Indoor comfort is all about distributing cooled or heated air throughout the house in the most energy efficient and effective way. Indoor air quality is about making sure that air is as clean and healthy to breathe as possible. As it turns out, accomplishing both can be a challenge. The components of indoor air include everything from everyday housekeeping issues like common dust to toxic microorganisms. There’s something in the air to annoy or irritate almost anyone.

Inorganic dust is made up of:

  • Dirt particles
  • Soot and ash
  • Paint particles
  • Chemical particulates

Biological air contaminants includes:

  • Pollen
  • Epidermal skin cells shed by humans
  • Mold and bacterial spores
  • Algae
  • Insect parts—mostly dead dust mites

Floating fibers generically described as lint may be carpeting and clothes fibers, hair from humans and pets, bits of spun fiberglass insulation, plant fibers and even spider webs and cobwebs.

No wonder, then, that the Environmental Protection Agency has found the indoor environment in homes to be typically as much as two to five times more polluted than outdoor air. In part, we’ve created the situation ourselves as we’ve made today’s homes more energy efficient than ever by airtight construction methods. The lack of air exchange with the outdoors permits indoor toxins to accumulate and concentrate to levels previously unknown.

Filter Efficiently, Change Often

The blower in the typical residential HVAC system circulates an average of 1,400 cubic feet of air per minute. That’s a lot of air in continuous motion and a load of airborne particulates moving along with it. The front line for removing these particles from your breathing air is the filter inside the HVAC system.

Installed in the air handler, the system air filter screens all air moving through your return ductwork as it’s pulled back to the furnace or air conditioner from every room in the house by the suction power of the blower. As long as the system is running, air is being filtered and the filter is slowly accumulating trapped particulates. Manufacturer’s recommendations may call for filter changes at intervals up to every three months. Most HVAC experts, however, advocate monthly changes, particularly during the height of heating and cooling season. Filters are typically less expensive when purchased in multi-packs at your local home center, and the filter change procedure is a simple DIY task anyone can do. So, monthly changes make sense from an air quality, energy efficiency and economic standpoint.

Which Filter?

All filters are not created equal and that’s a good thing. Not every filter is right for every HVAC system or indoor air environment. Occupants of homes differ, too, in their air quality needs. Households that include individuals sensitive to airborne particulates or susceptible to respiratory infections will obviously require a higher standard of filtration. But how do you know what level of filtration you can expect from a particular make or model? Just ask MERV.

MERV is short for Minimum Efficiency Reporting Value, a system that designates the efficiency of air filters by assigning a numerical rating between 1 and 16, ranging from the least to the most efficient filtration. Most manufacturers prominently display a filter’s MERV rating on the packaging so you can compare different efficiencies at a glance. MERV ratings are determined by laboratory tests devised by the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE).

MERV 1 to 4

These filters are generally the original equipment filters typically included with the system when you buy it.  Among HVAC technicians, they are often regarded as “throwaway” filters. However, many homeowners will simply choose to replace these original filters with the same type for the life of the system. In most cases, that’s a bad choice. These flat panel filters with a filter media that is usually composed of spun fiberglass represent the bottom of the filtration efficiency ladder. Filters in this MERV range are designed to simply remove the largest particulates in the air—basically the stuff you can actually see floating around—in a size range of 10 microns or larger. They are most useful for the purpose of protecting moving parts in the system from wear and tear, not for optimum indoor air quality.

MERV 5 to 8

While still in the disposable class of filters, these models utilize cotton or polyester pleated filter media. By pleating the media, the available filtration surface area is greatly increased. Homeowners who upgrade to filters in this range can expect efficiency that removes over 90 percent of airborne particulates is a size range of 3 to 10 microns. This includes all forms of dust and lint, pollen, mold spores, pet dander, hair spray and other aerosols.

MERV 9 to 12

For superior indoor air quality, these pleated filters protect by removing 95 percent of particulates down to a size of 1 microns. Filters in this range will begin to obstruct system airflow if they are left in place when they are dirty. Therefore, homeowners who choose this superior level of protection must also assume greater vigilance and more frequent cleaning or replacement to sustain proper airflow.

MERV 13 to 16

While these filters offer the gold standard in air filtration—including capturing particles as small as viruses—they are generally not appropriate for residential installation due to excessive airflow restriction. Only commercial applications, such as hospitals and clinics, with much higher system airflow can utilize a standard installation of MERV 13 to 16 filtration.

For informed answers about the MERV system of filter efficiency and how to achieve optimum indoor air quality, in the Bath, PA area contact the professionals at Sullivan Oil & Propane Air Conditioning at (610) 810-3992.

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