Beware of High Efficiency Furnace Filters!

Throughout this site we’ve been informing you to make green choices and purchase high efficiency products. The term efficiency stems from the word “efficient” and Chambers Dictionary defines it as: producing satisfactory results with an economy of effort and a minimum of waste. You might be asking yourself what do furnace filters have to do with efficiency anyway? A furnace filter affects 5 to 15% of your total heating/cooling bill so one can see the importance of taking this seriously.
As a motorcycle fanatic I was appalled to find out what a high efficiency furnace filter was. The term high efficiency or high performance air filter in the motorcycle or automotive field means that you will increase power and decrease fuel consumption by installing one. A high performance air filter for these applications allow for more air flow to the engine while still keeping the debris out of the intake system. Why would I not want one of these for my heating system in my house? You absolutely do, but they are not considered efficient. In fact, unlike the high performance air filter which costs almost double what a standard one goes for; a low efficient furnace filter costs around a dollar. These would be the standard fiberglass pleated 1 inch filters. Usually blue in color.
The American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) came up with a standardized rating system, based on the European concept for heating/cooling system air filters. This is known as the MERV rating, or Minimum Efficiency Reporting Value. Whatever that means! The higher the MERV rating, the more efficient the air filter is. Their definition of efficient is the amount of airborne particles the filter removes. In other words, the higher the MERV rating, the more air flow restriction or pressure drop, the more cost, and the more wear and tear on your heating and cooling system.
Heating systems are designed to run at their highest temperature limits in order to meet their rated output. Most new heating systems are designed to run with all registers open, free of any airflow restrictions, and a clean, 1 inch standard air filter. Any deviation from any of these and the maximum operating temperature in the plenum or the heat exchanger will be exceeded. This causes cycling of the heating system which equals overheating shut down and restarting which drastically affects your bill…far more than 15%. If this persists for an extended length of time it will lead to damaged high limit (temp. %) switches, then ultimately a cracked heat exchanger requiring a complete new heating system.
There are many types and styles of air filters on the market today and unless you have asthma, where micro particles can cause you grief; a standard 1 inch low cost filter will suit you fine. If your respiratory issues are severe enough, you might want to consider an electrostatic air filtration system or a completely isolated HEPA filtration system that does not interfere with your current heating system.
Now that you are familiar with the MERV ratings and how a dirty air filter can reduce air flow and increase operating cost. Let’s try to use this information to make the right choices in trying to decrease how much fuel we actually need to heat and cool our homes. If you are unsure of the location of your furnace filter Northwest Natural can come to your home at no additional cost to help you locate your air filter for inspection.
Joe Curnes