Hesitant Handyman Repairs - The Furnace Air Filter...
Out of sight, out of mind…
When we first bought our house, there’s a lot of stuff I didn’t know I needed to know. Where’s my water shutoff valve? (Spoiler alert–I was running out to the street shutoff for four years before discovering the customer shutoff hidden in our garden–in my defense the previous owners buried it under a sheet of plastic and a copious amount of bark chips, and whoever installed it used what appeared to be a cheap irrigation shutoff instead of a sturdy ball valve, which is what I replaced it with when my neighbor noticed water pouring out of our side of the fence due to a break near the customer shutoff. Thankfully all those days running to the street shutoff paid off.) What do all of the circuit breakers in my breaker box control? But probably the easiest to overlook is the air filter for the furnace.
What is an air filter for, anyway?
If you’re a first time homeowner, you may not even know what the air filter is or why it needs to be changed. The shortest, most non-technical explanation is that it cleans the air. If you have a central air/heating system, your airflow is basically a big loop–air is sucked into the air return (in my house, this is where the filter is located) to the air handler, where the air is heated/cooled and then pushed out to the household vents in the great circle of airflow. (Cue Elton John musical number! Just kidding–we don’t have the kind of budget for that) The filter basically catches all of the nastiness in the air so it doesn’t get pulled into the furnace and recycled into your newly warmed/cooled air.
Why do I need to change it, though?
As the filter catches stuff in the air on its way back to the exchanger, it starts to fill up with all of that grossness. The fuller the air filter, the harder the exchanger has to work to pull air through, and it will cause your HVAC system to wear out faster. Think of the amount of effort you have to exert when drinking iced tea through a straw vs. a triple thick milkshake through the same kind of straw–it’s sort of the same between a clean filter vs. a dirty filter.
So what do I need?
Really? Not much depending on how your system is set up. In my case, I just need the following:
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- A new air filter. This will be specific to your system as there are a TON of different sizes–just go look at the aisle with them in your local home improvement store. In my case, it’s a 20 x 24 filter. *
- Whatever tools your specific system requires. In my case, all I needed apart from the filter was a Phillips head screwdriver.
*As an aside, depending on where you buy your filters, you may see something about a rating, and depending on where you buy the filter, the rating system will be different. I’m not going to go all in and explain everything about them (really? It’s pretty boring to get into), and other places have done a better job explaining it. That said, you may see one of the following:
- MERV – Stands for Minimum Efficiency Reporting Value, not Merv Griffin of Wheel of Fortune fame. Scale runs from 1-20, with 1 catching the largest particles and 20 catching the smallest particles. This scale is the industry standard scale used by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) to rate the effectiveness of air filters.
- MPR – Stands for Microparticle Performance Rating. This is a standard developed by 3M that only rates the filter’s ability to capture the smallest particle sizes. Ratings run from 100 all the way up to 2800, with 14 different options on the chart.
- FPR – Stands for Filter Performance rating. This standard was developed by the Home Depot and has ratings of 4, 7, 9, and 10. The intent was to take the guess work out of buying filters for the average Joe wanting the best air filter, which I appreciate.
- REM – Stands for Rapid Eye Movement, as in sleep. Which isn’t a filter rating system but is probably what you’re doing after reading this section. Wake up, I promise that was as much as I’m covering.
While I appreciate that everyone has different reasons for wanting their own separate rating systems (FPR seems more geared more towards the homeowner but inexplicably uses four non-sequential numbers to rate filters when I think a simple 1-4 with 1 being the lowest quality and 4 being the highest quality would’ve been sufficient. And really 3M? You needed 14 different varieties of your Filtrete products?), I generally get my filters at the Home Depot and will purchase at minimum the 9 FPR filters. As best I can tell the closest MERV rating to that would be a MERV 13 rated filter or a MPR rating of somewhere between 1500-1900. Honestly, this is probably way more information than you’d need to replace your filter. Just buy the one you’re most comfortable with. This isn’t rocket science, literally any clean filter will work better than a clogged one.
Alright, so how do I do it?
Every system is going to be a little different–in my video, I show off how I changed the filter in my system, which is located in the ceiling with our cold air return. That said, the process is effectively locate the filter, remove the old filter, insert the new filter, with different hiccups for different system setups. In my case the process went like this:
1. Open the return vent
In my house, the return vent is where the filter is housed. Our return vent is basically a large box vent in the ceiling upstairs in the hallway, much larger than the individual room vents, with a hinge and two Phillips head latches holding it in place. I used the screwdriver to open the latches and let the door swing down.
2. Remove the old air filter
Look, this should be pretty self explanatory. That thing is nasty and needs to be pulled out. Stare in horror at all of the dead skin particles that your filter has captured trying to get into your furnace for a brief moment, then yank the sucker out and toss it.
3. Insert new air filter
Now that you’ve disposed of the veritable colony of dead skin and microbial grossness, put a clean one in its place. There usually is an arrow pointing the direction that the air flow should go, make sure that you put the arrow pointing into the vent and not towards the floor.
4. Close the vent
I don’t feel like I should have to tell you how to undo what you did in step one. You’re smarter than that. Instead, I’ll provide you with a bit of random trivia: Gerald Ford was the first US President to attend an NBA basketball game in 1974, when he attended the Portland Trailblazers vs. the Buffalo Braves. If you ever win Sports Jeopardy because of this blog post, feel free to send me a portion of your winnings in gratitude.
