Indoor Air Quality Questions and Answers

by Dave on August 22, 2009

by Matthew Peterson

An aspect of building and designing “green” structures that has not gotten enough attention is the health aspects of these buildings. Indoor Air Quality is paramount in providing the inhabitants clean air to breathe. Clean air is free from small particulates – dust, dander, and other allergy irritating air borne pollutants. How important is this? According to the U.S. Environmental Protection Agency indoor air is two to five times more polluted than outdoor air.

The primary way we can defend our homes against particulates is with the air filter that is installed in your HVAC (heating, ventilation, and air conditioning) system. There are several types of filters from fiberglass panel filters (which are as effective as not having a filter…kind of…) to high MERV rated HEPA Air Filters. MERV is a standard used to measure the overall efficiency of a filter and are used to rate the ability of an air conditioning filter to remove dust from the air as it passes through the filter. Higher MERV ratings mean fewer dust particles and other airborne contaminants pass through the filter.

Strictly speaking MERV-ese, when you are looking at the ratings of various filters remember the following numbers and what they mean. Anything below a MERV 5 is really not effective or efficient. MERV 5 to 8 rated filters are a better choice and these filters will collect particles as small as 3 microns. Filters with a MERV rating of 9 to 12 are used in commercial and industrial applications and will stop particles in the 1 to 3 micron range. These filters are a great choice for home owners who want the best dust control possible. Key to know when using filters with MERV 9 ratings and above it is important to clean or replace them when recommended by the manufacturer because they will have a negative effect on air flow when they become dirty. This can lead to performance problems and decreased operating efficiency.

Let’s look into the most popular, most efficient types that will do a great job for your existing home or what you need to make sure is in your new home.

Pleated air filters are among them most popular types of filters available today – and with good reason. Most pleated air filters are rated at 20 – 30 percent efficient and have a MERV 5 rating. This of course depends on the material being used in the construction of the filter. There are pleated air filters with a MERV 12 rating which means it is over 97 percent efficient. This is a very high rating for a pleated filter. They are able to attain this very high rating by incorporating electrostatic characteristics in the pleated design. Another factor that makes some of these filters appealing is they don’t support the bacterial, fungal and mold growth.

Electrostatic air filters are a combination of mechanical air filtration and the technology used in many of the air cleaners commonly sold today which remove dust particles from the air by using static electricity or electronic means. The best furnace filter is the one that has the least effect on air flow but removes the most dust from the air. This is where the electrostatic furnace filter shines. Electrostatic air filters remove a very high percentage of contaminants from the air but at the same time have little effect on air flow. As air passes through electrostatic filters, a static charge is created within the filter; as a result dust particles are attracted to the filter and remain trapped there until the filter is washed.

HEPA air filters are among the most efficient air conditioner filters available – around 99%. HEPA is an acronym which stands for High Efficiency Particulate Arrestance. A HEPA filter has the potential to provide relief for allergy and asthma sufferers because they trap mold, pet dander, pollen, bacteria and many other airborne particles. Use of these filters requires that you be very diligent with the maintenance that is required to maintain them. This is important, to prevent problems that can arise from reduced air flow through an air conditioning system when they become dirty.

Fairly new to the market, because they typically are only sold to HVAC Wholesalers are Media Filters. Media filter capacity is very high compared to some of the other filter types available because they utilize all of the material in the filter. If dust is not stopped by the first part of the filter it will be stopped as it gets deeper into the filter. The easiest way to purchase these is through some online stores. When it comes to efficiency and cost, these are probably among the best available to home owners. The big advantage of these filters over electrostatic air filters is they do not have to be rinsed clean every few months, just change the filter pad and reinstall the frame with a new pad.

When it comes to combating all those things that float in our air and that we breathe in, look into upgrading your filters with one of those listed above. It may take a few minutes at your local hardware store to look through them and figure out which one works best for you but the benefits will pay off almost immediately. As a side benefit, for those of you that hate to dust (like me…), is that the less “stuff” in the air – the less “stuff” on your coffee table. Ah, the benefits of “green”.

Matthew Peterson is the Principal of Element Design Group in Lewes.

This column first appeared in Coastal Sussex Weekly, June 25, 2009.

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