Definition Filter
Air Filters-A Healthy HVAC System and Indoor Air
The filter in your HVAC system has two jobs. It stops undesired particles from entering the ductwork and passing over the internal components, namely the coils. The second job is to clean the air by removing dust and airborne particles which improves the indoor air quality. Modern buildings are constructed to minimize natural ventilation because they seal all the construction cracks and gaps. Have you noticed a lot of dust in your house or office? Maybe smells and odors linger longer than you want them to? Let’s talk filters.
Filter Ratings
Any filter you buy will have something called a MERV Rating. MERV stands for Minimum Efficiency Reporting Values. The MERV rating is an industry-standard system for rating the minimum efficiency of air filters. The MERV rating is a scale from 1 to 20, with 1 being the least effective designation and 20 the most effective. A very economical fiberglass filter would have a MERV rating of 3 or 4, and only traps the largest of airborne particles which generally is bad for the HVAC system and the indoor air quality. A more efficient filter with a MERV rating of 20 will trap almost all particles. As the MERV rating increases, so does the filter effectiveness. If you’re into the more formal definition, here you go:
MERV 20 Particle Size Filtered = < 0.3 microns Used in Industrial Cleanrooms
MERV 16 Particle Size Filtered = 0.3 – 1.0 microns Used in Operating Rooms
MERV 12 Particle Size Filtered = 1.0 – 3.0 microns Used in High Performance Residential
MERV 8 Particle Size Filtered = 3.0 – 10.0 microns Used in Average Commercial
MERV 4 Particle Size Filtered = >10.0 microns Filters out small rocks
Residential Filters
Most home HVAC systems tend to use the lower end filters, MERV 4 or so. While these are the most economical, they actually do little more than stop pollen, dust mites and carpet fibers. Perhaps you have noticed dust accumulating on the horizontal surfaces of your home. Unless you keep your windows open a lot, the dust is a side effect of poor HVAC filtration. If you want to reduce the amount of dust, step up to a MERV 10 or so.
An easy way to pick your filter is by knowing what you want to filter out of the air. Some examples are:
*MERV 5 to 6 – Lint & Heavy Dust Particles
*MERV 8 or 10 – Settling/Average Dust Particles, Mold Spores, Dust Mite Debris, Pet Dander, Pollen
*MERV 11 – Suspended/Fine Dust Particles, Mold Spores, Dust Mite Debris, Pet Dander, Pollen, Auto Emissions
*MERV 12 – Suspended/Fine Dust Particles, Mold Spores, Dust Mite Debris, Pet Dander, Pollen, Auto Emissions, Bacteria
*MERV 13 – Suspended/Fine Dust Particles, Mold Spores, Dust Mite Debris, Pet Dander, Pollen, Auto Emissions, Bacteria, Sub-Pollen Particles, Pollution, Most Viruses
Resist the temptation to upgrade your filter beyond MERV 12. The supply fan for your HVAC system may not be able to overcome the resistance (pressure drop) these filters require. Remember that the resistance of the filter will steadily increase as it gets dirty which will decrease your systems air flow. A good test is to measure the air temperature at one of the supply registers before you upgrade the filter. Then remove the filter and measure the temperature while there is no filter installed. Compare it to the first measurement. The two temperatures should be very close. The last part of the test is to measure the temperature after installing your new filter. If there is a change beyond 3 degrees, you will want to monitor the HVAC systems performance and note if it still heats or cools your home adequately.
Types of Filters
The size of the fan in your HVAC system determines the optimum filter type you can install. The proper filter for your furnace will maximize the particles removed from the air and minimize the loss of efficiency. Below are the most popular types of air filters and a brief description.
* HEPA Filter: Normally not used in residential applications due to the pressure drop, HEPA filters are among the most efficient filters on the market. They operate at an efficiency rate of over 99 percent and remove almost all of the bacteria, most tobacco smoke, cooking oil and sneeze droplets in the air.
* Charcoal Air Filter: This is a filter with carbon deposited inside the filtering media. Also known as activated carbon filter. Charcoal filters are ideal for the removal of odors caused by tobacco smoke, chemicals, and gases.
* Pleated Filter: The pleated filter is the best filter for most residential applications. It is a good option for efficiently removing particles from the air. The filter material is pleated, or folded, in order to increase its overall surface area and consequently trap more particles. The pleats will also increase the life of the filter.
* Electrostatic/Electronic Filter: Electrostatic filters are typically provided as an upgrade when you purchase a new air handling unit. They are a great way to improve air quality without decreasing the efficiency of your fan. Basically an electrostatic field is produced across the filter which attracts airborne particles. This is similar to the bug zapper you might have in your back yard. Since the filter material is relatively thin, airflow reduction caused by electrostatic filters is minimal.
* Bag Filters: This type of filter is not used in residential applications. It is installed in a rack which houses multiple bags of filter media. The bags come in various MERV ratings which makes this a good choice for hospitals or high-end commercial applications.
Value Added Features
You can also find filters with baking soda (Arm & Hammer), antimicrobial properties, pre-filter pad or odor control properties. While these features do not effect the MERV rating, they can be used to enhance the filter’s effectiveness.
About the Author
I am a professional engineer with over 30 years of design experience relating to plumbing and mechanical systems. Visit the Pro Energy & HVAC site.
|
|
Rokinon Slim 58mm High Definition MC UV Filter for Canon T3i T3 T2i XSi XS XTi $7.99 |
|
|
Rokinon 52mm High Definition UV Protective Filter for Nikon D5100 D3100 D5000 + $3.79 |
|
|
NEW Hoya HD High Definition Digital UV Filter 67 67mm $65.00 |
|
|
High Definition 3PC Filter Kit for Sony HVR-A1U $27.99 |
|
|
55mm 55 Hi Definition Filter KIT Sony 55-200mm 18-70mm 75-300mm A55 A33 A390 A65 $11.99 |
|
|
55mm High Definition Filter KIT For Sony 55-200mm 55-200 75-300mm 18-55mm +++ $11.99 |
|
|
Opteka Platinum Series 58mm High Definition Filter Kit Canon $12.96 |
|
|
HOYA 58mm UV HD High Definition Lens Filter 58 mm UK $42.29 |
|
|
HOYA 52mm HD High Definition Digital UV Filter 52 New $44.95 |
|
|
Hoya HD 58mm High Definition Digital UV Filter 58 mm $53.71 |
|
|
Hoya USA HD High Definition Digital UV Filter 55 55mm $39.99 |
|
|
Bower FPC72 Digital High-Definition 72mm Polarizer Filter $19.33 |
|
|
43mm High Definition 3PC Filter Kit CPL UV FLD $24.99 |
|
|
HIGH DEFINITION 30MM 3PC FILTER KIT CPL UV FLD $21.99 |
|
|
HIGH DEFINITION 77MM 3PC FILTER KIT CPL UV FLD $32.99 |
|
|
52mm High definition wide angle + filter UV + lens cap for Nikon D80 D70 $18.99 |
|
|
82mm Professional High Definition 3PC Filter Kit $37.99 |
|
|
62MM HIGH DEFINITION 3PC FILTER KIT CPL UV FLD $27.99 |
|
|
Hoya HD 55mm 55 mm High Definition Protector Filter NEW $50.54 |
|
|
Digital High-Definition 77mm Circular Polarizer Filter $26.00 |
|
|
Digital High-Definition 72mm Circular Polarizer Filter $25.00 |
|
|
Opteka OPT UV 67mm High Definition II UV Filter $2.00 |
|
|
High definition UV CPL FLD filter kit + hood lens for Nikon D60 D5100 D3100 $17.09 |
|
|
VARIABLE NEUTRAL DENSITY ND DIGITAL HIGH DEFINITION HD FILTER 72mm $9.89 |
|
|
HOYA 52mm HD UV High Definition MC Multi-Coated Filter FUJIFILM X-Pro1 FUJINON $42.99 |
|
|
Digital High-Definition 52mm Circular Polarizer Filter $18.00 |
|
|
Digital High-Definition 55mm Circular Polarizer Filter $20.00 |
|
|
Digital High-Definition 58mm Circular Polarizer Filter $22.00 |
|
|
Digital Concepts High Definition 0.5X Wide Angle Lens Macro 3 filters UV 37mm $0.99 |
|
|
Hoya HD High Definition Digital Protector Filter 52mm *USA Authorized Dealer* $33.50 |
|
|
Bower FPC72 Digital High-Definition 72mm Polarizer Filter $19.33 |
|
|
High Definition Lenses Filters For Panasonic DMC-G1 $79.99 |
|
|
0.21x High definition wide angle lens + filter kit + microfiber for Sony A330 $66.49 |
|
|
Hoya HD High Definition Digital UV Filter 77 77mm $68.99 |
|
|
Elemental Bundle 58MM High Definition Lenses and Filter Kit for Canon T3 T3i $94.99 |
|
|
HIGH DEFINITION LENSES FILTERS FOR FUJI FINEPIX S100fs $129.99 |
|
|
High Definition 3PC Filter Kit For PANASONIC DMC-L1K $27.99 |
|
|
Genuine Hoya 52mm HD UV Filter 52 mm Digital High Definition Lens Protector $36.62 |
|
|
Genuine Hoya 52mm HD UV Filter 52 mm Digital High Definition Lens Protector $37.00 |
|
|
Genuine Hoya 58mm HD UV Filter 58 mm Digital High Definition Lens Protector $39.59 |
|
|
Genuine Hoya 58mm HD UV Filter 58 mm Digital High Definition Lens Protector $40.00 |
|
|
Genuine Hoya 62mm HD UV Filter 62 mm Digital High Definition Lens Protector $46.52 |
|
|
Genuine Hoya 62mm HD UV Filter 62 mm Digital High Definition Lens Protector $47.00 |
|
|
Genuine Hoya 67mm HD UV Filter 67 mm Digital High Definition Lens Protector $51.47 |
|
|
Genuine Hoya 67mm HD UV Filter 67 mm Digital High Definition Lens Protector $53.00 |
|
|
Genuine Hoya 72mm HD UV Filter 72 mm Digital High Definition Lens Protector $60.38 |
|
|
Genuine Hoya 72mm HD UV Filter 72 mm Digital High Definition Lens Protector $61.00 |
|
|
Genuine Hoya 77mm HD UV Filter 77 mm Digital High Definition Lens Protector $67.31 |
|
|
Genuine Hoya 77mm HD UV Filter 77 mm Digital High Definition Lens Protector $69.00 |
|
|
Genuine Hoya 82mm HD UV Filter 82 mm Digital High Definition Lens Protector $74.24 |
|
|
Genuine Hoya 82mm HD UV Filter 82 mm Digital High Definition Lens Protector $75.00 |
|
|
Genuine Hoya 52mm HD Circular PL CIR-PL Filter High Definition C-PL CPL 52 mm $54.44 |
|
|
Genuine Hoya 52mm HD Circular PL CIR-PL Filter High Definition C-PL CPL 52 mm $55.00 |
|
|
Genuine Hoya 58mm HD Circular PL CIR-PL Filter High Definition C-PL CPL 58 mm $62.36 |
|
|
Genuine Hoya 58mm HD Circular PL CIR-PL Filter High Definition C-PL CPL 58 mm $63.00 |
|
|
Genuine Hoya 62mm HD Circular PL CIR-PL Filter High Definition C-PL CPL 62 mm $67.31 |
|
|
Genuine Hoya 62mm HD Circular PL CIR-PL Filter High Definition C-PL CPL 62 mm $69.00 |
|
|
Genuine Hoya 67mm HD Circular PL CIR-PL Filter High Definition C-PL CPL 67 mm $81.16 |
|
|
Genuine Hoya 67mm HD Circular PL CIR-PL Filter High Definition C-PL CPL 67 mm $83.00 |
|
|
Genuine Hoya 72mm HD Circular PL CIR-PL Filter High Definition C-PL CPL 72 mm $89.08 |
|
|
Genuine Hoya 72mm HD Circular PL CIR-PL Filter High Definition C-PL CPL 72 mm $91.00 |
|
|
Genuine Hoya 82mm HD Circular PL CIR-PL Filter High Definition C-PL CPL 82 mm $114.82 |
|
|
Genuine Hoya 82mm HD Circular PL CIR-PL Filter High Definition C-PL CPL 82 mm $117.00 |
|
|
52mm High definition multi-coated filter lens kit UV CPL FLD for Samsung EX1 $23.49 |
|
|
Hoya HD High Definition Digital UV Filter 77 77mm $68.99 |
|
|
MONSTER POWER High Definition Video Powercenter for Flatscreen TV Power Filter $39.99 |
|
|
High Definition 2X Telephoto Lens + Filter Kit (UV-CPL-FLD) f/ Sony Nex-3 Nex-C3 $34.99 |
|
|
Hoya HD 77mm 77 mm High Definition Protector Filter NEW $91.61 |
|
|
Rokinon Slim 52mm High Definition Multi-Coated UV Filter – Brand New! $6.99 |
|
|
Rokinon Slim 62mm High Definition Multi-Coated UV Filter – Brand New! $8.99 |
|
|
Rokinon Slim 67mm High Definition Multi-Coated UV Filter – Brand New! $9.99 |
|
|
Hoya HD High Definition Digital UV Filter 77 77mm $68.99 |
|
|
HOYA 52mm HD CPL High Definition Multi-Coated Filter for FUJIFILM X-Pro1 FUJINON $60.99 |
|
|
HOYA 52mm HD Digital UV Filter High Definition Japan 52 $38.99 |
|
|
HOYA 58mm HD Digital UV Filter High Definition Japan 58 $43.49 |
|
|
HOYA 67mm HD Digital UV Filter High Definition Japan 67 $55.99 |
|
|
HOYA 72mm HD Digital UV Filter High Definition Japan 72 $63.99 |
|
|
HOYA 77mm HD Digital UV Filter High Definition Japan 77 $71.99 |
|
|
High Definition 52mm Multi-Coated MC UV MCUV Filter for Nikon Canon Olympus $6.95 |
|
|
HOYA 52mm HD CPL High Definition Filter for Olympus OM-D ED 12-50mm f3.5-6.3 EZ $60.99 |
|
|
HOYA 77mm HD UV High Definition Filter for Canon 5D Mark III 24-70mm F2.8 Lens $76.99 |
|
|
HOYA 77mm HD CPL High Definition Filter for Canon 5D Mark III 24-70mm F2.8 Lens $111.99 |
|
|
Hoya 72mm High Definition HD Protector Digital Filter $58.00 |
|
|
Hoya HD High Definition Digital UV Lens Filter 55mm – USA Authorized Dealer $37.50 |
|
|
Hoya HD High Definition Digital UV Lens Filter 62mm – USA Authorized Dealer $49.50 |
|
|
Hoya HD High Definition Digital Protector Filter 77mm *USA Authorized Dealer* $64.50 |
|
|
77mm High Definition Multi-Coated MC UV MCUV Filter for Nikon Canon Minolta NEW $10.95 |
|
|
Hoya 77mm High Definition HD Protector Digital Filter $63.00 |
|
|
HOYA HD UV 67mm High Definition Filter (NEW) for Nikon 18-105 Canon 100mm Macro $67.00 |
|
|
HOYA HD UV High Definition 82mm Filter (NEW) for Canon EF 16-35mm f/2.8 L II USM $75.95 |
|
|
Rokinon Slim 72mm High Definition Multi-Coated UV Filter – Brand New! $9.99 |
|
|
Hoya HD 82mm High Definition UV Filter NEW Free UK Post $109.78 |
|
|
Hoya HD High Definition Digital Protector Filter 55mm $48.63 |
|
|
Hoya 52mm HD Digital UV Filter High Definition Multi-Coating 52 ~ NEW $38.75 |
|
|
Hoya 55mm HD Digital UV Filter High Definition Multi-Coating 55 ~ NEW $41.48 |
|
|
Hoya 58mm HD Digital UV Filter High Definition Multi-Coating 58 ~ NEW $42.53 |
|
|
Hoya 62mm HD Digital UV Filter High Definition Multi-Coating 62 ~ NEW $49.35 |
|
|
Hoya 67mm HD Digital UV Filter High Definition Multi-Coating 67 ~ NEW $54.50 |
|
|
Hoya 72mm HD Digital UV Filter High Definition Multi-Coating 72 ~ NEW $66.05 |
|
|
Hoya 77mm HD Digital UV Filter High Definition Multi-Coating 77 ~ NEW $71.30 |
