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I'm amazed by how complex indoor air quality is. Heating, cooling, filtering, cycling outdoor air... none of it is as straightforward as you'd hope. I noticed a

I'm amazed by how complex indoor air quality is. Heating, cooling, filtering, cycling outdoor air... none of it is as straightforward as you'd hope. I noticed a substantial improvement in my health when I started putting HEPA air filters all over my house, and another jump when I moved away from a major road. Now COVID-19's airborne spread has bumped this issue from annoyance to life and death. It seems like this is an area where IoT should really deliver the goods. I should be able to cheaply add networked sensors, fans, filters, and vents to my home to automatically monitor air quality and temperature, then take appropriate action. Sadly, we're basically stuck with smart thermostats that spy on you and deliver little benefit over a local solution. I had a lot of hope for IoT air conditioning vents, but those products never seemed to materialize. Indoor air quality monitors are expensive and inaccurate. Nobody is offering me a real-time fluid dynamics model of the heat and pollutant situation in my home, let alone responding to it appropriately. Amazing how hard it is to create reliable, computable models of the world...

sjg007 6y ago
New homes have ERVs or HRVs and some have ventilating dehumidifiers. You could put an AQI sensor on it to run them as needed but generally they are either timed per hour and on a humidistat. New homes also have to have gas appliances (except for the stove) with their own air intake and powered exhaust. All gas stoves should be below a hood with a ducted outside vent, the more powerful the better.
- pbronez 6y ago
  I'm not familiar with those acronyms. Googling suggests ERV = Energy Recovery Ventilator [0] and HRV = Heat Recovery Ventilator [1]. Wikipedia says these are mostly about energy efficiency but also have air quality benefits. It's not clear to me how this helps with indoor air quality - maybe better humidity and temperature regulation? They also seem to require a centralized air conditioning/heating system. That would give you a nice central place to put an air quality monitor. The big challenge though is that often these central systems don't process all air in the building evenly. Multi-zone systems help. 1000% agree on the venting. It occurs to me that I have some gas heaters that I should double-check the venting on... [0] https://en.wikipedia.org/wiki/Energy_recovery_ventilation https://en.wikipedia.org/wiki/Energy_recovery_ventilation [1] https://en.wikipedia.org/wiki/Heat_recovery_ventilation https://en.wikipedia.org/wiki/Heat_recovery_ventilation
  - Retric 6y ago
    Having a heat exchanger let’s you exchange large quantities of outside air with indoor air at minimal costs. Trading 70f indoor air with -30f outside air is bad, moving heat between them means could be venting air closer to -10f and only need to heat the new air from 50f to 70f You still want a quality filter and humidity is an issue in some areas, but overall they can make a huge difference.
    - telchar 6y ago
      Wouldn't a heat exchanger top out at equalizing the inward and outward bound air at 20F in this case?
      - deleted 6y ago
        [deleted]
      - gns24 6y ago
        No. Imagine that your heat exchanger is simply two touching pipes running parallel to each other, with flows in opposite directions. Incoming air will gradually warm up as it comes inwards, eventually being warmed by the air which has just left the room. You can get a much better result than just averaging the temperatures.
      - kens 6y ago
        The idea is "countercurrent exchange": the incoming air and outgoing air travel in opposite directions through the heat exchanger. The result is that most of the heat gets transferred. At the end of the exchanger, the warmed incoming air is in contact with 70° outgoing air, so it will be at almost 70°. Similarly, the outgoing air will be at almost -10° as it exits. It will probably make more sense if you look at the diagram: https://en.wikipedia.org/wiki/Countercurrent_exchange https://en.wikipedia.org/wiki/Countercurrent_exchange
        robocat 6y ago
        Fun fact: "An example of countercurrent heat exchange occurs in the feet of penguins, in which heat from blood in the arteries supplying the feet is transferred to blood returning to the body's core in veins that lie close to these arteries."
- macNchz 6y ago
  > All gas stoves should be below a hood with a ducted outside vent, the more powerful the better. To my understanding, installing a very powerful stove hood in a tightly sealed house without proper consideration for a make-up air intake can cause problems (i.e. backdrafts in the exhausts for gas fired water heaters), especially in concert with other things venting outside like a clothes dryer. It's very possible to have it done right, but a pretty bad situation if done wrong.
  - yetihehe 6y ago
    Newer gas fired water heaters (mine is 10yr old) with closed chamber have special chimneys where your exhaust and intake go through double walled pipe with counterflow, which helps with energy recovery (exhaust goes through inside pipe, fresh air goes in outside pipe and gets heated by exhaust gases). That also means you don't need to have proper intake where the heater is (but there still needs to be some ventilation).
  - sjg007 6y ago
    Yep, it is subject to building code requirements. This is why installing ducted vent hoods usually requires a permit etc...
- exhilaration 6y ago
  New homes have ERVs or HRVs What country are you in? I'm in the US and my nice home, built in 2015, doesn't have either one.
  - zip1234 6y ago
    As far as I know they only put them in the super expensive houses that are made extremely tight. If they use spray foam insulation then there is very little air circulation so that they need to add an ERV just to get enough air to breath.
  - sjg007 6y ago
    Check your code requirements. I am in the USA and they are required, but I am in the north where we have very cold winters and humid summers. You should consider putting one in if you don't have one.
    - exhilaration 6y ago
      I'm in Pennsylvania! But maybe that's not north enough for them to be required.
- com2kid 6y ago
  > All gas stoves should be below a hood with a ducted outside vent, the more powerful the better. The best part is how many "down draft" vents are put into place, even new luxury construction. They look nice, but don't do much...
- dota_fanatic 6y ago
  Are there any quality brands that have a vent that can be directed outdoors? We're renovating our kitchen in the next year and are planning on doing this, but haven't had any luck finding a natural gas stove which is made to vent outdoors. I don't have counter evidence on hand but assuming the oven is vented outdoors, my understanding is that a hood should be relatively low-powered, not high, in order to then capture emissions from the stove top. It should be a function of size, height from the stove top, noise constraints, etc.
  - sjg007 6y ago
    You can calculate the minimum CFM required to vent your stove top and oven based on BTUs and room size. Your CFM calculation will also inform duct size and make up air requirements. Lots of sites do this but here's one. https://www.prolinerangehoods.com/blog/cfm-need-range-hood/ https://www.prolinerangehoods.com/blog/cfm-need-range-hood/ You can vent both the gas oven and the stove separately. You have to buy high end appliances for that. I've seen them but can't remember.. maybe a Viking stove or something prosumer-commercial. Make up air can be a cracked window or a separate intake duct that opens up when the vent is turned on. Your local building code will have specific requirements. You can duct a hood out of an external wall or even better out of the roof. If you go with a roof vent you can install the extractor fans in the duct in the attic which helps reduce noise if that's a concern. What you can do will depend on your specific kitchen. I have found that the stove top is worse than the oven for emissions. The reason is that my exhaust hood is under-powered and it's a microwave/exhaust combination that doesn't extend over the entire cooking surface. So I would advise a hood larger than the stove top itself, install a larger duct and I would overestimate the CFMs required. If you get a multi-speed range hood then you can adjust it as necessary. I actually think electric ovens are better combined with a gas stove top. Electric ovens though do have a tendency to fail at inopportune times (e.g. the holidays!)
- lostapathy 6y ago
  What part of the country are you in, and what price range, where new homes have ERV or HRV installed? I'm in Kansas City, and even into the $650k range, houses only VERY rarely are built with them.
  - bluGill 6y ago
    20 years ago the building code in MN required them, or some other form of ventilation. (leaving the bathroom fan on constantly would probably meet the letter of the law, but no contractor I know of was willing to try to get past the inspectors). Different states have different codes, so and I am not up to date on what the latest is anywhere anymore.
    - lostapathy 6y ago
      A lot of places building codes "require them" at a high level, and then more local building codes strike provisions like this, or provide "alternate paths" to legality. It's disgusting. Like around here, the building code in one city requires a certain blower door score to pass. But doesn't require blower door testing if you say you followed certain "sufficient" practices. There's no way most of these houses would achieve a sufficient blower door test score, but they all "comply with code".
alisonkisk 6y ago
"Internet" is not needed for any of those feature ideas.
- whichquestion 6y ago
  Maybe locally networked is what they meant
  - darksaints 6y ago
    I would hope. There's some usefulness for alarm-level conditions to communicate with the outside world...but it is really disappointing how many devices feel the need to phone home about nothing in particular.
  - pbronez 6y ago
    I think the the key is to have multiple sensing and acting devices working together to create and act on a high-quality model of the interior environment. My preference would be to self-host that model and the associated controls. I suspect this would require some meaningful compute capability in-house.
- deleted 6y ago
  [deleted]
- pbronez 6y ago
  True, I'd be happy to self-host the meat of a system like this. However, I suspect that the problem would benefit from cloud-scale compute. It's a fluid dynamics problem, which is just a lot of numbers to crunch. This might require more horsepower than a little ARM device can reasonably push out.
samstave 6y ago
PLANTS LOTS AND LOTS OF PLANTS One of the best filters out there is a spikey plant that you wouldnt think of as "pretty" but it is super helpful https://leafyplace.com/air-filtering-house-plants/ https://leafyplace.com/air-filtering-house-plants/ While is #10 on this list, its still SUPER good at filtering... I Personally like LOTS of Pothos and Spider plants....
- csnover 6y ago
  You’re technically right about the “lots and lots” part, though I suspect you don’t understand how much “lots and lots” actually is: > To reduce VOCs enough to impact air quality would require around 10 plants per square foot. In a small 500-square foot apartment, that’s 5,000 plants.[0] Potted plants do not improve indoor air quality: a review and analysis of reported VOC removal efficiencies[1] [0] https://www.nationalgeographic.com/science/2019/11/houseplants-dont-purify-indoor-air/ https://www.nationalgeographic.com/science/2019/11/houseplan... [1] https://www.nature.com/articles/s41370-019-0175-9 https://www.nature.com/articles/s41370-019-0175-9
  - samstave 6y ago
    huh. thanks for that info. I just like plants in general... vertical walls in specific though I have yet to build my own (built the ones with architects in Salesforce office around the country) but now I am craving more plants!! (and moss) ((and fungi)) (((planning on composting all these leaves with seeded fungi spores, just need to find the spores)))
- jacquesm 6y ago
  This is bad advice. Plants are good for air quality in the sense that they filter out some dust and exchange CO2 for O2, but they also add to the contaminants, are a frequent source of fungi and other pests, require a lot of maintenance to stay healthy and are expensive in the quantities required to have a measurable impact on air quality. They are pretty though and if you have the time and the room for them they definitely are worth having but $ for $ if your goal is clean air technology is far more efficient.
beerandt 6y ago
Call a pro. AC systems are not DIY. The things you're looking for exist (and are often mandatory) in the commercial/ non-residential market, but they are not IoT, and they aren't cheap. For instance, most commercial spaces have a MAX value on percentage of recycled air; a minimum amount of air fed into the return must be fresh air drawn from outside. >should be able to cheaply add networked sensors, fans, filters, and vents Sensors can be ok... But your homes's AC design, even if based on simple building code lookups, is based on some fairy complex engineering which rely on certain assumptions. If those assumptions aren't met, the design usually must be approved by a licensed engineer. This is why you don't see more independently controlled vents on the market. No professional is going to install products that don't meet code, unless an engineer has stamped the plans. (Which includes operational logic.) Ignoring regulations, you shouldn't just add controlled vents to a system (or manually close existing vents) without compensating for that elsewhere. You likely need a variable speed blower, controlled/compensated return air flow, and system logic to control it all. Will the house blow up if you install them yourself? Probably not. But it could result in a system operating much less efficiently, increase the number of system cycles (reducing system lifetime), cause duct ruptures/leaks due to increased back pressure, and most likely, cause condensation in places other than the condenser, possibly causing mold to grow and/or rot. Which leaves 2 options: installing a commercial system with the integrated vent control you're looking for, or adding sensors for input for when the system should run, without modification. Biggest simple change you can make for immediate impact? Change your filters every month, even if it means using 12 $3 fiberglass filters instead of 1 $36 hepa filter. For instance, I run a list of room temps through a simple max function to ensure my AC and/or blower runs until the hottest room falls below the set temperature. If this results in wildly unbalanced temps throughout the house, you have a bigger issue, and likely need your system resized/adjusted by a professional. Related, and because most people don't realize it, your AC is an engine. You want it properly sized and to run constant, when needed. Think of your car: is it more efficient to make a trip by many intermittent 100mph sprints, or driving 55mph without stopping. Multi stage compressors now act like car transmissions to dynamically "size" the system as needed, but run constantly with minimal stopping.
- jacquesm 6y ago
  This is all spot on. The engineering that goes into HVAC systems is under appreciated. When messed up the system that is supposed to give you fresh air can easily become a source of pathogens. You also want filters on ingress and egress (to ensure critters don't have a path into your house), and you want to have a nice fat overdimensioned heat exchanger between the two airstreams to ensure that you're not heating the world instead of your house. +1 on the rapid change of filters, much better to change a filter frequently even if it is a bit lower performance than to let one sit for too long, but keep an eye on your electricity cost, that is the factor that should decide the quality filter that you purchase and frequently you replace it. Ground rule: the better the filter, the more it will absorb, the better the chances that something you really don't want lodges there and starts spreading if the filter gets overloaded. Fiberglass filters are a good compromise between energy efficiency and cost, they have excellent working surface compared to their physical size and tend to have a relatively long working life before they 'join the other side' and become a source of contaminants rather than a filter of contaminants.
Chris2048 6y ago
> IoT should really deliver the goods IOT is a signal for "large disposable income", so HEPA/health anything associated with IoT will bump up the price tag considerably. Why would anyone deliver anything good when people already willingly paying for crap?
AndyMcConachie 6y ago
I went down the rabbit hole of air quality testing devices a couple years ago. The bottom line, AFAICT, it is not easy to accurately test air quality cheaply. Whenever I would find a device that claimed to test air quality I would find reviews by people who were testing that device that stated either; It came miscalibrated from the factory. OR After a short period it would no longer be calibrated. Turns out keeping an air quality testing device calibrated properly is really really hard, and definitely not cheap. So maybe the computing side of this is not really all the difficult, but the physical measurement side of this is absolutely not easy. Eventually I gave up trying to find a device for my home because I realized I would have to really dig into the science hard, and I would have to spend more money than I was willing. And I was unwilling to do either.
- jschwartzi 6y ago
  I've not worked specifically with contaminant sensors, but I know oxygen sensors require very specific and very consistent flow rates across the element. The type I've worked with used a ceramic element which absorbs oxygen and changes resistance as a result. So increased or decreased oxygen results in increased or decreased resistance. Using a sensor like this to measure percent of oxygen in a gas requires you to eliminate a lot of confounding effects like pressure waves, flow changes, etc.. Basically you can cause the sensor to absorb more oxygen than is present in the gas by temporarily increasing flow. So if you're building an air quality sensor you have to pay very close attention to how the air moves through the sensor. That requires not just a calibration but also characterization of the flow through the system under environmental conditions. One other effect I could see is a contaminant sensor becoming fouled. Oxygen sensors can become fouled and report inaccurate values, which is why it's very important to control the inputs. This is one of the reasons an antifreeze leak in an engine block can cause your engine performance to go to crap. The oxygen sensor is part of how a stoichiometric ratio of fuel and air is maintained, by monitoring the combustion products for excess oxygen. So when it gets fouled either the ceramic element is damaged or the sensor stops receiving consistent flow and the resistance relationship ceases to be valid. In short I don't see how you could build a useful long-lasting sensor by just buying parts off Amazon or Digikey and throwing them together. You would have to treat it like a scientific instrument, meaning that you have to validate your assumptions about how the sensor performs and I doubt that most of the products on Amazon do that.
Diederich 6y ago
Hey there...I appreciate your comment. > I started putting HEPA air filters all over my house Can you very briefly say how you accomplished this? Was it with modified box fans? Thank you!
- jcims 6y ago
  Just a plug for Coway Airmega. I bought the 400, which is expensive, but it was for someone with health issues. I absolutely love it. Super quiet on low speeds and has been about as low maintenance as one could expect. Filters seem to be of exceptionally high quality and overall build is great.
- nawgz 6y ago
  I did this - I just bought things off Amazon. Bissell air220 chunks through most of my apartment, and a couple small ones sit in the "leaf node" rooms
- Alex3917 6y ago
  Just buy one and plug it in: https://www.nytimes.com/wirecutter/reviews/best-air-purifier/ https://www.nytimes.com/wirecutter/reviews/best-air-purifier...
- pbronez 6y ago
  I purchased several stand-alone Air Purifier appliances for something like $100-200 each [0]. They have two kinds of filters that work in tandem, you replace one every month and the other every three months. It gets expensive to replace all the filters when you have several of them, but they pull a ton of junk out of the air. [0] https://www.winixamerica.com/product/5300-2/ https://www.winixamerica.com/product/5300-2/
- Raphmedia 6y ago
  Several people have recommend you air purifiers. I would add one thing, look at the price of replacement filters. Air filters are similar to printers in a way. You become tied to a company and have to buy replacement pieces every year or so. Some have bad track record (quick device depreciation because of out of stock filters, etc.)
Nacdor 6y ago
> I noticed a substantial improvement in my health when I started putting HEPA air filters all over my house, and another jump when I moved away from a major road. Same for me when I moved out of a stuffy old high-rise in Philadelphia. I had frequent coughs and wheezing, shortness of breath, and just lots of general discomfort with breathing. Every time I washed my car there was a thick black layer of soot covering it within a couple days, so I'm sure that was doing great things for my lungs. Also got a couple serious colds every year when I lived there. That was as a 20-something who never smoked, didn't have asthma and wasn't overweight. Living in the suburbs now and haven't had an issue since moving.
- kaitai 6y ago
  Air quality and health are quite significant in predicting COVID mortality on a neighborhood by neighborhood basis, too. Environmental air quality -- socioeconomic status -- health outcomes (and more) are tied in a very complex network with a lot of reinforcing cycles. I don't know what the distribution of stove type by income level is, but I do have the impression that richer Americans are more likely to have fancy induction ranges, and poorer Americans are more likely to use gas. Annoying as I certainly find gas more pleasant to cook with.
  - supertrope 6y ago
    When I think of a cheap apartment I imagine a stove with electric resistive coils.
    - phil21 6y ago
      Indeed. The only rentals with gas stoves are either the high-end market, or legacy housing stock probably 50+ years old. Any lower/middle class oriented apartments I've seen built in the past 30 years in my area at least have all been electric. Also spent a lot of my 20's in cheap apartments, and never had anything more than an electric coil stove.
      - jdhn 6y ago
0xbadcafebee 6y ago
> It seems like this is an area where IoT should really deliver the goods. I should be able to cheaply add networked sensors I think you're going the wrong way. These problems were caused by trying to artificially exert control over a complex environment. Similar to trying to "manage" a natural environment, each effort results in 2 more side-effects which each then need their own "management". On the other hand, some modern "management" techniques are to simply re-introduce nature to an environment and letting it self-manage. This ends up with better ecological health as well as less cost and complexity. But we have to let go of whatever weird human-specific desire caused us to mismanage it the first time. Why do we need carbon monoxide monitors? Because carbon monoxide builds up, because gas-powered devices and heat exchangers live inside the sealed home. Put them outside the home and the problem is solved, no technological solutions necessary. A properly designed home can also avoid things like vapor barriers, reduce dependence on air conditioning and heating, avoid mold and mildew, and require less maintenance. But if we insist on working within existing home designs, there's a constant requirement for new fixes for the new problems we introduce.
- briefcomment 6y ago
  This is a great idea. Do you know of any further reading on fundamentally redesigning housing in practical ways?
  - 0xbadcafebee 6y ago
    Sadly I don't have reading suggestions. I've kind of gathered details over time. My own "redesign" is just to look at how homes used to work. Wattle and daub, hogan, pueblo, timber frame, log cabin, long house, clochán, crannog, igloo, walpini, adobe, brick. They each have pros and cons, but they work best for where they were built and the needs of the people that lived there. They adapted solutions for heating/cooling, pest control, weather resistance, cooking, storage, etc that fit their purpose. As far as I know, none of these homes ever had to deal with annoyances like mold or carbon monoxide. But then again the downsides could be severe in densely-populated urban areas; entire cities could be razed overnight by fire and strong winds! Before modern homes were redesigned to take advantage of supply chain efficiencies, timber frame and stone foundation were common in the US. Before air conditioning, homes were designed for where they sat to take the seasons into account. A central corridor of air could be funneled by opening doors or windows on either side of the house, rapidly cooling or heating it, and windows and shutters could lock in whatever the temperature was - but this would be a bad idea on a humid day! A stone foundation acted as a mini thermal battery, and some building materials were incredibly good insulators. Also common were fireplaces and living quarters in the center of the home; shut all the doors to keep your room toasty warm, or open them up to warm the house for company. There was no vapor barrier, no sheeting; just nail some shingles to the frame and stuff whatever you can into the walls for insulation, or build walls out of a composite like mud and stick. In wet, hot areas, you had lots of porches and big awnings so you could stay outside with a fan in the shade. There's many other old-school techniques we could be using, but then homes become more expensive as no contractor knows how to build them, or we've literally done away with all the natural resources and now they have to be acquired at great expense. Not to mention of course, zoning might have made it all illegal anyway. In many ways we've engineered ourselves into a corner.
Aardwolf 6y ago
> It seems like this is an area where IoT should really deliver the goods. A combination of sensors and actuators to fix the air problem, yes. But where does the internet come into play here? Seems like something 100% local to me. Except if you want to view the data remotely, but that's a side feature, not a main requirement for this to work.
- 0xffff2 6y ago
  I think it comes into play because LANoT doesn't roll off the tongue the way IoT does.
  - deleted 6y ago
    [deleted]
turtlebits 6y ago
I have an Awair unit and it's fairly inexpensive. I can't vouch for the accuracy, but I saw DHH post about it and compare it other consumer sensors and more "professional" sensors and he recommended it. One of the main problems is that homes are not built for indoor air quality. Furnaces in crawl spaces or garages, lack of air sealing. You can't just add sensors and fans to fix the problem. Plus, adding a fan/vent to a home isn't ever going to be cheap. You're talking about cutting the interior and exterior of your house, running ducting and wiring up electrical.
- Raphmedia 6y ago
  > I have an Awair unit and it's fairly inexpensive. I have an anecdote about the Awair. The air at one of my previous workplace was making me sick, so I asked the management to look at the air quality. They hired a professional who saw nothing - because they asked for the AC to be turned off during the monitoring. I got an Awair and managed to track when the air quality dropped. It was whenever the AC came on. They then called another professional who finally caught it -- turns out the building's ventilation ducts had not been cleaned in 5 years AND there was water damage. Without a customer grade air quality tracker, I would have simply believed the first professional. I would have had to either suffer being sick daily at work or having to quit for air quality reason. Now I carry mine around to my friends and family's house and let them borrow it for a while. It always come up with explanations about issues people had been quietly enduring forever.
  - s5300 6y ago
    Hi - can you tell me the model you bought?
    - Raphmedia 6y ago
      I have the Awair 2nd Edition. It is similar to the Awair Element. However, as I don't have a smart home I sometime wish I had an Awair Glow C instead (disclaimer, it does not have as many sensors). It's a smart plug, so it can turn off the device you plug into it... I would plug my air purifier or maybe my air humidifier to it. If you want to use one suche device on the go, at friends places, etc., I'd recommend the Atmotube Plus or Atmotube Pro by Atmotube (depending on your needs). My purchase was a few years ago now. I've heard that the market is bigger now, so you may want to shop around. I also have the big Dyson purifier at home which comes with built-in sensors.
deleted 6y ago
[deleted]

sjg007 6y ago

New homes have ERVs or HRVs and some have ventilating dehumidifiers. You could put an AQI sensor on it to run them as needed but generally they are either timed per hour and on a humidistat. New homes also have to have gas appliances (except for the stove) with their own air intake and powered exhaust. All gas stoves should be below a hood with a ducted outside vent, the more powerful the better.

pbronez 6y ago
I'm not familiar with those acronyms. Googling suggests ERV = Energy Recovery Ventilator [0] and HRV = Heat Recovery Ventilator [1]. Wikipedia says these are mostly about energy efficiency but also have air quality benefits. It's not clear to me how this helps with indoor air quality - maybe better humidity and temperature regulation? They also seem to require a centralized air conditioning/heating system. That would give you a nice central place to put an air quality monitor. The big challenge though is that often these central systems don't process all air in the building evenly. Multi-zone systems help. 1000% agree on the venting. It occurs to me that I have some gas heaters that I should double-check the venting on... [0] https://en.wikipedia.org/wiki/Energy_recovery_ventilation https://en.wikipedia.org/wiki/Energy_recovery_ventilation [1] https://en.wikipedia.org/wiki/Heat_recovery_ventilation https://en.wikipedia.org/wiki/Heat_recovery_ventilation
- Retric 6y ago
  Having a heat exchanger let’s you exchange large quantities of outside air with indoor air at minimal costs. Trading 70f indoor air with -30f outside air is bad, moving heat between them means could be venting air closer to -10f and only need to heat the new air from 50f to 70f You still want a quality filter and humidity is an issue in some areas, but overall they can make a huge difference.
  - telchar 6y ago
    Wouldn't a heat exchanger top out at equalizing the inward and outward bound air at 20F in this case?
    - deleted 6y ago
      [deleted]
    - gns24 6y ago
      No. Imagine that your heat exchanger is simply two touching pipes running parallel to each other, with flows in opposite directions. Incoming air will gradually warm up as it comes inwards, eventually being warmed by the air which has just left the room. You can get a much better result than just averaging the temperatures.
    - kens 6y ago
      The idea is "countercurrent exchange": the incoming air and outgoing air travel in opposite directions through the heat exchanger. The result is that most of the heat gets transferred. At the end of the exchanger, the warmed incoming air is in contact with 70° outgoing air, so it will be at almost 70°. Similarly, the outgoing air will be at almost -10° as it exits. It will probably make more sense if you look at the diagram: https://en.wikipedia.org/wiki/Countercurrent_exchange https://en.wikipedia.org/wiki/Countercurrent_exchange
      - robocat 6y ago
        Fun fact: "An example of countercurrent heat exchange occurs in the feet of penguins, in which heat from blood in the arteries supplying the feet is transferred to blood returning to the body's core in veins that lie close to these arteries."
macNchz 6y ago
> All gas stoves should be below a hood with a ducted outside vent, the more powerful the better. To my understanding, installing a very powerful stove hood in a tightly sealed house without proper consideration for a make-up air intake can cause problems (i.e. backdrafts in the exhausts for gas fired water heaters), especially in concert with other things venting outside like a clothes dryer. It's very possible to have it done right, but a pretty bad situation if done wrong.
- yetihehe 6y ago
  Newer gas fired water heaters (mine is 10yr old) with closed chamber have special chimneys where your exhaust and intake go through double walled pipe with counterflow, which helps with energy recovery (exhaust goes through inside pipe, fresh air goes in outside pipe and gets heated by exhaust gases). That also means you don't need to have proper intake where the heater is (but there still needs to be some ventilation).
- sjg007 6y ago
  Yep, it is subject to building code requirements. This is why installing ducted vent hoods usually requires a permit etc...
exhilaration 6y ago
New homes have ERVs or HRVs What country are you in? I'm in the US and my nice home, built in 2015, doesn't have either one.
- zip1234 6y ago
  As far as I know they only put them in the super expensive houses that are made extremely tight. If they use spray foam insulation then there is very little air circulation so that they need to add an ERV just to get enough air to breath.
- sjg007 6y ago
  Check your code requirements. I am in the USA and they are required, but I am in the north where we have very cold winters and humid summers. You should consider putting one in if you don't have one.
  - exhilaration 6y ago
    I'm in Pennsylvania! But maybe that's not north enough for them to be required.
com2kid 6y ago
> All gas stoves should be below a hood with a ducted outside vent, the more powerful the better. The best part is how many "down draft" vents are put into place, even new luxury construction. They look nice, but don't do much...
dota_fanatic 6y ago
Are there any quality brands that have a vent that can be directed outdoors? We're renovating our kitchen in the next year and are planning on doing this, but haven't had any luck finding a natural gas stove which is made to vent outdoors. I don't have counter evidence on hand but assuming the oven is vented outdoors, my understanding is that a hood should be relatively low-powered, not high, in order to then capture emissions from the stove top. It should be a function of size, height from the stove top, noise constraints, etc.
- sjg007 6y ago
  You can calculate the minimum CFM required to vent your stove top and oven based on BTUs and room size. Your CFM calculation will also inform duct size and make up air requirements. Lots of sites do this but here's one. https://www.prolinerangehoods.com/blog/cfm-need-range-hood/ https://www.prolinerangehoods.com/blog/cfm-need-range-hood/ You can vent both the gas oven and the stove separately. You have to buy high end appliances for that. I've seen them but can't remember.. maybe a Viking stove or something prosumer-commercial. Make up air can be a cracked window or a separate intake duct that opens up when the vent is turned on. Your local building code will have specific requirements. You can duct a hood out of an external wall or even better out of the roof. If you go with a roof vent you can install the extractor fans in the duct in the attic which helps reduce noise if that's a concern. What you can do will depend on your specific kitchen. I have found that the stove top is worse than the oven for emissions. The reason is that my exhaust hood is under-powered and it's a microwave/exhaust combination that doesn't extend over the entire cooking surface. So I would advise a hood larger than the stove top itself, install a larger duct and I would overestimate the CFMs required. If you get a multi-speed range hood then you can adjust it as necessary. I actually think electric ovens are better combined with a gas stove top. Electric ovens though do have a tendency to fail at inopportune times (e.g. the holidays!)
lostapathy 6y ago
What part of the country are you in, and what price range, where new homes have ERV or HRV installed? I'm in Kansas City, and even into the $650k range, houses only VERY rarely are built with them.
- bluGill 6y ago
  20 years ago the building code in MN required them, or some other form of ventilation. (leaving the bathroom fan on constantly would probably meet the letter of the law, but no contractor I know of was willing to try to get past the inspectors). Different states have different codes, so and I am not up to date on what the latest is anywhere anymore.
  - lostapathy 6y ago
    A lot of places building codes "require them" at a high level, and then more local building codes strike provisions like this, or provide "alternate paths" to legality. It's disgusting. Like around here, the building code in one city requires a certain blower door score to pass. But doesn't require blower door testing if you say you followed certain "sufficient" practices. There's no way most of these houses would achieve a sufficient blower door test score, but they all "comply with code".

alisonkisk 6y ago

"Internet" is not needed for any of those feature ideas.

whichquestion 6y ago
Maybe locally networked is what they meant
- darksaints 6y ago
  I would hope. There's some usefulness for alarm-level conditions to communicate with the outside world...but it is really disappointing how many devices feel the need to phone home about nothing in particular.
- pbronez 6y ago
  I think the the key is to have multiple sensing and acting devices working together to create and act on a high-quality model of the interior environment. My preference would be to self-host that model and the associated controls. I suspect this would require some meaningful compute capability in-house.
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pbronez 6y ago
True, I'd be happy to self-host the meat of a system like this. However, I suspect that the problem would benefit from cloud-scale compute. It's a fluid dynamics problem, which is just a lot of numbers to crunch. This might require more horsepower than a little ARM device can reasonably push out.

samstave 6y ago

PLANTS LOTS AND LOTS OF PLANTS One of the best filters out there is a spikey plant that you wouldnt think of as "pretty" but it is super helpful https://leafyplace.com/air-filtering-house-plants/ https://leafyplace.com/air-filtering-house-plants/ While is #10 on this list, its still SUPER good at filtering... I Personally like LOTS of Pothos and Spider plants....

csnover 6y ago
You’re technically right about the “lots and lots” part, though I suspect you don’t understand how much “lots and lots” actually is: > To reduce VOCs enough to impact air quality would require around 10 plants per square foot. In a small 500-square foot apartment, that’s 5,000 plants.[0] Potted plants do not improve indoor air quality: a review and analysis of reported VOC removal efficiencies[1] [0] https://www.nationalgeographic.com/science/2019/11/houseplants-dont-purify-indoor-air/ https://www.nationalgeographic.com/science/2019/11/houseplan... [1] https://www.nature.com/articles/s41370-019-0175-9 https://www.nature.com/articles/s41370-019-0175-9
- samstave 6y ago
  huh. thanks for that info. I just like plants in general... vertical walls in specific though I have yet to build my own (built the ones with architects in Salesforce office around the country) but now I am craving more plants!! (and moss) ((and fungi)) (((planning on composting all these leaves with seeded fungi spores, just need to find the spores)))
jacquesm 6y ago
This is bad advice. Plants are good for air quality in the sense that they filter out some dust and exchange CO2 for O2, but they also add to the contaminants, are a frequent source of fungi and other pests, require a lot of maintenance to stay healthy and are expensive in the quantities required to have a measurable impact on air quality. They are pretty though and if you have the time and the room for them they definitely are worth having but $ for $ if your goal is clean air technology is far more efficient.

beerandt 6y ago

Call a pro. AC systems are not DIY. The things you're looking for exist (and are often mandatory) in the commercial/ non-residential market, but they are not IoT, and they aren't cheap. For instance, most commercial spaces have a MAX value on percentage of recycled air; a minimum amount of air fed into the return must be fresh air drawn from outside. >should be able to cheaply add networked sensors, fans, filters, and vents Sensors can be ok... But your homes's AC design, even if based on simple building code lookups, is based on some fairy complex engineering which rely on certain assumptions. If those assumptions aren't met, the design usually must be approved by a licensed engineer. This is why you don't see more independently controlled vents on the market. No professional is going to install products that don't meet code, unless an engineer has stamped the plans. (Which includes operational logic.) Ignoring regulations, you shouldn't just add controlled vents to a system (or manually close existing vents) without compensating for that elsewhere. You likely need a variable speed blower, controlled/compensated return air flow, and system logic to control it all. Will the house blow up if you install them yourself? Probably not. But it could result in a system operating much less efficiently, increase the number of system cycles (reducing system lifetime), cause duct ruptures/leaks due to increased back pressure, and most likely, cause condensation in places other than the condenser, possibly causing mold to grow and/or rot. Which leaves 2 options: installing a commercial system with the integrated vent control you're looking for, or adding sensors for input for when the system should run, without modification. Biggest simple change you can make for immediate impact? Change your filters every month, even if it means using 12 $3 fiberglass filters instead of 1 $36 hepa filter. For instance, I run a list of room temps through a simple max function to ensure my AC and/or blower runs until the hottest room falls below the set temperature. If this results in wildly unbalanced temps throughout the house, you have a bigger issue, and likely need your system resized/adjusted by a professional. Related, and because most people don't realize it, your AC is an engine. You want it properly sized and to run constant, when needed. Think of your car: is it more efficient to make a trip by many intermittent 100mph sprints, or driving 55mph without stopping. Multi stage compressors now act like car transmissions to dynamically "size" the system as needed, but run constantly with minimal stopping.

jacquesm 6y ago
This is all spot on. The engineering that goes into HVAC systems is under appreciated. When messed up the system that is supposed to give you fresh air can easily become a source of pathogens. You also want filters on ingress and egress (to ensure critters don't have a path into your house), and you want to have a nice fat overdimensioned heat exchanger between the two airstreams to ensure that you're not heating the world instead of your house. +1 on the rapid change of filters, much better to change a filter frequently even if it is a bit lower performance than to let one sit for too long, but keep an eye on your electricity cost, that is the factor that should decide the quality filter that you purchase and frequently you replace it. Ground rule: the better the filter, the more it will absorb, the better the chances that something you really don't want lodges there and starts spreading if the filter gets overloaded. Fiberglass filters are a good compromise between energy efficiency and cost, they have excellent working surface compared to their physical size and tend to have a relatively long working life before they 'join the other side' and become a source of contaminants rather than a filter of contaminants.

Chris2048 6y ago

> IoT should really deliver the goods IOT is a signal for "large disposable income", so HEPA/health anything associated with IoT will bump up the price tag considerably. Why would anyone deliver anything good when people already willingly paying for crap?

AndyMcConachie 6y ago

I went down the rabbit hole of air quality testing devices a couple years ago. The bottom line, AFAICT, it is not easy to accurately test air quality cheaply. Whenever I would find a device that claimed to test air quality I would find reviews by people who were testing that device that stated either; It came miscalibrated from the factory. OR After a short period it would no longer be calibrated. Turns out keeping an air quality testing device calibrated properly is really really hard, and definitely not cheap. So maybe the computing side of this is not really all the difficult, but the physical measurement side of this is absolutely not easy. Eventually I gave up trying to find a device for my home because I realized I would have to really dig into the science hard, and I would have to spend more money than I was willing. And I was unwilling to do either.

jschwartzi 6y ago
I've not worked specifically with contaminant sensors, but I know oxygen sensors require very specific and very consistent flow rates across the element. The type I've worked with used a ceramic element which absorbs oxygen and changes resistance as a result. So increased or decreased oxygen results in increased or decreased resistance. Using a sensor like this to measure percent of oxygen in a gas requires you to eliminate a lot of confounding effects like pressure waves, flow changes, etc.. Basically you can cause the sensor to absorb more oxygen than is present in the gas by temporarily increasing flow. So if you're building an air quality sensor you have to pay very close attention to how the air moves through the sensor. That requires not just a calibration but also characterization of the flow through the system under environmental conditions. One other effect I could see is a contaminant sensor becoming fouled. Oxygen sensors can become fouled and report inaccurate values, which is why it's very important to control the inputs. This is one of the reasons an antifreeze leak in an engine block can cause your engine performance to go to crap. The oxygen sensor is part of how a stoichiometric ratio of fuel and air is maintained, by monitoring the combustion products for excess oxygen. So when it gets fouled either the ceramic element is damaged or the sensor stops receiving consistent flow and the resistance relationship ceases to be valid. In short I don't see how you could build a useful long-lasting sensor by just buying parts off Amazon or Digikey and throwing them together. You would have to treat it like a scientific instrument, meaning that you have to validate your assumptions about how the sensor performs and I doubt that most of the products on Amazon do that.

Diederich 6y ago

Hey there...I appreciate your comment. > I started putting HEPA air filters all over my house Can you very briefly say how you accomplished this? Was it with modified box fans? Thank you!

jcims 6y ago
Just a plug for Coway Airmega. I bought the 400, which is expensive, but it was for someone with health issues. I absolutely love it. Super quiet on low speeds and has been about as low maintenance as one could expect. Filters seem to be of exceptionally high quality and overall build is great.
nawgz 6y ago
I did this - I just bought things off Amazon. Bissell air220 chunks through most of my apartment, and a couple small ones sit in the "leaf node" rooms
Alex3917 6y ago
Just buy one and plug it in: https://www.nytimes.com/wirecutter/reviews/best-air-purifier/ https://www.nytimes.com/wirecutter/reviews/best-air-purifier...
pbronez 6y ago
I purchased several stand-alone Air Purifier appliances for something like $100-200 each [0]. They have two kinds of filters that work in tandem, you replace one every month and the other every three months. It gets expensive to replace all the filters when you have several of them, but they pull a ton of junk out of the air. [0] https://www.winixamerica.com/product/5300-2/ https://www.winixamerica.com/product/5300-2/
Raphmedia 6y ago
Several people have recommend you air purifiers. I would add one thing, look at the price of replacement filters. Air filters are similar to printers in a way. You become tied to a company and have to buy replacement pieces every year or so. Some have bad track record (quick device depreciation because of out of stock filters, etc.)

Nacdor 6y ago

> I noticed a substantial improvement in my health when I started putting HEPA air filters all over my house, and another jump when I moved away from a major road. Same for me when I moved out of a stuffy old high-rise in Philadelphia. I had frequent coughs and wheezing, shortness of breath, and just lots of general discomfort with breathing. Every time I washed my car there was a thick black layer of soot covering it within a couple days, so I'm sure that was doing great things for my lungs. Also got a couple serious colds every year when I lived there. That was as a 20-something who never smoked, didn't have asthma and wasn't overweight. Living in the suburbs now and haven't had an issue since moving.

kaitai 6y ago
Air quality and health are quite significant in predicting COVID mortality on a neighborhood by neighborhood basis, too. Environmental air quality -- socioeconomic status -- health outcomes (and more) are tied in a very complex network with a lot of reinforcing cycles. I don't know what the distribution of stove type by income level is, but I do have the impression that richer Americans are more likely to have fancy induction ranges, and poorer Americans are more likely to use gas. Annoying as I certainly find gas more pleasant to cook with.
- supertrope 6y ago
  When I think of a cheap apartment I imagine a stove with electric resistive coils.
  - phil21 6y ago
    Indeed. The only rentals with gas stoves are either the high-end market, or legacy housing stock probably 50+ years old. Any lower/middle class oriented apartments I've seen built in the past 30 years in my area at least have all been electric. Also spent a lot of my 20's in cheap apartments, and never had anything more than an electric coil stove.
    - jdhn 6y ago

0xbadcafebee 6y ago

> It seems like this is an area where IoT should really deliver the goods. I should be able to cheaply add networked sensors I think you're going the wrong way. These problems were caused by trying to artificially exert control over a complex environment. Similar to trying to "manage" a natural environment, each effort results in 2 more side-effects which each then need their own "management". On the other hand, some modern "management" techniques are to simply re-introduce nature to an environment and letting it self-manage. This ends up with better ecological health as well as less cost and complexity. But we have to let go of whatever weird human-specific desire caused us to mismanage it the first time. Why do we need carbon monoxide monitors? Because carbon monoxide builds up, because gas-powered devices and heat exchangers live inside the sealed home. Put them outside the home and the problem is solved, no technological solutions necessary. A properly designed home can also avoid things like vapor barriers, reduce dependence on air conditioning and heating, avoid mold and mildew, and require less maintenance. But if we insist on working within existing home designs, there's a constant requirement for new fixes for the new problems we introduce.

briefcomment 6y ago
This is a great idea. Do you know of any further reading on fundamentally redesigning housing in practical ways?
- 0xbadcafebee 6y ago
  Sadly I don't have reading suggestions. I've kind of gathered details over time. My own "redesign" is just to look at how homes used to work. Wattle and daub, hogan, pueblo, timber frame, log cabin, long house, clochán, crannog, igloo, walpini, adobe, brick. They each have pros and cons, but they work best for where they were built and the needs of the people that lived there. They adapted solutions for heating/cooling, pest control, weather resistance, cooking, storage, etc that fit their purpose. As far as I know, none of these homes ever had to deal with annoyances like mold or carbon monoxide. But then again the downsides could be severe in densely-populated urban areas; entire cities could be razed overnight by fire and strong winds! Before modern homes were redesigned to take advantage of supply chain efficiencies, timber frame and stone foundation were common in the US. Before air conditioning, homes were designed for where they sat to take the seasons into account. A central corridor of air could be funneled by opening doors or windows on either side of the house, rapidly cooling or heating it, and windows and shutters could lock in whatever the temperature was - but this would be a bad idea on a humid day! A stone foundation acted as a mini thermal battery, and some building materials were incredibly good insulators. Also common were fireplaces and living quarters in the center of the home; shut all the doors to keep your room toasty warm, or open them up to warm the house for company. There was no vapor barrier, no sheeting; just nail some shingles to the frame and stuff whatever you can into the walls for insulation, or build walls out of a composite like mud and stick. In wet, hot areas, you had lots of porches and big awnings so you could stay outside with a fan in the shade. There's many other old-school techniques we could be using, but then homes become more expensive as no contractor knows how to build them, or we've literally done away with all the natural resources and now they have to be acquired at great expense. Not to mention of course, zoning might have made it all illegal anyway. In many ways we've engineered ourselves into a corner.

Aardwolf 6y ago

> It seems like this is an area where IoT should really deliver the goods. A combination of sensors and actuators to fix the air problem, yes. But where does the internet come into play here? Seems like something 100% local to me. Except if you want to view the data remotely, but that's a side feature, not a main requirement for this to work.

0xffff2 6y ago
I think it comes into play because LANoT doesn't roll off the tongue the way IoT does.
- deleted 6y ago
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turtlebits 6y ago

I have an Awair unit and it's fairly inexpensive. I can't vouch for the accuracy, but I saw DHH post about it and compare it other consumer sensors and more "professional" sensors and he recommended it. One of the main problems is that homes are not built for indoor air quality. Furnaces in crawl spaces or garages, lack of air sealing. You can't just add sensors and fans to fix the problem. Plus, adding a fan/vent to a home isn't ever going to be cheap. You're talking about cutting the interior and exterior of your house, running ducting and wiring up electrical.

Raphmedia 6y ago
> I have an Awair unit and it's fairly inexpensive. I have an anecdote about the Awair. The air at one of my previous workplace was making me sick, so I asked the management to look at the air quality. They hired a professional who saw nothing - because they asked for the AC to be turned off during the monitoring. I got an Awair and managed to track when the air quality dropped. It was whenever the AC came on. They then called another professional who finally caught it -- turns out the building's ventilation ducts had not been cleaned in 5 years AND there was water damage. Without a customer grade air quality tracker, I would have simply believed the first professional. I would have had to either suffer being sick daily at work or having to quit for air quality reason. Now I carry mine around to my friends and family's house and let them borrow it for a while. It always come up with explanations about issues people had been quietly enduring forever.
- s5300 6y ago
  Hi - can you tell me the model you bought?
  - Raphmedia 6y ago
    I have the Awair 2nd Edition. It is similar to the Awair Element. However, as I don't have a smart home I sometime wish I had an Awair Glow C instead (disclaimer, it does not have as many sensors). It's a smart plug, so it can turn off the device you plug into it... I would plug my air purifier or maybe my air humidifier to it. If you want to use one suche device on the go, at friends places, etc., I'd recommend the Atmotube Plus or Atmotube Pro by Atmotube (depending on your needs). My purchase was a few years ago now. I've heard that the market is bigger now, so you may want to shop around. I also have the big Dyson purifier at home which comes with built-in sensors.

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