Home Air Filters

ThankYouJack · Post by **ThankYouJack** » Sun Apr 05, 2015 8:30 am

How often do you replace them and where do you get them? I've heard that you're suppose to replace them every three months. My house has 4 of them, so if I pay $15 / each that would be $240 / year.

Hypersion · Post by **Hypersion** » Sun Apr 05, 2015 8:41 am

I have allergies so I change my every 3 months and buy the highest rated. If I didn't have allergies then I would probably just buy the cheap kind and changed it every 6 months.

tim1999 · Post by **tim1999** » Sun Apr 05, 2015 9:28 am

I check it every 30 days and usually change it every 90 days. I get them from Home Depot. They have "Good, Better, Best, and Premium" versions. I usually get the "Best" version. Around $20 or something like that. I only have 1.

wander · Post by **wander** » Sun Apr 05, 2015 9:32 am

I use permanent filter and vacuum/wash it monthly.

tomd37 · Post by **tomd37** » Sun Apr 05, 2015 10:02 am

I use the 20 x 25 x 1 inch 3M Filtrete Allergen Defense 1000/1085 MPR filter sold at Lowes or Home Depot locally. I have been cautioned by my HVAC company to consider not going to a higher level filter because it tends to reduce the air flow which can impact the proper operation of my HVAC units and place an undue strain on them. I personally opt to change the filter every two months instead of every three as 3M recommends.

I have a Skuttle humidifier unit attached to my first floor heating system which injects a mist of water into the duct heated air when the system is operating. For the last two or three years we have noticed a very fine layer of white dust throughout the house, almost like a fine talc, once the system has been operating during the winter months. I have determined through the non-use of the system this winter that it is a product of the mineralization of the water. Once the humidifier was shut off the talc like dust was non existent. Now we have lower humidity levels in the home but we do not have that very fine talc dust either. I hate to think how much of it has been deposited on and into the fabrics on the furniture and draperies.

For those of you who are active or retired military both Lowes and Home Depot offer a 10% discount upon presentation of a military id card. Also Lowes sells my filters in packages of two at a lower price and if you buy at least two packages of two at a time you can get another $3 off the price.

tibbitts · Post by **tibbitts** » Sun Apr 05, 2015 10:07 am

ThankYouJack wrote:How often do you replace them and where do you get them? I've heard that you're suppose to replace them every three months. My house has 4 of them, so if I pay $15 / each that would be $240 / year.

You've heard? If you haven't been replacing your filters, ever, how is it possible your hvac is still working?

You can't make general statements because it depends how much you use your hvac. Some people run hvac 24/7 (maybe fan-only part of time.) Some run hvac only occasionally. So it could be every month, or every year.

Our hvac can use 1" or 2" filters. I used to use a 1" washable filter, but now I think the 2" pleated paper filters do a better job (and no washing hassles.) I use about 4 filters a year at about $10 each. I've usually used MERV 8 (about MPR 600?), but have a box of MERV 7 I'm using now. I'll probably go back to MERV 8, because the color of the media for MERV 8 on the brand I buy makes it easier to judge the level of dirt on the 8.

How is your hvac designed such that you need 4 filters (in a residence?) Are you filtering the same air at multiple points? Obviously some huge houses do need 4 or more filters, but I'm guessing those homeowners have a lot more expensive issues than paying $240/year for filters.

ThankYouJack · Post by **ThankYouJack** » Sun Apr 05, 2015 10:16 am

tibbitts wrote:
ThankYouJack wrote:How often do you replace them and where do you get them? I've heard that you're suppose to replace them every three months. My house has 4 of them, so if I pay $15 / each that would be $240 / year.
You've heard? If you haven't been replacing your filters, ever, how is it possible your hvac is still working?

I replace my filters -- probably every 4-6 months. I may replace more frequently, but my HVAC is still working and I'm still alive

tibbitts wrote: How is your hvac designed such that you need 4 filters (in a residence?) Are you filtering the same air at multiple points? Obviously some huge houses do need 4 or more filters, but I'm guessing those homeowners have a lot more expensive issues than paying $240/year for filters.

2 on first floor, two on 2nd floor. 2,500 sqft house

tibbitts · Post by **tibbitts** » Sun Apr 05, 2015 10:30 am

ThankYouJack wrote:
tibbitts wrote:
ThankYouJack wrote:How often do you replace them and where do you get them? I've heard that you're suppose to replace them every three months. My house has 4 of them, so if I pay $15 / each that would be $240 / year.
You've heard? If you haven't been replacing your filters, ever, how is it possible your hvac is still working?
I replace my filters -- probably every 4-6 months. I may replace more frequently, but my HVAC is still working and I'm still alive

tibbitts wrote: How is your hvac designed such that you need 4 filters (in a residence?) Are you filtering the same air at multiple points? Obviously some huge houses do need 4 or more filters, but I'm guessing those homeowners have a lot more expensive issues than paying $240/year for filters.
2 on first floor, two on 2nd floor. 2,500 sqft house

So maybe it's filtering the air on two intakes for each unit I guess. My house only has one intake, directly attached to the hvac, so the filtering happens at the hvac unit itself. On my unit I can usually hear a difference when the filter starts getting plugged, because it gets sucked harder into the intake frame during startup. It would be nice if it was perfectly sealed but it's not. On my old washable filter frame I had put rubber around the frame to force it to fit more tightly, but I don't bother do that with the paper filters, since nobody else seems to do that, either.

123 · Post by **123** » Sun Apr 05, 2015 11:46 am

We have a furnace only, don't need AC in our location. We replace the filter every 2 or 3 months from November thru April. A replacement filter in May or June will be fine until late fall due to low use during those months.

Globalviewer58 · Post by **Globalviewer58** » Sun Apr 05, 2015 11:48 am

WalMart has NaturalAire washable reusable air filter $3.88 for a 20" x 30" Cut to Fit size. Have used same filter for several years and wash it 2x per year. This is a good filter for high air flow and high dust holding capacity.

ThankYouJack · Post by **ThankYouJack** » Sun Apr 05, 2015 12:00 pm

These permanent ones look good - http://www.amazon.com/16x20x1-Lifetime- ... +Permanent

Washing them seems quite simple (with a hose or in shower). They get great reviews -- although there's just a few reviews so it could be shill.

Has anyone tried them? I'll probably pick some up

Globalviewer58 wrote:WalMart has NaturalAire washable reusable air filter $3.88 for a 20" x 30" Cut to Fit size. Have used same filter for several years and wash it 2x per year. This is a good filter for high air flow and high dust holding capacity.

Do you have a link? The ones I saw were $20 and looked pretty cheaply made.

Globalviewer58 · Post by **Globalviewer58** » Sun Apr 05, 2015 12:18 pm

the product is shown as Natural Aire Hogs Hair Cut-To-Fit Filter.

Website link http://www.walmart.com/ip/16225736?www= ... irect=true

Think I am on year 5 with this filter. Still works fine.

tibbitts · Post by **tibbitts** » Sun Apr 05, 2015 12:22 pm

My two re-usable filters looked similar to these. Maybe if you have a pressure washer they're easy to wash; for me with just a hose, I never got all the clumped dirt (it wasn't clumped until washing, of course) out of the filter.

bac573 · Post by **bac573** » Sun Apr 05, 2015 12:24 pm

I change ours every six months, end of June and December. Usually buy a Honeywell 2-pack, 20x16x4, Merv 8. Our house is three years old, one story, 2200 sq ft.

Globalviewer58 · Post by **Globalviewer58** » Sun Apr 05, 2015 12:31 pm

Definitely do not recommend using a pressure washer to clean an air filter. For the Natural Aire reusable filter douse with water in utility sink or spray with hose outdoors. The dust balls up when wet. After the filter dries, brush the dust balls off into the garbage can. Then install the clean filter in the air return. Pretty simple to use.

ausmatt · Post by **ausmatt** » Sun Apr 05, 2015 1:00 pm

I replace every 3 months (for allergen reasons) using a MERV 13 rated filter. I usually order online from Amazon due to a slightly irregular size that makes it hard to find a high MERV rated one that's not $40.

stickman731 · Post by **stickman731** » Sun Apr 05, 2015 1:18 pm

tomd37 wrote:I use the 20 x 25 x 1 inch 3M Filtrete Allergen Defense 1000/1085 MPR filter sold at Lowes or Home Depot locally. I have been cautioned by my HVAC company to consider not going to a higher level filter because it tends to reduce the air flow which can impact the proper operation of my HVAC units and place an undue strain on them. I personally opt to change the filter every two months instead of every three as 3M recommends.

My HVAC guy also told me the same. He also told me less air flow - more dust in the house since it is not removed. I actually signed up on the Filtrete website (http://www.filtrete.com/wps/portal/3M/e ... ltrete.com) and get alerts and coupons.

livesoft · Post by **livesoft** » Sun Apr 05, 2015 1:26 pm

I bought permanent BoAir filters when I found out our size is unusual, not usually in stock at store, and cost $10 a dispo filter instead of $0.47 like all the other filters. I wash them when they are visibly dirty.

While the BoAir web site has info on cleaning, these things are indestructible, so using a pressure washer, hose, brush, even carpet vacuum cleaner with rotating carpet brush all work.

linenfort · Post by **linenfort** » Sun Apr 05, 2015 1:44 pm

Wow, never saw permanent furnace filters before, although I bought a metal disc coffee filter for my Aeropress back when I was using that method, and it worked great.
I replace filters once every three months with the blue or purple 3M Filtrete line for $18. The last time I was in, my local hardware store had changed brands, and it ended up being closer to $10 for something similar. Still, if these permanent filters work, they could save me a ton of money.

ThankYouJack wrote:These permanent ones look good - http://www.amazon.com/16x20x1-Lifetime- ... +Permanent

Washing them seems quite simple (with a hose or in shower). They get great reviews -- although there's just a few reviews so it could be shill.

Has anyone tried them? I'll probably pick some up

ddurrett896 · Post by **ddurrett896** » Sun Apr 05, 2015 1:52 pm

I buy cheap Flanders fiberglass filters that I change every 30 days. DONT BUY EXPENSIVE FILTERS!

I have a few buddies that do HVAC and they all use cheap fiberglass filers. The others restrict air and put more strain on the unit, wearing them down faster.

dolphinsaremammals · Post by **dolphinsaremammals** » Sun Apr 05, 2015 2:24 pm

New one of these at the start of AC season Filtrete Elite 2200 Filter. They're only in the AC, not the heating system.

ThankYouJack · Post by **ThankYouJack** » Sun Apr 05, 2015 6:37 pm

ddurrett896 wrote:I buy cheap Flanders fiberglass filters that I change every 30 days. DONT BUY EXPENSIVE FILTERS!

I have a few buddies that do HVAC and they all use cheap fiberglass filers. The others restrict air and put more strain on the unit, wearing them down faster.

Have you ever tried the cut to fit ones - http://www.walmart.com/ip/Flanders-5035 ... h/37922104

I may do that. I could switch them out each month and it would cost me less than $50/year compared to $240

FrugalInvestor · Post by **FrugalInvestor** » Sun Apr 05, 2015 7:03 pm

Our air conditioner runs almost continuously in the hottest summer months so I change my filters every month. It seldom runs in the spring or fall so I don't change them at all during that time period. My heat runs occasionally in the winter so I change the filters every couple of months then.

Filters with very high (smallest particle) ratings can be hard on your system because they restrict airflow. This can cause your blower to be overworked and prematurely fail. For that reason I use relatively inexpensive, more free-flowing filters.

mnvalue · Post by **mnvalue** » Sun Apr 05, 2015 7:19 pm

Here's where to get furnace filters: http://4qualityair.com/dustlok-c-24.html (use coupon code "REORDER" to save more money). These things have no paper edge, so air can't slip by, and they can't be crushed, bent, or otherwise damaged by "normal" mishandling in shipping or installation. The filter media gets thicker in the direction of the airflow, so they depth-load. That is, dust can pile up throughout the depth of the filter, rather than just on the surface. This allows them to hold more dust and thus last longer. I replace them after about 3-4 months of 100% furnace fan run time. When I'm not running the fan 100% of the time, they last longer.

Unless you're explicitly looking for a MERV 11 - 13 filter (which only makes sense if your system uses the 4" or 5" thick filters so they don't restrict airflow), the Dust-Lok is really the Last Word in filters. These are originally targeted at industrial/commercial applications, but they are great for residential as well.

If you have odd requirements, like (in my case) a dehumidifier or air exchanger, they can sell you custom-sized pre-cut Dust-Lok filters. Custom sizes won't have the internal wire-frame, though. They're just cut off a roll of material.

ThankYouJack · Post by **ThankYouJack** » Sun Apr 05, 2015 8:07 pm

I wound up picking up 24 of these for $50 - http://www.amazon.com/gp/aw/d/B005HN305 ... SY200_QL40

I figure I'll try them out for 6 months but then may consider the permanent filters.

6miths · Post by **6miths** » Sun Apr 05, 2015 8:24 pm

Rarely change the filters. Maybe once every year or 18 months. I don't wear a mask when I go outside either. Call me crazy!

topper1296 · Post by **topper1296** » Sun Apr 05, 2015 9:06 pm

I change mine every 4 months with one of the "lower" grade 3M filters.

Robert44 · Post by **Robert44** » Sun Apr 05, 2015 9:21 pm

Change them every 3 months with the highest allergy level model. Around $20 at Home Depot.

scottyja · Post by **scottyja** » Mon Apr 06, 2015 12:12 pm

When we had our furnace replaced we had a whole-house air purifier installed at the same time. It's a large cabinet that sits right next to the furnace, filtering everything coming from the returns. I replace the MERV-13 filter once a year for about $40. This has been so much better than dealing with individual filters every 1-3 months.

BW1985 · Post by **BW1985** » Tue Apr 07, 2015 2:33 pm

I just found out that this had to be changed.. I've been in my rental home 2 years and who knows the last time it was changed before I moved in.

When I went to replace the old filter it had collapsed and extremely dirty as you'd expect, so basically it was running without a filter for years...

abuss368 · Post by **abuss368** » Tue Apr 07, 2015 2:42 pm

We used to use one all the time. We disposed of it after many years.

BW1985 · Post by **BW1985** » Tue Apr 07, 2015 3:16 pm

mnvalue wrote:Here's where to get furnace filters: http://4qualityair.com/dustlok-c-24.html (use coupon code "REORDER" to save more money). These things have no paper edge, so air can't slip by, and they can't be crushed, bent, or otherwise damaged by "normal" mishandling in shipping or installation. The filter media gets thicker in the direction of the airflow, so they depth-load. That is, dust can pile up throughout the depth of the filter, rather than just on the surface. This allows them to hold more dust and thus last longer. I replace them after about 3-4 months of 100% furnace fan run time. When I'm not running the fan 100% of the time, they last longer.

Unless you're explicitly looking for a MERV 11 - 13 filter (which only makes sense if your system uses the 4" or 5" thick filters so they don't restrict airflow), the Dust-Lok is really the Last Word in filters. These are originally targeted at industrial/commercial applications, but they are great for residential as well.

If you have odd requirements, like (in my case) a dehumidifier or air exchanger, they can sell you custom-sized pre-cut Dust-Lok filters. Custom sizes won't have the internal wire-frame, though. They're just cut off a roll of material.

They don't show the thickness, are they all 1"?

bestyears · Post by **bestyears** » Tue Apr 07, 2015 4:49 pm

ddurrett896 » Sun Apr 05, 2015 1:52 pm
I buy cheap Flanders fiberglass filters that I change every 30 days. DONT BUY EXPENSIVE FILTERS!

I have a few buddies that do HVAC and they all use cheap fiberglass filers. The others restrict air and put more strain on the unit, wearing them down faster.

I agree with Ddurrett896. I work with a few HVAC contractors in Arizona and they personally buy the cheapest ones and replace them monthly. The so called "good, better, best" filters are not recommended. This is one time where you don't get what you pay for. Buy cheap and replace often.

bhsince87 · Post by **bhsince87** » Tue Apr 07, 2015 6:09 pm

The air filter serves two main purposes. First, it protects the HVAC unit itself from larger dust particles, lint, hair, etc. And second, it helps limit dust build up in the duct system.

As a filter gets dirty, it can actually perform these tasks BETTER! However, the reduced airflow can result in loss of efficiency, and increased wear on the system. So from that perspective, skimping on filter changes can be a false economy.

Filters can also be used to increase human comfort and reduce dust in the house. That's where the more expensive filters come in. Just keep in mind that this extra cleaning isn't necessarily "free". They might raise energy bills and/or reduce the life of the HVAC system.

mnvalue · Post by **mnvalue** » Sat Apr 11, 2015 11:26 am

BW1985 wrote:
mnvalue wrote:Here's where to get furnace filters: http://4qualityair.com/dustlok-c-24.html (use coupon code "REORDER" to save more money).
They don't show the thickness, are they all 1"?

Yes, the Dust-Lok filters are (nominal) 1". If you have something larger, they can still work. For example, I have a Trion Air Bear filter box that normally takes 4" filters, but there's no problem sticking a 1" Dust-Lok in there, since they don't impede airflow very much. If you want 4" or 5" filters, though, the same place sells them in types other than Dust-Lok.

midareff · Post by **midareff** » Sat Apr 11, 2015 12:45 pm

ThankYouJack wrote:How often do you replace them and where do you get them? I've heard that you're suppose to replace them every three months. My house has 4 of them, so if I pay $15 / each that would be $240 / year.

My condo takes four as well, which is overkill for 1400 SF. I use Filtrete 1000's and change every 3 to 4+ months depending on season. Closer to three in the summer, longer in the winter months. I use an online supplier with a discount over local pricing and free shipping for half cases.

abuss368 · Post by **abuss368** » Sat Apr 11, 2015 12:57 pm

Do any Bogleheads believe that home air filters help with seasonal allergies?

ThankYouJack · Post by **ThankYouJack** » Wed Apr 22, 2015 11:36 am

I was just looking through the manual of my new thermostat - http://www.amazon.com/Lux-TX9600TS-Univ ... B0044UYVFW

It has a Change Air Filter setting that is based on run-time not days. I'm sure some homes are dustier than others, but kind of a neat feature that I'll use.

NOTE: Air filters are sold based upon how many days they are rated for. One
day of filter run time is actually considered only 8 hours (not a full 24, since
your heating and/or cooling system only runs for approximatly one third of
the time). For a “90-day” filter, use a limit setting of 720 hours should be
used, and for a “30-day” filter, a limit setting of 240 should be used.

gnosis · Post by **gnosis** » Wed Apr 22, 2015 11:46 am

I have found that eBay has hands down the best price for air filters. I buy Merv 8 in 6 packs for about $30 and change them every 3 months.

Go Blue 99 · Post by **Go Blue 99** » Wed Apr 22, 2015 11:55 am

I typically buy filters when I see sales posted on Slickdeals.net.

We don't change them as often as we should though. The builder didn't do a great job of installing the HVAC unit in the attic, and there is some dried plaster/concrete-looking thing that makes it very difficult to pull out the existing filter. We have to use a steel hanger to jimmy it out. My wife and I despise when it's time to replace it.

Epsilon Delta · Post by **Epsilon Delta** » Wed Apr 22, 2015 12:21 pm

tibbitts wrote:You can't make general statements because it depends how much you use your hvac. Some people run hvac 24/7 (maybe fan-only part of time.) Some run hvac only occasionally. So it could be every month, or every year.

And some people have dogs, or wood shops, or do things that generate dust.

brucesprings · Post by **brucesprings** » Wed Apr 22, 2015 1:03 pm

[quote="ddurrett896"]I buy cheap Flanders fiberglass filters that I change every 30 days. DONT BUY EXPENSIVE FILTERS!

I have a few buddies that do HVAC and they all use cheap fiberglass filers. The others restrict air and put more strain on the unit, wearing them down faster.

I heard the same from a couple different HVAC guys also. I buy the cheap ones from Menards for a buck each.

nominalBob · Post by **nominalBob** » Wed Apr 22, 2015 4:26 pm

A clogged filter can actually place less strain on a blower. When blocked, the speed of a squirrel cage blower goes up and the real electrical power drops.

4nursebee · Post by **4nursebee** » Wed Apr 22, 2015 4:41 pm

I used to buy the best filters.
My AC guy said not to, now I buy the cheapest.
I change them when I think to see if they are dirty.

wfrobinette · Post by **wfrobinette** » Thu Apr 23, 2015 8:14 am

ausmatt wrote:I replace every 3 months (for allergen reasons) using a MERV 13 rated filter. I usually order online from Amazon due to a slightly irregular size that makes it hard to find a high MERV rated one that's not $40.

+1 The off brand filters are much cheaper than 3M and the like and work just as well. I replace every 2 to 3 months.

anoop · Post by **anoop** » Sun May 12, 2019 1:07 pm

(Resurrecting an old thread because I have a couple of related questions.)

I have been using Filtrete 1900 and replace after 2.5-3 months. They do look very dirty by then compared to a new one. Should I be replacing them sooner?

Filtrete also makes a smart air filter that pairs with a smartphone and tells you exactly when it needs replacement. Has any used those? If so, is something you would recommend?

In general I am averse to anything smart, but if this comes strongly recommended, I may give it a shot.

andypanda · Post by **andypanda** » Mon May 13, 2019 7:34 am

"I have a few buddies that do HVAC and they all use cheap fiberglass filers. The others restrict air and put more strain on the unit, wearing them down faster."

I agree, unless your system was built to use a 5" thick high MERV filter or something similar. The professionals I spoke to had a particular dislike for the Filtrete brand 1" filters.

The purpose of an HVAC filter is to filter the air going through the HVAC system so the blower doesn't clog up. It's not to clean the air you breathe. That's what a vacuum cleaner is for.

I didn't know any of this until the HVAC folks clued me in on the secret when we got bids and had Lennox install a modulating heat pump and air handler and new galvanized steel ducts. Don't choke off the air to the system with improper filtering.

It's your equipment, use it the way you like, but it can take more electricity to run an air-starved system and it will work harder and may break sooner.

A440 · Post by **A440** » Mon May 13, 2019 8:52 am

ddurrett896 wrote: ↑Sun Apr 05, 2015 1:52 pm I buy cheap Flanders fiberglass filters that I change every 30 days. DONT BUY EXPENSIVE FILTERS!

I have a few buddies that do HVAC and they all use cheap fiberglass filers. The others restrict air and put more strain on the unit, wearing them down faster.

+1 I have Alexa remind me to change them

stoptothink · Post by **stoptothink** » Mon May 13, 2019 8:53 am

I buy the cheapy "1 month" filters from Amazon. The previous owner said he noticed a nearly 10% decrease in heating/cooling costs by using the cheaper filters. They say 1-month and I check them at least that often, but we very rarely use heat/ac so they usually last several times that long. They hardly look dirty at all when I replace them. I think I bought a 12-pack over 2yrs ago and we still have a few left.

anoop · Post by **anoop** » Mon May 13, 2019 9:56 am

andypanda wrote: ↑Mon May 13, 2019 7:34 am "I have a few buddies that do HVAC and they all use cheap fiberglass filers. The others restrict air and put more strain on the unit, wearing them down faster."

I agree, unless your system was built to use a 5" thick high MERV filter or something similar. The professionals I spoke to had a particular dislike for the Filtrete brand 1" filters.

Consumer reports rates them very highly. Would they not have pointed out this issue if there was any merit to it?

This is what CR says for the Filtrete 1900 1" filter:

Better than most at removing dust, smoke, and pollen at its lowest speed, which matters if you have a two speed furnace or central AC air handler. Especially effective at removing dust, smoke, and pollen at its highest speed, important if you have a single speed air handler. Filters dust, smoke, and pollen with little noticeable restriction of airflow through the forced-air heating/cooling system.

The only con listed is price.

stoptothink wrote: ↑Mon May 13, 2019 8:53 am They hardly look dirty at all when I replace them.

Could it be that it is not very effective at filtering?