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  • Casey Peelgairdeachas@mastodon.social
    May 30, 2025, 12:10 AM

    I want to brag at how brilliant and crafty my husband @datasaurus is.

    We live in the PNW which in the summer has warm days but cool nights. Indeed many places do not have AC. But I have terrible allergies so just opening up the windows at night to cool the house off makes me miserable.

    So last year he created this filtered air box as part of a kit and rigged it into the living room window so we can bring filtered air in when it's cooler outside.

    But this year he got cleverer.

    1/x

    Picture of a rectangular home built air filter mounted outside a window.
    Inside picture of the same air filter. We can see the six fans what pull air into the house.
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Replies

  • Casey Peelgairdeachas@mastodon.social
    May 30, 2025, 12:18 AM

    After buying some 3Reality plugs and a temperature sensor he now has it wired up to #HomeAssistant. The temperature sensor is outside above the fan. We have another one inside the living room. When the temperature inside is above a set temp, and the temp outside is below it, the fan turns on. When the temp inside is cool enough or outside warms up, it turns off.

    2/x

    Screenshot of a Home Assistant dashboard showing the controls for the window vents. It includes a toggle to manually turn them on or off. The porch and inside temps. An input field to set the desiree inside temp. And the PM 2.5 air quality metric.
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  • Casey Peelgairdeachas@mastodon.social
    May 30, 2025, 12:20 AM

    But the past few years we have to worry about wildfire smoke here in the PNW. So in addition to the temp, he's incorporated the air quality index from the PurpleAir sensor in the neighborhood.

    If the air quality is poor the fan won't come on. If the fan is on and air quality gets too bad, the fan turns off.

    3/x

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  • Casey Peelgairdeachas@mastodon.social
    May 30, 2025, 12:25 AM

    And this is all working brilliantly. The house has big West facing windows, but the porch is on the East. It's 5p here and the air on the porch is cooler than the house so the fan turned on.

    The fan will help cool the house off at night without letting it get too cold. All without turning on the AC or pulling warm air or wildfire smoke inside.

    This is the kind of home automation that feels like you're living in the future, honestly.

    4/4

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  • Casey Peelgairdeachas@mastodon.social
    May 30, 2025, 2:24 PM

    And I was remiss in not posting a link to Clean Air Kits which is where we've gotten all of our Corsi-Rosenthal filters, including the one here in the window and the three luggables we have around the house.

    They are incredibly quiet, easy to put together, use filters you can get at your local hardware store (at least in the US), and very reasonably priced.

    cleanairkits.com/

    5/4

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  • AsbestosAsbestos@pnw.zone
    May 30, 2025, 5:24 AM

    @gairdeachas
    the temp sensor thing really steps up the bar.

    with the same design and some high MERV filters you can create another box inside that will keep the house air smoke free. look up corsi Rosenthal box. they have data that shows they can be more effective than furnace filters.

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  • AsbestosAsbestos@pnw.zone
    May 30, 2025, 10:29 AM

    @gairdeachas
    I'm like a missionary, with those things. trying to get converts. (I also meant HEPA filters, not furnace filters)

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  • tschuuuls9eurosyltbesucher@sueden.social
    May 30, 2025, 11:50 AM

    @gairdeachas if you pull air through an hepa filter, wildfire smoke shouldn't be that much of a problem fyi :)

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  • Casey Peelgairdeachas@mastodon.social
    May 30, 2025, 2:08 PM

    @9eurosyltbesucher I know that @datasaurus did the analysis on the common particulate sizes of wildfire smoke and the filters we're using and decided that it would be best if we didn't try to filter that and just stop the airflow.

    I don't remember the details though and it might have been erring on the side of caution.

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  • M.S. Bellows, Jr.msbellows@c.im
    May 30, 2025, 3:17 PM

    @gairdeachas @9eurosyltbesucher @datasaurus When the wildfire smoke got really bad in Portland in 2020, what made me miserable wasn't the particulates; it was the sulfur dioxide. I bought some specialized 3M filters for an industrial respirator for when it happens again.

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  • Daniel Nidzgorskidatasaurus@mastodon.social
    May 30, 2025, 3:29 PM

    @msbellows @gairdeachas @9eurosyltbesucher Yep, and these particulate-focused furnace filters (or HEPAs) don't really filter out the sulfur dioxide and VOCs and other gases in smoke. So we'll see what PM 2.5 concentration ends up corresponding to too-smoky air that we don't want to pull it in even through these filters. Test and adjust!

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  • MidgePhotomidgephoto@photog.social
    May 31, 2025, 11:25 AM

    @datasaurus @msbellows @gairdeachas @9eurosyltbesucher

    Seems fair.
    Our indoor filter does offer a charcoal layer, optionally. IIRC SO2 would be best handled by passing the air through or over water. Perhaps add a bubble blower or spray to a longer input to the filter.

    Ideally one would pressurise the interior slightly, so fumes didn't seep in through leaks, but that would be very hard here, and in other older houses. PassivHaus standards though...

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  • Daniel Nidzgorskidatasaurus@mastodon.social
    May 30, 2025, 3:19 PM

    @gairdeachas @9eurosyltbesucher These are MERV 13 filters (3M Filtrete 1900), not HEPA. With a single pass through the filter, they'll remove ~95% of the larger pollen particles but ~60% of the smaller smoke particles. The vent shuts off when the outdoor PM 2.5 concentration is twice as high as what we'd want in our house. You're right that HEPA would remove much more smoke (I think >99.9%?), but to pull the same >300 CFM airflow through a HEPA we'd need a *muchmuch* bigger and louder fan.

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  • RichardInSandyrichardinsandy@c.im
    May 30, 2025, 5:22 AM

    @gairdeachas I bet the chap who builds the PurpleAir monitors would be interested to hear about this; they’re built near me & Adrian is a good chap. We have a monitor on our house, a great piece of kit. Your project is ingenious and the sort of thing I wish I could do.

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  • Mozmoz@fosstodon.org
    May 30, 2025, 5:38 AM

    @gairdeachas I have a similar setup but a HEPA filter specifically for the smoke. That works brilliantly for pollen, but also makes the air inside much better on smoke days. Not sure quite how big a HEPA filter you would need for a whole house, but for my passivhaus rated sleepout a "small room" size one lasts months.

    AQI here gets to "wear a mask at all times" levels...

    uradmonitor.com/smoggie-in-syd

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  • bouriquetbouriquet@mastodon.social
    May 30, 2025, 4:42 AM

    @gairdeachas @datasaurus Back in the late 70s, we lived in a small craftsman bungalow in West Seattle. One of the upper kitchen cabinets was on an outside wall to the back porch and had a sliding board that let cool outside air into the cabinet through several holes covered by a screen. Kinda like cool storage for potatoes and other root crops. Simple and effective.

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  • Jon Clausenj_a_clausen@mastodon.social
    May 30, 2025, 6:04 AM

    @gairdeachas @datasaurus I've done something similar to control the fan on our bathroom:

    Humidity sensor inside bathroom, humidity sensor outside the bathroom, both connected to an arduino, which controls a relay that controls the fan.

    When the shower is used, inside humidity rises, crosses threshold, fans turns on. When humidity is brought down, fan stops.

    1/x

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  • Jon Clausenj_a_clausen@mastodon.social
    May 30, 2025, 6:05 AM

    Because of "residual" humidity, I had to add a "hysteresis" mechanism.
    Start condition is "outside + 20%".
    Stop conditions are: "outside + 10%, if fan is running" OR "inside <= outside".

    Without this, the fan would enter a long period of switching on/off as the humidity fluctuated in the air surrounding the sensor until humidity inside and outside were equal.

    Very simple and naïve, but it works surprisingly well

    2/2

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  • Casey Peelgairdeachas@mastodon.social
    May 30, 2025, 2:15 PM

    @j_a_clausen Very nice and a great use of home automation!

    @datasaurus built hysteresis into the start criteria for the fan start-up as well for the same reason. IIRC, the temperature spread between outdoors and indoors needs to be at least 2 degrees for 5 minutes. Ditto air quality metric. The stop criteria are currently immediate though, erring on the side of not inadvertently warming up the house.

    It's still early and we may need to adjust the thresholds but it's working well so far!

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  • Charlie Parkcharliepark@xoxo.zone
    May 30, 2025, 4:48 PM

    @gairdeachas @datasaurus So cool! Thank you for sharing! You probably know this, but in HVAC-world, the kind-of-goofy term for that device is an "economizer", in case you're looking for scaled-up prior art. Regardless, can see why you're proud of him!

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  • NilaJonesNilaJones@zeroes.ca
    May 31, 2025, 4:10 AM

    @gairdeachas @datasaurus

    I have something similar but less snazzy!

    I just used an off-the-shelf air purifier and a bunch of weather stripping. It's been in place for 5 years, in my window

    I find the HEPA filters work pretty well for bringing in fresh air even when it is very smokey out! I do run a freestanding air purifier inside the house in addition, to catch any bits of smoke that make it through the first filter

    And I change the filter after the air clears up. Because I am cheap, I save the smokey filter in case I want to use it again on a very smokey day

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  • Daniel Nidzgorskidatasaurus@mastodon.social
    May 31, 2025, 4:30 AM

    @NilaJones @gairdeachas That sounds pretty cool! Do you have photos by chance? I couldn't figure out how to rig a typical HEPA purifier into the window, which is part of the reason why I went for this box.

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  • NilaJonesNilaJones@zeroes.ca
    May 31, 2025, 4:44 AM

    @datasaurus

    I could probably take a photo tomorrow if you really want one. I'm worn out for today!

    I did mine before the kits were on the market. If I were to do it again I might use a kit, like you did

    I think the kit ones are better for this purpose, because of the squared off corners. Commercial purifiers all seem to have rounded plastic housing, which requires more weather stripping and fiddling

    After a while I got tired of messing with weather stripping, and just covered the whole perimeter with blue masking tape. The weather stripping is behind that. So it looks kind of funky

    My install is different because I have a double hung window instead of a slider. After scrolling through about 10,000 choices of commercial purifiers, I found one that was exactly the width of my window opening, and, more difficult to find, had the intake at 180° from the outflow. (Most commercial units are 90°.) Also important was to make sure the buttons are accessible, to turn it off and on when installed!

    My install is on the upwind side of the building, so I used a piece of 10-inch wide flashing to make a little slanted roof over the top of the purifier, to keep it dry in the rain

    I can change the filter easily from the outside, without having to take the unit out of the window. The back cover is removable without tools. This is a very good feature, and doing again, I would look for it. Maybe I could find or modify a kit, to allow replacing the filters without taking the fan portion out of the window

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  • Catcatmisgivings@stranger.social
    May 31, 2025, 11:25 AM

    @gairdeachas @datasaurus high 5 from someone with allergies who only breathes filtered air. Always wondered how I'd manage in the PNW and now I have some ideas!

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