Seattle Home Inspector's Blog


One can buy a thousands filters for the cost of a new furnace.

There are tons of simple maintenance items around the home that if neglected will cost more to fix than it would if they were regularly maintained.

I am not talking about big maintenance items like keeping the house painted or the roof repaired etc.  I am talking about the really simple stuff like changing the furnace filter regularly.

Plugged furnace filter

There is no set rule as to how often the furnace filter needs to be changed.  It will vary due to lots of factors---all related to how much the heating and/or cooling system is used and how much crud is in the air.  People that have pets or live next door to lint factories will likely need to change their filters more often.

As a general rule I tell clients to change them at least every 6 months at first.  If they are still really dirty after that time frame, change them more frequently.  If they are not dirty at all, try stretching out the time period until you find what works for your particular life style.

I got thinking about all this due to a maintenance sticker I saw on the side of a furnace the other day.  It had two notes indicating that the service technician changed the filter.  In the first instance the recorded that they advised the tenant as to how to change the filter.  In the later instance it appeared as if the service call was entirely related to changing the filter.  Now that would be an expensive way to maintain the filter.

Change your furnace filter

Changing the filter is a very easy thing to do, and every homeowner should take this on if they don’t want the high cost of the service technician to do it.   Damage to the furnace heat exchanger can occur as a result of clogged filters, so not waiting until the service technician is there to do it is considered prudent.

One can buy thousands of filters for the cost of a new furnace.


Charles Buell, Seattle Home Inspector


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Comment balloon 28 commentsCharles Buell • March 29 2011 10:58AM


I always enjoy your posts...Charles thank you for sharing. As to changing a filter, even an all thumbs person like me can do it....

Posted by Richie Alan Naggar, agent & author (people first...then business Ran Right Realty ) over 7 years ago

Something I learned from a good HVAC guy - He said to forget the expensive hepa type filters for the air return as they have a tendancy ristrict air flow and work the blower motor harder than it shoud work. Motors cost much more than filiters so he recommended changing regular cheaper filters more often. Makes sense.

Posted by Randy Landis, Overseas Retirement Consultant (Retired in Samar) over 7 years ago

I agree! Change them often to help maintain the furnace and all it's parts. By not changing the filter, you make the blower work harder which in turn, wears it out sooner and not to mention how much cleaner the air in the home will be.

Posted by Michele Hansen, Realtor, ABR (Bangerter Brothers Realty) over 7 years ago

Hmm, that reminds me, I need to change mine!  (I'm not as bad as the picture!!)

Posted by Gerard Gilbers, Your Marketing Master (Higher Authority Markeing) over 7 years ago

Setting up a reoccurring reminder on your calendars is a good practice. Otherwise its out of sight and out of mind.

Posted by Robert Butler, Montreal Home Inspector | Aspect Inspection (Aspect Inspection) over 7 years ago

So simple yet, so easy to forget! Great reminder! Thank you Charles!

Posted by Lydie Ouellet Dickinson, Realtor (Realty Executives Tri County, Bellingham MA) over 7 years ago

GOOD MORNING CHARLES!  Dirty filters cost in so many ways.  It's just much much cheaper to change them out and really, it doesn't take that long to do!

Posted by Gabrielle Kamahele Rhind, Broker/Owner (KGC Properties LLC, Tucson Property Management & Real Estate) over 7 years ago

Richie, thanks---always good to have you stop by

Randy, there are a couple of things I want to address regarding your comment.  The expensive HEPA filters are very good and do a way better job and are worth it for that reason---they may need to be changed more often though.  Regardless of what type you use, they have to be changed often enough to allow for proper air flow.  Which brings me to the second thing I want to talk about.  It is actually "urban legend" that the furnace blower will work harder with clogged filters.  The blower will actually work less hard and actually take less electricity to run the thing than it would if it was actually doing work---moving air.  With no air flow it will just sit there and spin freely.  What it is hard on is the heat exchanger because adequate air flow is not being maintained.

Michele, see my comment to Randy

Gerard, I would hope that no agent is bad at changing their filters---they hear it enough from inspectors :)

Robert, yes---good idea

Lydie, you are welcome

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 7 years ago

Gabrielle, yes---it only takes seconds usually

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 7 years ago

Thats the key point Charles, its the heat exchanger thats at risk not the blower.

Posted by Robert Butler, Montreal Home Inspector | Aspect Inspection (Aspect Inspection) over 7 years ago

We have a beach house and were not there while it was rented out (obviously). The air filter clogged, because no one ever changed it,  and it ended up costing us big bucks on service calls and repairs.  Now we have a maintenance program in place.

Posted by Holly Weatherwax, A Great Real Estate Experience ( Associate Broker, Momentum Realty) over 7 years ago

Like Gerard above, I'm thinking I might need to go and check ours.... soon!

Posted by Brenda Whitman, Live in Laramie Real Estate, Broker/Co-Owner, Laramie, Wyoming (Live in Laramie Real Estate, Laramie, Wyoming) over 7 years ago

Charles, I like that idea of a service log on the unit.  Wow!

And I chuckled a little at the idea of a lint factory.  Somehow those places get their product in my jeans pockets every week.  How do they do that?!

Posted by Jeremy Wrenn, C.O.O., Winslow Homes (Winslow Homes) over 7 years ago

Reading the service history sticker, clearly some habits are hard to break!

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) over 7 years ago

Robert is amazing how often I hear this about wear on the blower---I used to think the same thing myself until I played myth busters and replaced my own filter with a piece of plywood and then tested the amerage on the blower (not for very long though :)

Holly, good to have a schedule

Brenda---almost anyone can change these things

Jeremy it is just one of those great mysteries

Jay, it seemed so :)


Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 7 years ago

They probably call the service guy when the air flow is so low they can't feel the heat.

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) over 7 years ago


Just remove he darn thing and let it blow ; )

Posted by Donald Hester, NCW Home Inspections, LLC (NCW Home Inspections, LLC) over 7 years ago

I had to stop by and say Hello since Craig Rutman awarded you the great sweater that I had a few wks ago....LOL...Nice to meet you!

Posted by Kristin Johnston - REALTOR®, Giving Back With Each Home Sold! (RE/MAX Realty Center ) over 7 years ago

It's amazing, simple things can save a lot.  Thanks for the information.

Posted by Kenneth Cole, NYS Licensed Real Estate Salesperson (Weichert Realtors Appleseed Group, 2043 Richmond Ave. S.I.N.Y. 10314. office phone 718-698-9797, -) over 7 years ago

Jim, it sure seems like it

Don, I find a surprising number that are doing just that

Kristin, it is an awesome sweater to get to wear---I have great company :)

Ken, for sure

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 7 years ago

Let alone how dusty your home gets... When I was renting out my first home the tenant called me and said the dryer was going out... When I came over to look, there was so much lint in it, it was like a brick! Ah, those little chores...

Posted by Rene Fabre, Marketing in the Digital Age (First American Title) over 7 years ago

Rene, they can actually get so much dirt in them that they actually become a really good filter :)

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 7 years ago

Mr Charles,

Speaking of dirt, I have let Mr Craig in on some of your secrets.


Posted by Steven L. Smith, Bellingham WA Home Inspector (King of the House Home Inspection, Inc.) over 7 years ago

Every six months?  Wow, you guys must not use your furnaces / air conditioners nearly as much in Seattle.  Around here every one to three months, at most, is the standard.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 7 years ago

Valerie---perhaps it was different tenants :)

Reuben, what is an air conditioner? :)  Seriously we don't run them as much as you guys for sure.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 7 years ago

I had my mother in law call me after she moved to the dusty wasteland of Moses Lake.  It was 110 degrees and her heat pump was working but not putting out much cold air.  Being the dutiful son in law, I made a weekend trip over the hill to take care of her list of repairs.

I turned on the heat pump and sure enough, cool air and not much of it was flowing at the floor registers.  I asked when she changed the fileter last.  "The what?"  The air filter.  "Whats that?"

I opened the access panel and pointed it out to her.  I attempted to remove it but it was "stuck".  I removed the upper panel and looked in.  Well it seems the previous owner.......with cats.... never changed it either.  There was 5 inches of layered dust and cat hair covering the filter.  I turned all the power off to the unit and spent the next hour pulling out bag after bag of gunk and then vacuumed the unit.  I went to the store, bought a 12 pack of filters and installed one with directions to change it every month when she made her house payment.

I turned the unit back on and the drapes started blowing, doors shut themselves and the place dropped from 95 degrees to 74 in a little under two hours.  Yep, change the filter.  I can't imagine how much money she has wasted in running the heating / cooling 24 hours a day.

As a reminder to all.  DO NOT use an electrostatic air filter if you have a heat pump or air conditioner.  They pick up too many impurities and will clog easily.  Your outside compressor will fail prematurely with clogged filters.

Posted by Stephen Stanczyk, Home Inspector - Puyallup WA (Safe Haven Home Inspections) over 7 years ago

Stephen, I would argue that regardless of the equipment on the systemy one will need to change/clearn the filter as often as necessary---since the real goal is to clean the air.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) over 7 years ago

Mr Charles,

I am pleased to have done my first ever pool inspection. Regarding this, I find my pressure is better when I drink green tea.


Posted by Steven L. Smith, Bellingham WA Home Inspector (King of the House Home Inspection, Inc.) over 7 years ago