schedule because usage has a significant impact on filter life. Pressure drop is the best measure of usage.
In winter, some areas of Canada, particularly in the north, have problems with very fine snow getting into the HVAC system and on the filter. When it builds up, it can create problems and reduce the filter’s life. A good solution is to move the front filter to a second position in colder months and use a preheat coil so that snow and everything else will hit the preheat coil and reduce stress in the air handling unit. It lets the airflow through, and the filter doesn’t get as dirty. Certain climate conditions affect where to locate your filters within your system.
There are standards and guidelines for buildings to draw in a certain amount of outdoor air to maintain a healthy indoor environment, as it replenishes oxygen levels and allows people to breathe better. There is a need for better circulation and filtration of return air. Without proper recirculation, the air inside a building can become very unhealthy.
Much of the dirt and dust present in the air is generated indoors, along with the pollution that comes from outdoor air. Examples of indoor sources include dust and dirt from people’s hair, bodies, shoes, and clothing. Additionally, volatile organic compounds (VOCs) are released by furniture, carpets, cleaning products, and other items. If you’re not getting enough outdoor air entering the building and dealing with a lot of recirculated air, unwanted particles will linger without the right amount of ventilation and air filtration. When this happens, people tend to complain about headaches, dizziness, fatigue, and cognitive levels decline.
Benefits of regular record keeping for HVAC systems and air filter changes
An essential part of record-keeping in HVAC is measuring and recording energy curves from VFD-controlled fans, and when air filters are changed, noting the static pressure and fan build-up readings. The best way to establish the optimal time for a changeout is when the fan reaches the point where it’s drawing too much energy. There will be different pressure levels at other times, e.g. periods of harsh weather and changing environmental conditions like high pollution.
McCausland talks about the impact climate can have, “In Vancouver, we get a lot of rain. On those rainy days, air filters don’t have to work as hard because a lot of particles are washed out as the water molecules pick them up, and then they drop to the ground and are swept down the drain instead of floating in the air. If you keep records of precipitation, you’ll know that if there is an early snowfall, filters may last longer. Also, with a longer wildfire season, there may be a need for more frequent filter changes in affected areas.
When should you change your air filters?
Many companies and organisations do air filter changeouts on a fixed schedule, for example every three months, and in that case some feel that there is no need for detailed record-keeping. The problem with this according to McCausland is that administrators base the changeout term on specifications of high-quality filters and then to save money, purchase lower-quality filters and expect them to perform the same. In these situations, he says, “When these filters are left in too long, in the worst case scenario, these filters can collapse and get sucked in the air handling unit and cause extensive damage.”
Another maintenance issue is when companies, organizations, or schools schedule maintenance for prefilters based on a fixed schedule due to a lack of available labour from contractors. Sometimes, schedules must be set a year in advance to be able to keep up. Record keeping will be less valuable in that case. It also means that they may end up paying too much in filter costs and may not save as much energy as possible by doing changeouts based on pressure drop instead of time. Final filter changeouts are usually planned well in advance.
Professional Assistance when planning changeouts
In most cases, for commercial or public building air filtration systems, it is best to consult with an air filter expert. Often, there is no cost to you to meet with an expert. They can provide guidance on filter selection, equipment selection, maintenance, and system optimization over the life of the HVAC system.
Regular Maintenance of air filtration systems
Along with seasonal changeouts, establish a proper maintenance schedule, including checking for gaps that might develop in the air handling system and equipment damage in your HVAC system. Such maintenance can help extend the life of your equipment and improve indoor air quality.
In conclusion, seasonal air filter changeouts are crucial for maintaining a healthy indoor environment and sustaining particle capture and energy efficiency in HVAC systems for public, industrial, and commercial buildings. By considering this, businesses can ensure that their HVAC systems operate optimally, reduce energy costs, and provide a comfortable and healthy space for building users.
To consult with an air filtration expert, or for additional information, please use this contact form and a Camfil air filtration expert will help you with questions and requests.
About Camfil Canada Clean Air Solutions
For over 60 years, Camfil has been helping people breathe cleaner air. As a leading manufacturer of premium clean air solutions, we provide commercial and industrial systems for air filtration and air pollution control that improve worker and equipment productivity, minimize energy use, and benefit human health and the environment. Read more about Camfil Canada
With information from Bill McCausland, Camfil Canada
Camfil Canada Inc.