> "Exposure to CO2 and VOCs at levels found in conventional office buildings was associated with lower cognitive scores than those associated with levels of these compounds found in a Green building." – Allen et al 2016. The effect seems to kick in at around 1,000 ppm of CO2.
The last time this came up I bought a CO2 meter for my office. I was quite surprised how often it went over 1,000. Outside air runs around 450.
I increased the duty cycle of the house fan, and open a window when it reaches 800. Right now I'm at 505.
In the comments on that lesswrong post from a few years back, you raised a good question that is perhaps easily answered:
it has the same issue as Kurzban's blood-glucose/willpower
criticism: if the brain needs more oxygen than it's getting
why doesn't one simply breath a little more? While sedentary
during these sorts of tasks, you have far more breathing
capacity than you should need
Seems quite likely (or at least very possible) that we've outpaced evolution here, right?
Prior to the industrial revolution, seems our bodies would never have needed to adapt to a rapid spike in environmental CO2 levels. Our brains are necessarily good at signaling the body when they need more oxygen; they're not necessarily good at realizing when they're dealing with other issues they're not adapted to react to.
I believe there may be a common misunderstanding the relationship between CO2 levels and oxygen in one's body, at least as it was explained to me by doctors during my mom's struggles with COPD.
Blood oxygen saturation levels and CO2 levels are not inversely correlated. One of the problems with late-stage COPD and reduced lung function is that while it's relatively easy to get a person's oxygen levels up (just administer oxygen!) they still suffer the effects of excess CO2 in the blood. A late stage COPD sufferer can have > 95% O2 saturation in their bloodstream and still suffer the other effects (including cognitive issues) that result from the excess CO2.
(Apologies for responding you wrote four years ago)
Thanks for these links Gwern, down the rabbit hole I go.
But how would you summarize the situation? Is it that there's not a definite study that proves the whole thing?
One of the big trends in green/sustainable building is creating relatively air tight buildings in order to cut down on heating and cooling costs (see: Passiv Haus, Passive House, Pretty Good House). In order to do that, though, mechanical ventilation is needed. As a result, Heat-Recovery Ventilation & Enthalpy-Recovery Ventilation residential units can be installed for only $2k-$4K. Seems like a worthwhile investment (for when it’s not convenient or possible to open a window).
I live in a relatively new apartment building that has heat recovery system installed in all apartments by default. My apartment is 73sqm, the ventilation unit is rated at 300m3/h. The building is located in a busy part of town with lots of traffic around. The city has a humid continental climate (Dfb) so it does get pretty cold during winter.
It does help a lot and I couldn't imagine living without it.
- Removes CO2 - averages ~650ppm in all rooms, almost never goes higher than 1000ppm (3 person household).
- Retains up to 85% of heat (based on the specs) using the exchanger, but also has an active electric heater inside that can be turned on in winter for ultimate comfort.
- Removes moisture from the bathroom and kitchen and dumps it into the drain via a separate drain pipe.
- Isolates from the outside noise as you can keep your windows closed shut all the time.
It does have some drawbacks however:
- Up to +6dB noise in rooms when running at full power (I run it at 20% at night which only adds ~+1dB).
- F7 class filters need to be changed every 3-6 months (~50€).
- Air intake grill with a pre-filter mesh needs thorough cleaning every 6-12 months as it usually gets clogged with debris in spring and autumn.
Not sure if it's due to these drawbacks or lack of knowledge lots of residents don't actually use their unit. You can tell by the open windows all year round. Most say it's too noisy for them - most probably due to lack of maintenance. Others are just plain ignorant saying opening windows is the only way to get "fresh air".
The other upside to sealing plus mechanical ventilation (instead of leaky-building ventilation) is that your building is always fresh. Leak-driven ventilation leads to a building that is drafty on windy days and stuffy on calm days.
Plus if the leaks involve air circulating though insulation in the cavity or attic, whatever is in there will end up in your house air. That could be dust from construction, parts of the insulation material, or decomposing rodents.
Is the 3 months interval a regional thing, or based on the heat exchanger? Mine have 1 year intervals, and with a subscription for filters it is easy to remember to change the filters
>Is the 3 months interval a regional thing, or based on the heat exchanger?
both. That is it varies between different units but also varies with local conditions, if your local conditions are "heavy-duty" (very high humidity, smog, area with lots of dust or lots of pollens etc.) you should consider replacing more frequently than rated intervals.
Trouble with passive houses is a) people open windows. b) hate fan noise. c) the designs are brittle and prone to catastrophic failure. d) energy consumption isn't going to an issue over the life of the building. e) In Europe and North America the replacement rate for housing is in the low single digits.
And f) most passive house designs have humidity/mold issues down the road, unless proper and frequent maintenance is done. (I've read about passiv haus and similar a while back).
There is a slow moving disaster in the Midwest where houses constructed in the last 25 years are rotting from the inside due to leaks and internal condensation. Problems are. Sealed construction means moisture can't escape. Think insulation hides problems until major damage occurs.
I'm also skeptical because houses we build today should be in use a 100 years from now. And it's really obvious that renewables aren't supply limited like oil and gas. But in the passive house world it's always 1980.
We built a ton of them here in Sweden, but the name escapes me. They were marketed with being able to last for 'at least 20 years' when being built, which should have been a warning sign not to spend $1m on for it on a <$100k family income.
If we relax "never" to "not more than 60 days a year", that would be most of Canada, northern US, most of Europe and Russia. No idea what's going on in southern hemisphere, but I guess Argentina/Chile and southern Australia are the same.
This obsession with mold looks to me as an exclusively US thing. I have no first-hand data but I guess it's due to insufficient air flow combined with air conditioners pushing humidity all the way up.
Mold is an issue in Finland,
mostly for insulated houses with poor ventilation. Many schools and public buildings have mold and other air issues due to saving on heating.
Cold climate results in low humidity. If you're mostly heating your home (as opposed to running aircon 24/7), air inside tends to be of lower humidity than outside. So low that it becomes uncomfortable and one has to use humidifiers.
The only place mold has any chance in those conditions are the leak spots on the fridge door seal.
I think the Passiv Haus standard of 0.6 air changes per hour at 50 pascals is kinda nuts, and likely not worth it. The more relaxed "Pretty Good House" goal of 2 ACH is still pretty tight and requires ventilation, but is a bit more forgiving and acknowledges that a moderate amount of electricity for HVAC isn't so hard to come by. The catastrophe with older houses in the Midwest (where I'm from) is that they'll each put out a dozen or more tons of CO2 each winter due to fossil fuel heating.
Regardless, the point is that even if you don't have one of these super-airtight houses, you can still install an HRV/ERV for not a ton of money. I'm considering one for my vacation cabin where the primary heat is a wood stove.
I did the same thing at my office and brought it into a conference room with 7 other people. We watched the CO2 climb to about 900 and then it started going down. Seems the climate control system is also tracking CO2 and it started pushing fresh air in when the level got too high. A nice surprise that we have systems managing this - I don't know how common that is in offices though.
Anecdotal, but I used to work in an IT department where some areas had good, or at least tolerable, ventilation and some very clearly did not. The difference in moods and productivity between teams in each was distinct enough to notice, but, at the time, I don't think anyone would have thought of CO2 levels as a confounding issue.
I learned long ago to not even try to write code when I'm above a certain threshold of tiredness. I just have to tear it all out again after a night's sleep.
I see low CO2 spaces becoming the next big thing for the privileged classes as CO2 levels rise. Weworks of the future will be advertising this as a definite selling point. Mansions with scrubbers getting it down to 200ppm
I recall reading once that the health of poorer people was better one or two hundred years ago because poorer people ate cheap food - i.e. vegetables - rather than a meat-heavy diet.
Opening a window only works up until ambient CO2, which will continue to rise. A scrubbed interior atmosphere is already a selling point during fire season in the Bay Area.
Seriously, I’ve always thought people in Sydney compared to France were taller and healthier because they have more oxygen... Not only they are outdoors often, but they also have less stuffy buildings. Classrooms in France are the epitome of “stuffy”, and it’s frequent for me to leave a theater because there is 400 people and the vents are off. The usual reaction is to imply I’m sensitive ;)
After watching this Tom Scott video https://www.youtube.com/watch?v=1Nh_vxpycEA I bought this CO2 monitor: https://amazon.com/gp/product/B00MB93CK8 It worked quite well and showed that I don't have anything to worry about. Now I'm trying to pass it on to someone else. I'll be willing to sell it for half price if anyone is interested.
If anyone is interested it seems you can find (more or less reliable) sensor modules for about $20, such as the MH-Z19, and read it from to an arduino or esp.
I put one in my son's bedroom and was blown away. He's 3, and calls me in to sleep with him sometimes. It's a small room, and we keep the doors closed so his sister doesn't wake him up and I was blown away by how high the CO2 got with both of us in there: https://www.reddit.com/r/dataisbeautiful/comments/cek4dm/co%...
What did you use to measure? Unfortunately all the ones I've seen linked here are too expensive for someone like me who doesn't live in America. I wonder if there are cheap ones out there that maybe not so precise but at least measure something.
Does anyone know of a cheap IoT type sensor for CO2? It can be any type, even RasberryPi or Arduino based. I'm not interested in sensors without connectivity options.
About the levels, I'm working on an IoT project and I've seen data from a public school that has heating with radiators (so no real ventilation). One classroom with the sensor would routinely rise above 1000 ppm, with peaks over 3000ppm. Then you'd observe a sudden drop in CO2 level and temperature as they would open up a window. It's insane how high it can get especially if the building lacks proper ventilation.
There are a bunch of raw sensor components that you can connect to an Arduino or Pi. I ended up going with the Sensirion SCD30 but also tested options from Amphenol's Telaire line. Both are pretty easy to communicate with using an Arduino.
I haven't tested an MH-Z19 but that's a popular cheap option.
I have a slightly more capable one but the results are similarly motivating. Right now I'm more concerned with the particulate counts... if 27 is bad, does 120 worse and going outside into 700+ me dumberer?
When I was living in Lakemba this prompted me to rig a HEPA filter outside and run my bedroom at positive pressure. That helped a lot. But I've had to move for work so now I'm renting a cardboard box (ok, technically it's "fibro" on piles with a leaky wooden floor. Outside ~= inside)
I have no real idea, especially because the outside unit is about 10m away and shows ~700ppm. I will try swapping them to see whether it's a calibration issue, but right now the outside unit is at work with me so I can open it up and take photos.,
On the other hand, a paper on 'Effects of Exposure to Carbon Dioxide and Human Bioeffluents on Cognitive Performance' (2015) concludes that 'only exposures to bioeffluents when CO2 reached 3,000 ppm significantly affected performance of some cognitive tasks. Increased arousal level at this exposure can be used to explain the observed results.'.
I'm very sensitive to lack of oxygen in a room. Our office is old and some days they don't run the A/C if it's not hot enough outside, and I feel like I'm suffocating and my productivity suffers.
One of these days I'm going to have to rig up something to start the house fan when the CO2 goes above 800 ppm and I think you'd need a different sensor with a realtime output port for something like that.
Direct feedback is cool, but a simple schedule is really easy & reliable. Even occupancy detection isn't all that critical- nobody wants to come home to a stuffy house, and most people's schedules are very predictable.
These days IoT is so widespread that something like a $25 WeMo smart outlet is hard to beat. Hard wired is "best" but a million times more hassle and more expensive.
The last time this came up I bought a CO2 meter for my office. I was quite surprised how often it went over 1,000. Outside air runs around 450.
I increased the duty cycle of the house fan, and open a window when it reaches 800. Right now I'm at 505.
Buying the meter was a really good investment.