How to Choose the Right Furnace Air Filter | This Old House

Reviewing air-filter options with This Old House plumbing and heating expert Richard Trethewey.

Up in the loft, Richard showed Kevin why it's important to regularly change air filters in a forced-air HVAC system. Richard recommended making sure to get the right size and to select a "pleated" filter, which is better than a non-pleated one that you can see through. Richard also showed a "reusable" filter that can be cleaned and reinstalled. Finally, Richard showed an "electronic" air cleaner that causes dust to stick to plates that can be cleaned by rinsing with water.

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Homeowners have a virtual truckload of questions for us on smaller projects, and we're ready to answer. Ask This Old House solves the steady stream of home improvement problems faced by our viewers—and we make house calls! Ask This Old House features some familiar faces from This Old House, including Kevin O'Connor, general contractor Tom Silva, plumbing and heating expert Richard Trethewey, and landscape contractor Roger Cook.

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How to Choose the Right Furnace Air Filter | This Old House

[bigbeef]

Keep the cheap blue filter on standby for a really hot days or really cold day. max airflow. Then swap back to your Other filter when you can

[dvddmc]

been using a 1500 3M filter for years no issues change it every 2 months. and i have not been as sick as much and needed the extra protection since having pets in the house

[alowatsakima]

Replaced my big block store 1" filter with a high efficiency pleated filter. I selected a MERV 14 filter which filters allergens and pollen. The filter is 5" deep but fits in the normal 1" deep opening with the other 4" behind. . Keeps the house very clean

[fortunatedad]

I don't think furnace filters were made to clean the air for the house as much as for the furnace itself. If you go with too restrictive of a filter it doesn't take much to clog up then your furnace has to work so much harder, lessening the life of it.
Use a basic pleated and your fine. If you want cleaner air, get an air filtering system. IMO

[AGreedyTree]

My air conditioner can accommodate a 1" or 2" filter. After doing some research, I'm going to get a 2" filter with a lower MERV rating because I want better airflow. It looks like the previous homeowners were using the cheapest 1" pleated air filters. I took the cover off the evaporator coil and the coils were very clean.

[demetriosa]

Yes but most people’s heating duct work is not state of the art. So if u choose these high filtration filters you will essentially chock your furnace and cause it to run inefficiently and essentially shut it self off because of the high limit switch tripping due to air starvation across the heat exchanger. Cheap filter are probably the best filters to run as long as u change then monthly.

[kona]

Next on This Old House, how to repair your dishwasher after you washed your electrostatic unit.

[jimw]

Before using a high efficiency filter, check the differential pressure that your blower can produce. My furnace’s data tag says that the blower pressure is 0.2 in wc. More modern air handlers are 0.5 in wc. Even with a 4”, 8 merv filter, my unit was cutting out on high temperature according to my Nest thermostat. I only use the cheap filters now.

[francinecorry]

They don`t mention FPR (filter performance rating) or MERV( minimum efficiency reporting value) by the different manufacture`s.These two ratings are important when it comes to how hard your HVAC unit works .This incomplete but somewhat useful.

[sagapoetic]

This show is awesome. As a single female, I've learned so much -- thank you, TOH.

[onenikkione]

If you need filtered air in your house build a simple air filter using a box-fan, the filters of your choice, and tape (You Tube videos). Your furnace/AC needs to breath in order to function properly it can over-heat or freeze up and burn out the compressor as some of the higher rated MERV filters cause restriction of air flow.

[freewoodencrosses]

I just had a new HVAC system installed and they put a media filter just before the evaporator and they said to take out the 1-inch filter at the cold air return and don't have 2 filters. I disagree with this. I will be sucking dirty air into my ducts. Perhaps they also have a duct cleaning service to clean those dirty ducts. What do you think about that?

[bibo]

I have used a 13 Merv pleated filter for many years and have never had a problem. Just need to change it out as recommended, every 3 months or 720 hours of blower operation. You have to call the filter manufacturer to get the hourly change time. Most digital thermostats will tell you how many hours your system has run. It doesn’t matter if it is heating or cooling as regards to hours to change.

[oafyvonskidmark]

I have performeda Honeywell E nalysis on many homes and the high efficiency air filters greatly reduce the air flow, up to 1 Ton of air flow, 500 cfm.
I have seen pleated filters that when dirty really slow the airflow to the point the heater cant run over 5 minutes.
In AC mode, if your house is not cooling down it's the 1 Ton of airflow missing from your 3 ton system.
Use cheapies in AC mode!

[xDxSiCkNaStY]

the blue ones are actually better. Those fancy ones restrict airflow by a lot

[Kenster-man]

We have the standard/universal MERV ratings for filters - not sure why Home Depot (FPR) and 3M (MPR) had to come up with their own rating system.

[kman]

What is the airflow rating with those filters? Probably very restricted

[douglasgrant]

I needed to know which filter is specific for my Carrier electric furnace.. What MERVE rating is compatible for my furnace and so forth...They didn't get into that..

[hackprine]

Why does my furnace trip out on high limit with a pleated But it is ok with a fiberglass see through filter...

[malachy]

you would need a serious dish washer to clean that last filter.... but like many things  in the U.S. it's super sized compared to Europe...