Choosing the Best Air Filter In the last few decades, more emphasis has been placed on making new Winnetka-area homes tighter for greater energy efficiency and comfort, and upgrading older homes with air sealing and insulation for the same purposes. This is great news for homeowners’ wallets and the environment, but it is not good news for indoor air quality, and the issues poor air quality creates for health, the HVAC system and home.

Fortunately, however, the development of better air filters has met the demand of this pitfall of tightly sealed and under-ventilated homes. It may take a little homework, but choosing the best air filter for your Evanston area home is well worth the effort. Here are some tips to get you started in the right direction.

3 Factors For Choosing the Best Air Filter

When choosing the best air filter for your home, it is important to understand the criteria and qualities that define the “best”. Keep in mind what may be best for you may differ from what is best for your neighbor.

  • Particulate capturing: The efficiency of an air filter in terms of particulate-capturing ability is important to consider in regards to healthful indoor air quality, and protecting HVAC system components. There are many filter ratings to consider when choosing the best air filter for your purposes.
  • Filter resistance: All air filters cause some level of airflow resistance as air is pulled through filter fibers. This causes a pressure drop across the furnace blower. The rate of airflow resistance and pressure drop depend on the density and cleanliness of the air filter. The pressure drop is an important factor for choosing the best air filter because it is a good indicator of how much more energy the blower motor needs to use in order to do its job of pulling air through the filter and forcing the air through the supply ducts.
  • Correct size and fit: Choosing the best air filter means selecting the right size, and making sure there is no air bypass around the perimeter.

Filter Efficiency and Healthful Indoor Air Quality

To help put indoor air quality and its effects in perspective, consider that indoor air quality in the average home is more polluted than city air. The contaminants and elements affecting indoor air quality, which are carried or created inside the home, become trapped and free to circulate through the home and affect the health and comfort of household members. When choosing the best air filter for your Glenview area home, consider how you may want a filter to capture the following common household contaminants.

  • Dust and pollen: Airborne dust and pollen is a lung irritant, especially for household members who suffer from respiratory issues such as asthma, allergies and COPA.
  • Viruses and bacteria: Dust particulates also carry viruses and bacteria that easily infect hosts during the dry heating months.
  • Mold spores: Mold and mildew growth are issues in many homes, and can cause odors and create health ailments.
  • Pets: Pet dander is a lung irritant for many people.
  • Auto emissions: Trace amounts of auto emissions are found in practically all homes. If you have an attached garage, your home is more likely to harbor auto emissions in greater quantities.

Filter Efficiency and the HVAC System

The HVAC system accounts for about half of the typical home’s energy budget. Moreover, the HVAC system is an expensive investment which should be protected with a good quality air filter. However, choosing the best air filter to protect the HVAC system also requires choosing a filter that won’t cause excessive wear to components by the pressure drop and one that won’t increase energy bills more than necessary.

  • HVAC efficiency: HVAC efficiency is affected by debris accumulation that hinders heat exchange, and an excessive pressure drop that consumes more electricity than optimal conditions to run the blower. A pressure drop is created by a filter that is too dense to allow adequate airflow to pass, or from a debris-clogged air filter. When airflow is restricted too much, a furnace can overheat and shut down. The evaporator coil of the A/C or heat pump system suffers heat exchange depreciation, which harms and hinders the function of other vital components like the compressor and electronics.
  • HVAC protection: It’s the job of a forced-air HVAC system to circulate household air many times a day in order to heat and cool the home. This introduces airborne contaminants to HVAC components, where they accumulate on the surfaces of the furnace, A/C, air ducts and any add-on equipment, such as a heat-recovery ventilator (HRV). Debris accumulation causes excessive wear to the blower motor, which is a costly repair if the motor fails. In the worst case, the wrong air filter or a filter that is not changed regularly can cause a complete system failure. Moreover, debris accumulation on ductwork walls contributes to poor indoor air quality.

Considering Filter Efficiency and Pressure Drop

Choosing the best air filter for your home begins with a pen and paper. Write down the size of the air filter you need, and the contaminants that you want removed from indoor airflow. For instance, if there are members in your home with respiratory ailments, you will want a filter efficient enough to remove allergens, mold spores and dust mite parts. Mid-efficiency air filters offer this capability. If you want even more healthful indoor air quality by removing germs and viruses, you will need a higher efficiency filter.

If you are more concerned with protecting HVAC components and promoting energy-efficient operation, a mid-efficiency filter should suffice. Therefore, you select filters at the same pressure drop, and compare which contaminants they capture. Following are common filter efficiency ratings you will see on filter packaging and labels.

  • Pressure drop: The best rating and indicator of filter airflow resistance and subsequent HVAC energy usage is the pressure drop. When you compare filters at the same pressure drop, you can base your purchase on filter cost and the contaminants that it captures.
  • Sustained efficiency: The sustained efficiency of an air filter indicates a filter’s particulate-capturing ability during its manufacturer recommended lifespan (e.g. three months). The sustained efficiency won’t indicate energy usage considerations, but it will give you an average efficiency, as opposed to initial or new efficiency, of its ability to capture and hold various contaminants.
  • MERV: MERV is perhaps the most widely used filter efficiency rating. MERV is an acronym for minimum efficiency reporting value. MERV numbers indicate the minimum percentage of particulates a filter will capture according to the size of particulates in microns. MERV numbers span from 1 (low efficiency) to 16 (high efficiency). Mid-efficiency filters are rated MERV 5-8, and are generally good for both particulate-capturing ability and HVAC protection and efficiency. Avoid filters rated MERV 1-4, which do little more than remove the very largest particles from household airflow. MERV 9-12 filters are higher efficiency, which you would select if you want very good indoor air quality, and you are willing to pay a little more on your energy bills. MERV 13-16 filters are thick high-efficiency filters that are typically used in hospital settings, and places where very clean air is vital.

Common Filter Types

Filters are available in all types of designs and materials. The type of air filter you choose determines cost and care. Disposable mid-efficiency filters, for instance, last about three months so expect to change the filter at least each season. Permanent or washable filters may last as long as eight years. These filters cost more, but save you time and money in the long run. Following are common filter types and designs to ponder when choosing the best air filter for your budget and time.

  • Mid-efficiency pleated filters generally do a good job of capturing airborne contaminants and not hindering HVAC efficiency. Filters in this range typically carry MERV 5-7 numbers. However, expect to change and dispose of these filters every one to three months.
  • Higher-efficiency pleated filters are more dense and/or thicker than mid-efficiency pleated. These filters may also carry an electrostatic charge to capture contaminants by attraction, as well as impaction. Be sure to look for a pressure drop rating when you get into filters in this efficiency range so that you are aware of the airflow resistance on HVAC equipment and your pocketbook.
  • Permanent electrostatic filters last up to eight years. They are housed in solid frames with removable media that you may wash by hand or, in some instances, place in the dishwasher.
  • High-efficiency filters last up to one year, and cost substantially more than less efficient filters. If you are considering installing high-efficiency air filters (e.g. MERV 13-16), ask your HVAC professional to evaluate your furnace blower and air ducts to see if any modifications are required.

Remember, your air filter only works as designed if it fits snugly and you change or clean it as recommended by the manufacturer. For more information about choosing the best air filter for your Winnetka area home, please contact us at Roberts Heating & Air Conditioning.

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