My 2 cents on the box fan filter system. Although you can put it on the inlet side of the fan, what happens is as the filter starts to load up it will cause a low pressure on the back side of the blades and air will slip around the blades from the outlet side. I figured this out because my blades would still get dusty even though the filter was sealed on the back side. A better way is to take 2 20x25 filters and put them in a V shape on the outlet side of the fan. Use the cardboard box that the fan came in to cut out two V shaped covers for the top and bottom open sections. Tape all that to the outlet side then the air is forced to go through the filters. The reason you use two is because it gives you greater filter surface area and doesn’t put too much back pressure on the fan motor.

If you have humid air, don't forget a dehumidifier does a great job of catching & washing out dust on the cold coil.

I've been doing the box fan thing in my workshop for a couple years now. I buy 2" MERV 13 filters and run two fans in the shop. I also have a Dylos air quality monitor and in less than an hour, I can get both large and small micron sized particles down into the low teens or single digits, it really works great.

I have used the "emergency solution" before! I actually took apart my old furnace and plan to use the blower to make a shop filter!

Thanks for putting this information out to everyone. I work for an HVAC contractor in Northern California and I have an Aprilaire pleated filter on my home heating and air conditioning system. This year I added the Air Scrubber Advanced by Aerus and with both, my indoor air quality is outstanding during these poor air quality days.

After having 500 ppm air outside for a week and a massive wild fire a few miles away I’ve realized how important it is to build tight and have good filtration

I had an April Aire filter for our previous house, and it did a good job. Not only that, the filter was so big it only needed replacing about once every 18 months, and buying the paper filters and replacing them in the reusable box yourself made it fairly economical. When the fires started (we lived in CA then), we went up to a Pure Air from Lennox - the filter was slightly better (but smaller and more expensive, and needed replacing every year), but the UV was a big help getting rid of the smell of the smoke (which is not just from particles, but compounds formed during the burning) - the UV is supposed to kill virus and bacteria, but it also makes O3 which kills the smells somewhat (well, something did - the new filter did a better job with the smoke smell than the old one, and improved my wife's hay fever).

Here's a comment for the algorithm. Thanks for taking the time to create and post even short, informative videos like this. You and your channel are helping alot of people man, thanks for all you do.

I work as a Mechanical Engineer designing HVAC systems for commercial buildings, and have had lots of people ask us what they can do for filtration because of covid. Obviously increasing your MERV rating is always good but you have to be careful about it and know what all will happen when you increase filtration. First off, a better filter will create more back pressure on the blower motor. You can't just throw a HEPA grade filter into an existing system, the motor just won't be able to pull air through it. Second, better filters need to be changed more often. I tell friends and family this all the time and it doesn't seem to click. They think, "I paid more, this should last longer." That isn't the case. Your better filter is catching more stuff and smaller particles and is going to clog up much quicker. Even I sometimes forget that in my own house. I just a week ago had to change my filter that was about a month old because it was so clogged up it was affecting my A.C.'s ability to cool my house.

Thanks, Matt! I've forwarded your video to my relatives in WA and OR, some of whom have breathing difficulties even before the wildfires.

I have been using my HVAC system to keep my indoor air quality up by setting it to circulate the air. Had to change the filter a couple times but its well worth it.

Thanks Matt. I just share this video with my nephews in Portland.

Matt thanks for breaking this down, planning for a remodel on my house this vid has really helped me. Thank you .

Just installed "return grille" style filter. Allows 4-5" deep filter to be installed in a traditional 1" return grille. LOVE THEM!!

You want to know how to really keep your house free of smoke? Go stop at your local hydroponic shop, get a carbon filter and a fan, then grab some ducting and a flange. Put a hole in the board and attach the flange, then attach to window like a portable AC unit. duct to fan with ducting. Turn fan on, let the smoke filter through the carbon and pressurize your home. Keeps air from being sucked in because it's positive pressure and has been run through the carbon filter.

These are great options. Keeping up with current events👍. I really like the filtration example. Yes, the merv 13 is highly recommended👍👍👍

I bought the Conway recommended on the Wirecutter website a few months ago for another reason, and have been quite happy to have it during the fires. In addition to filtering, it also has an air quality sensor (and you can set it to adjust it's speed based on air quality).

It was ALREADY important to us at DUCTZ ! Thanks for sharing this Matt !

Thanks for the content. It's important. I'm using a Lasko Wind Machine ($40) pointed straight down and a 3M 20X20X1 Odor Reduction Filter. I think using this has likely saved me years of time on the planet. Stay Safe Matt and keep up the great content.

Great info. I brought in my hepa air scrubber I use for work. 1000 cfm. Cleaned the house out quick. Sucks that machines like this are so expensive but if you have one available it makes such a huge difference.

Thanks for the prayers, Matt. They're needed... :)

Wild fires aren’t just occurring in California; but are sadly burning in all three western most US states, include Oregon and Washington.

Definitely one of the few advantages to having a fully ducted heating/cooling system in your house. You can't upgrade the filter on a mini split or radiant heating. My parents had to leave their house in Oregon because the elderly dog couldn't breathe inside the house! And they have no way to filter the air with radiant heat.... I plan on deleting my central heat pump and putting in radiant heat and a few mini splits - but I will keep the duct work and blower so I can circulate and filter air when needed. I'd like to set it up so I can suck in air from outside or suck bad air from inside and put it out as needed.

Seen this all over social media. Already made one. I put weather stripping around the edges and cut the back out for better air flow. If anything it really does wonders for kitchen smoke lol. Hope it does well with smoke too. I live in washington, but my house isn't that bad, but outside is

I live in the Seattle area and I have a HVAC system with the larger filter as pointed in this video (not that model though). The HVAC has the feature of the continuous recirculation which I found out from friends not many do. I can say it has helped keep the air quality in the house to high level but as Matt pointed out, my older house leaks, so anytime an exhaust fan is turned on (bathrooms, etc) the smoke level increases in the house for a bit until the HVAC catches up.

Great video!

I made a box fan version. it does work. Just to be cautious of is that the higher rating filter will have more restriction, and box fans dont make good pressure. So CFM really drops a lot. I just use FPR 7 filter, and it does good job.

One should be careful about increasing the MERV rating on a whole house air cleaner. The drop in static pressure could cause a problem with the A coil not getting enough air and freezing up.

I live just south of Reno Nevada and the smoke here has been terrible. Air quality index has been pretty steady at about 150 and above. Some days are better but today was one of the worst days. 2 years ago I bought a Honeywell air purifier that's bigger than the one you showed and it is my Saving Grace. We have two of them in the house now. One of them is in my bedroom.

This is very useful coming from Oregon right now. Thanks. Also a suggest for another air flow vid: note that people using window air conditioners may be creating negative pressure and sucking the smoking air in. I did a test yesterday with a monitor I got. PM2.5 went up into the the 80's within minutes of turning the air conditioner on, then took a half hour or so for the air purifiers to get it back down to single digits after turning it off. The scary thing is it wasn't really perceptible, wouldn't realize it was that big a difference without looking at the monitor numbers.

You are the Davis family go to for build information!!! Thank you so much for your KZfaq content.

Thanks Matt for making this video im in vancouver bc .... our air is really bad... i will share this content to help others... huge fan keep up the good work!

Northern California here, we've already had our first big fire starting a month ago with the LNU Complex, at the closest it was a dozen miles away. We always keep a stock of N95 masks on hand because of previous fires (handy during social distancing too). At night I turn on a fan to draw cool air into my home office and every morning the office has a thin layer of ash on everything. I can't wait for the rain this year!

Matt, I’m not a MEP Engineer or an HVAC sub, but from what I’ve read/heard installing one of those whole house merv 16 filters on ur return air will greatly decrease the efficiency of ur HVAC system. U r basically making the unit work harder to pull air into the system. Thereby it will burn out quicker. So it’s a trade off on air quality.

On your recommendation I called Aprilaire and spoke with a tech rep to get more spec and shipping info. Now, I'm buying two room units from them. Oddly enough, the Amazon price for the same unit today (9/16/2020) was approximately double the price of the direct Aprilaire price. I like what I heard and that I could talk with someone here in the US. Also, Matt, I let them know that it was you who recommended them to me.

Glad to see you discuss air quality. There are also a lot of air quality monitors on the market that measure particles and VOC's. Check out the Glas smart thermostat by Johnson Controls.

Good Idea! Tell the news station!

This maybe a duplicate. I don't think my original posted. We have been using a 20 inch box fan with a 20" x 20" x 4" mrv 12 filter for the last week or so and hope it will continue to function as well for the next week. Hopefully by then the air quality will improve. It has collected a lot of smoke particals and is becoming very dark. The filter is on the exhaust side of the fan. The fan is on the middle speed.The air flow is good and the fan dosn't appear to be over heating. It has improved the comfort and air quality in our home greatly. The cats love it they sit in front of it one at a time. I'm glad I had a filter the chances of replacing it in the next few months appears to be slim to none.

Matt, Matt, Matt.... I have infinite respect and admiration for you and your videos. I always enjoy watching your videos. I always learn good things while watching your videos. Then this video comes along. Not up to your usual standards. - That “fog machine” test. Not really accurate or practical since most fog machines just produce water vapor. A bit of a difference from real smoke. A water-logged filter will behave differently. - The fan with the air filter attached, nice and economical .... I would have mentioned placing it as close to possible where air comes in - Advising against filters with UV lights?!?!?!?? No. Unacceptable. Clean air, free of germs, is priceless. You continue to build homes, but let doctors give medical advice regarding devices that use UV light to sanitize... until you see a video of surgeons showing how to frame a house. Lol. - That AprilAir purifier is a ridiculous behemoth.... now.... the fan inside occupies, at best, 1/3 the surface area of the filter. Not good. Inefficient use of such a large filter. I would be very curious to see that filter after 3 months of continuous use. - One aspect that was not covered in this video.... the noise from the room purifiers. Unfortunately, some people have such a low tolerance for noise generated by these filters. - Another aspect of purification not covered.... using the typical 20 x 20 x 1 type filter in central HVAC in apartments. The usual filters supplied by the landlords, have holes big enough to drop marbles through. Go the distance and get a good, high quality filter. I like the purple label 3M Filtrete filters. But if you install one of those, inform the landlord so they can inform the maintenance NOT to swap out your new $20 filter with a 25 cent filter provided by the landlord. - I use Germ Guardian purifiers. The same ones used in hospitals. They have several sizes of filters. Even ones that are just slightly larger than a nightlight. I cannot say enough good words about Germ Guardian devices. - CFM is not as important as purifying the air. 30 CFM of purified air is much more important than 60 CFM of dirty air. - Please keep in mind that there are people in older structures who watch your videos. An air tight home is just a dream for them. - Another aspect of room air purifiers... proximity. Keep the air purifiers relatively close to where people are.... not across the room in a corner... unless air is leaking in near that corner. - One serious omission... no mention of the estimated lifespan of each filter. Not good. Of the room purifiers you had there, do any of them notify when the filter needs to be replaced? My floor standing GermGuardian is not shy about sounding an alarm when the filter or UV light needs to be replaced. And those filters that get retrofitted to a furnace... we all know people will keep a 6 month filter in place for 5 years... out of sight, out of mind. Whether I like it or not, I have dealt with a healthy variety, and quality, of air purifiers over the past 15 years. This is due to loved ones with allergies and medical issues. You are right about HEPA. Go HEPA or you might as well through your money away. Thanks again. I look forward to your next video. P.S. The reason I started watching your videos about 3 years ago, was so that I could basically build a home from a patch of land. Why? Because in January 2018, at their request, I adopted two boys in the rural Philippines. I mean RURAL. Properly built houses there, are a luxury. They are more like Gilligan’s Island huts with corrugated metal roofs and bare minimal electrical wiring...in the form of extension cables. Don’t even think about indoor plumbing. When COVID-19 is finally just a painful memory, I will be moving there and building a home for my sons and there Mom, whom I will marry. I want to build them a quality home... a home that has real wiring, keeps out rain, bugs and critters. And maybe Tesla solar panels and power banks so they finally have reliable electricity. And maybe rain water harvesting. No shortage of rain there throughout the year. Your videos have been invaluable in my pursuit of learning to build a great home. Thank you for that. Oh yeah... my youngest son, 10 years old, will be painting his bedroom in a Spider-Man theme. Lol. I told him it is his room... he is in charge of it. His Mom was not thrilled, but she agreed to it. Lol.

I like the wall you have there.

I totally taped a filter to the back of a box fan years ago when my roommate's dog was bothering my allergies. My roommate thought it was embarrassing, Haha!

the cheap fan solution on the right is the best because you can buy some extremely good filters for cheap. If you buy the filters for the other solutions, you'll have to spend $100 for a filter vs $15 for the box fan.

Very cool idea to save money for us diys...............kids can learn from this big time....tnx,pat...land o' lakes,wi.

5:30 Matt's "hair of the dog" solution. :o) Excellent video, Matt, as always. I appreciate your consistent efforts over the years. I've learned so much from your channel.

box fan rig is great for getting sawdust out of the air in a wood shop.

Before putting a HEPA filter on your existing Central AC units, make sure you've enough fan to sustain that Pressure Drop. Chances are the fan that was design for your house only considered a mere MERV 11 filter for the system. If you replace that with a HEPA filter, that fan might not have enough static pressure to pull required flow because HEPA filtration creates additional restriction to the airflow. Worst case, the cooling coil will freeze because you are are the starving the system for airflow. That means less heat than it was being designed for and the coil freezes.

Apparently its hard to find furnace filters here on Seattle. This is probably going to happen every year so probably a good idea to plan ahead and stock up for next year

... a fog machine doesn't emit particulates, there are a lot of things that capture vapor that aren't going to adequately deal with particulates, it really isn't a good demonstration for actual smoke, wildfire or otherwise. That said MERV 11 is the absolute minimum for smoke

Matt I've never seen the air so dirty it looks like a monster movie here in the San Joaquin Valley. My brand new Cadillac is covered in ash!

I have been using Levoit and Alen air purifiers and I love them!! All you really need in an air purifier are a prefilter, True HEPA filter, and carbon filter. UV lights and ionizers (which can produce ozone) are really unnecessary.

I have been doing this for years in my workshop.

Thanks for explaining the difference between the Apirilaire (bad spelling) 410 vs 412 vs 413 vs 416. I’ve been using the 410 in my newer HVAC system but just ordered a pair of 413 instead an less cost than from the furnace guys who service it every 6 months. $33.70 for the 413 is better than $54 for the 410 from them.

It seems that installing a higher MERV filter in the whole house system would result in some increase in the negative pressure inside my leaky house, increasing outside infiltration. I'm sealing those leaks but it is a work in process. However the 'standing' or room filters would not affect the house internal negative pressure.

The whole pacific northwest ran out of filters a week ago. Only thing you can get is MERV3. I ended up pulling the filter out of my furnace and blasting it with compressed air before strapping it to a box fan so that I don't have to use my leaky air ducts.

2” filter is the best to use. It has less static pressure across it then the 1”

Hey Matt! Could you doba video on Geothermal heating and how that works with in floor heating. Thanks!

One thing to keep in mind with the typical box fans is that they really are not designed to generate much of a pressure difference. If the pressure drop through the filter is too much then the fan blades stall and almost nothing actually goes through the filter. And no, turning up the fan speed won't help either. Sadly, the thinner filters that can block the smaller particles are often too restrictive for a single fan. Using thicker pleated filters helps a lot. Another thing that can work is making a filter sandwich with two box fans, one on each side of the filter. Just make sure that both fans are working together, one pulling air in one side and the other pushing air out the other side. Doubling up on the fans drops the pressure needed for each fan in half and can make a big difference.

we had some controlled burns where I live and merv 16 works wonders for air quality( merv 16 to 20 are medical grade)

Same issue in New Zealand

Use a 3" or 4" filter on that box fan. A 1" filter clogs too quickly and will burn out the fan motor.

Solid

Great info. Thanks! When you are running a kitchen or bathroom exhaust fan, would it make sense to open a window and insert a Merv-13 filter into the window so it won’t pull in unfiltered air through the cracks in the house? What would be the permanent solution?

it is good to have a house that is a little leaky and has a default passive airflow - use pos pressure hepa to keep it going - if it is all sealed up then you run into problems

I brought a HEPA filter last year, which the wife thought was a waste of money. Around the end of last year into this year we had large fires here in SE Australia, my air monitor only reads up to 999 PM2.5 so all I can say outside it was higher than that, and very high for about a month. Luckily the wife and son where back in Europe but when they came back she brought two more machines, although one is lent out to an old couple one who is on oxygen. We have used them all winter due to our small town is one of the least windest in the world and most people use wood fires for heating. The smoke just falls back down and sits here, often at night the reading is between 80 to 90 PM 2.5 (safe here is taken at below 20, although even this looks to high). Even on our leaky old cheap house the level indoors is dramatically lower with the filters. Best buy we done is these machines, I had sarcoid in my lungs 30 years ago and don't want my son to have to live with damaged lungs.

The trouble with the square box fans is that they don't have a blade shroud, so as you up the filter quality the blades just start recirculating air from in front of the blades. Not saying they don't work at all, but the better you try to make them work, the worse they are. Gotta get a low bypass fan and stick a good filter in front of it. The cheapest Harbor Freight dust collector hooked up to a box with a filter would work a treat, if a little loud.

You should check out Air scrubbers matt

I use Austin Air purifier and 2 box fan filter setups.

I want more whole home central filtration videos

I've used two Blueair units for years. A Blueair Model 400 and Model 600. The important thing to know, is what do the filters cost to replace? Are the filters sold by 3rd party venders - it keeps the cost down. And the noise! How loud is the unit when moving air? Maybe it has a high CFM or room size rating, but sounds like a jet engine. The Blueair 600 has a huge filter surface area and can filter quietly. The pre-filters help the filters last longer and the charcoal does help a lot with odors.

The better the filtration, the better your chances of overheating the motor and sparking a fire. Box fans are not designed to force air through.

Yup!

That's a nice dance floor… er… table you have there.

Please do one on for construction/demolition dust in a house

I have limited space adding another thing just isn't an option. It would be nice if there was an option for adding filters to a mini-split systems or even could replace a dehumidifier with some that dehumidifies and filters. The information on filters is great but would love to know more about odor control options

It is definitely tough times ahead. Big businesses wanting that clean inside air. #sinnisjInsulator

Got one of those big cabinets just included with my recent furnace replacement. Now I wonder if I can upgrade from the merv 11 or 13 it has now to something more beefy without burning out my blower...

do you have a suggestion for how to deal with smoke entering the house through a swamp cooler..?

Hi Matt, Thank you for a grate videos... It’s good to take out the ash particulars how about the toxic gas? Br, Tobbe

Is there any way to fully waterproof windows? Matt from demolition ranch is having that problem and I’d like to know before I replace the windows in my home.🏡

LOVE your videos, but if you'll allow me, I'd like to point out one flaw in your emergency filter demonstration. The fog machine is simply a chemical vapor. The filter media is absorbing it like a sponge. Smoke from a fire contains many things including gases, solids, pollutants and such. PLEASE, I'm not busting your chops, just pointing out something that may have not been considered. Anyway, keep up the videos please. I pull a LOT of information from your channel.

First it was toiletpaper, hand sanitizer and wipes shortages (still no Lysol spray!). Now its a shortage of air filters (HEPA) units! I have Rabbit and Winix models but have a box fan and local home Big Box is out of 20x20... I should put these in my windows ... but what is funny, if you get a HEPA air unit for your bedroom, go and fart near it- it will ramp up! LOL

Hey Matt! I have been following your channel for a while and am loving all of the content! I am wondering if your builder friend up in Seattle has his own youtube channel I can check out. I have been thinking about building my home for a while now. However, a good bit of what you talk about is tailored to where you are in Texas, building zones 2 and 3. I want to find out more about building up here in the Northwest. Thanks!

Unfortunately the “emergency filter” isn’t an option for most in the wild fire areas because all of the hardware stores and box box home stores are completely sold out of air filters of all sizes and types. Living in the pacific NW the air quality index has been in the “hazardous” range from the Oregon/California border to the Canadian border for the past 4-5 days. 3.2 million acres burned in California. 1 million acres burned in Oregon. 1/2 million acres burned in Washington.

is that smoke, or is that water vapor from dry ice quenching? makes a HUGE difference.

There are so many fires in Oregon Matt and Eastern Washington. Please pray for rain.

Matt: Your builder friend in Seattle (you mentioned at 1:11) is not getting smoke from California wildfires, but from the ones in Oregon!

How long will the fan run before the smoke in the room is coming from it's motor? Long-term, the solution for WA is a code change to require their 10% outside air intake to be filtered with an oversized (low pressure drop, high efficiency/effectiveness) high-MERV filter.

Shoot, the smoke in Seattle are from the 7 to 17 large fires in Eastern Washington, blowing over the mountains to the West...

Who makes that return air filter? As others have posted, in the Seattle area box fans and most filters have become hard to find. I feel fortunate that we have multiple room filters we can run (had them for years and Amazon provided the replacement filters when we needed them) and the whole house furnace/AC has a newer filter and an electrostatic filter I cleaned in the Spring. I like that return filter and can see how I might be able to install it on one or maybe both of our returns, depending on where in the flow I could fit it. Who makes that cabinet and filter? Particularly in MERV 16 and above. Thanks, stay safe everyone.

Which haze fluid or what kind of haze machine were you using? Hubs and I both work as techs for live entertainment.

What is your take on the Air Scrubber Plus?

I bought four 20x20 box fans and started experimenting with homemade air filtration using 4 inch 20x20 HEPA furnace filters attached to the back. Even though the fans are a great price, the switch is right in the center axis and took some work to relocate to the top edge. Another downside is the flow was still somewhat restricted. So, I have been considering on building an air filtration cube that would boost my CFM without compromising filtration and yet keep my cost down. I’d like to find a good low cost fan with the switch in a more accessible location or be able to easily rig a remote for the speed control on/off switch. Since space can be a premium, I’m also looking for ways to increase surface area within a smaller volume. Any ideas would be greatly appreciated.

Me 2019: 2020, come at me bro Me 2020: ok stop!!! Uncle! Please stand down!

i can’t find the zoom link to ur live stream happening ryt now about external and internal doors!!!! need to attend

I have been using the box fan and 20x20x1 for years. keeps hair and . . . I sleep with fan on

Those of you/us with severe pollen allergies should look into the Molekule brand of air filters. They are the Mercedes of air filters.

In the UK we have Airfree P150 - is this any good for a medium bedroom of asthma person?

Currently about to start drywall on the Barndo KZfaq built (or I built, thanks to KZfaq). Out in the Hill Country. I've followed a lot of your advice on materials and methods so far and am up against the next big decision. How to seal the shared wall between the garage portion of the building and the apartment. Is two layers of drywall enough? I'd planned Rockwool for that cavity, but could do fiberglass with paper to get a vapor barrier. Or Tyvek or another product? HVAC will consist of a 12k ducted mini and a fresh air system (not as crazy as the new one you built). Exterior walls of the shop are 2"CCF and 3.5" Rockwool and caulked everywhere. So this is the last spot to seal up.

What was the brand name of the metal cabinet retrofit at 7:25?

Time to build a hempcrete house with a steel roof. Bring it fire.