Comment by UniverseHacker
6 hours ago
I think it’s little appreciated that high CO2 levels cause cognitive impairment, and with the same amount of (often very poor) air exchange, higher outdoor concentrations can push indoor spaces to levels that cause impaired cognition and poor sleep. I’ve already been seeing this in my home, and will often open windows even when cold just to keep co2 levels reasonable. One solution that can help is an external air heat exchanger, which can exchange air with the outdoors without compromising your homes heating and cooling like an open window will do.
Noticeable cognitive impairment starts in the 700-1000ppm range, whereas it is very common for homes to reach 2000-3000ppm, especially when in a closed bedroom.
> Noticeable cognitive impairment starts in the 700-1000ppm range
The US navy failed to detect such effects in submarine crew, even at much higher levels like 10,000 ppm.
Another reason to be skeptical is that exhaled breath is 4% CO2 (40,000 ppm!). Therefore a few thousand extra ppm in the inhaled air should not make much of a difference to the homeostasis mechanisms in our bodies.
See my sibling comment for meta-analysis that disagrees with you. Would love to see citation for those navy experiments.
Back in the 00’s I worked at a place where we were still ignoring WLB and would work until seven a couple nights a week on average. But the building AC shut off at 6. A few of us noticed that the later it got the worse our decisions and the worse the bickering and we eventually got to the policy that anyone could declare Deciding done for the evening when they realized we were just tired, hot, and stuffy. Every minute past about 6:15 got worse, particularly in summer.
I’m sure the CO2 was part of it but lack of circulation also means increasing temperature, especially with a bunch of people in a small meeting room. Long meetings themselves are a problem and any excuse to call it early is probably worth it even if it’s not entirely true.
Citation for a 2018 study with submarine-qualified sailors: https://pubmed.ncbi.nlm.nih.gov/29789085/
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>One solution that can help is an external air heat exchanger
I have one of those, it blows fresh air in through the bedroom and sucks it back out through the kitchen (loft house, this route prevents food smells from wafting into the bedroom). Aside from just feeling fresh all year, this system also prevents mosquitoes from entering in summer while still allowing air circulation, it automatically bypasses the exchanger at night to provide cool air and it has some pollen filters installed which helps with hay fever.
So great economic return and a bunch of upsides, but it does require space for the exchanger and the ducts throughout the house.
This. I have that type (regenerative MHVR) installed in the attic for upstairs, and a synced pair of in-wall ceramic (recuperative) types on opposite sides of main living area downstairs (eliminating ducting, albeit with reduced efficiency). I haven't attempted any energy/ROI calculations but fresh filtered air, lower humidity and good nights sleep are well worth the claimed single-digit watt power usage to me.
I suspect bathrooms aren't big enough to buffer the air pressure but it seems like we should design the air handling so the “fan” is always on in the bathrooms. Maybe a split between several places and taking a bit from the cold air return for the rest.
The system is always on and moving air as a whole, and the water closet and bathroom have an intake duct that sucks in humid air that goes to the heat exchanger for exhaust. I have a little humidity sensor hooked up to Home Assistant that kicks the fan in the exchanger into a higher gear and returns to auto when humidity returns to baseline.
All rooms in the house have an intake or exhaust duct depending on requirements.
There is also a small control panel next to the thermostat in the living room that controls the whole system for when, ahem, your number two's are particularly odorous (or you're using the kitchen to cook for 6).
I have been monitoring for high CO2 for a few months now. I easily find myself in the 1000 - 1400 range for some time before I finally let some air in in winter.
I have not noticed significant cognitive impairment (not saying it did not happen)
My quality of sleep/life have greatly increased since installing an Energy Recovery Vent (ERV) — it exchanges outside/inside air through a membrane, which is about 60-80% efficient for both humidity and temperature re-capture (depending on fan speed).
[•] <https://en.wikipedia.org/wiki/Heat_recovery_ventilation#Ener...>
I use a Panasonic model — readily available from Big Box Retail (~$700 + $100 in vent/conduit) — which can do 20 - 60 cfm (in my 900 sqft home this can easiliy exchange the entire volume several times per day).
> higher outdoor concentrations can push indoor spaces to levels that cause impaired cognition
I am somewhat skeptical of this:
https://www.astralcodexten.com/p/eight-hundred-slightly-pois...
This is a meme on hacker news that's usually stated as a fact, but I'm not sure there's any robust evidence of cognitive impairment at <1000ppm
https://www.sciencedirect.com/science/article/pii/S036013232...
> In this study, a systematic review and meta-analysis of fifteen eligible studies was performed to quantify the effects of short-term CO2 exposure on cognitive task performance.
> The complex task performance declined significantly when exposed to additional CO2 concentrations of 1000–1500 ppm and 1500–3000 ppm
It looks like there might be a very small effect starting at around 1000ppm but so small that many studies find no difference at all, and reliable effects are only noted at 3000ppm or more.
So we're a long way from needing to scrub co2 from the atmosphere to get any work done
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Additional
> I think it’s little appreciated that high CO2 levels cause cognitive impairment
Have you been telling representatives? Here's a letter I wrote to mine:
https://pdfhost.io/v/bRJEGptatL_climate-change
Really? Wow, I try to keep my place at 500-600, without that much effort.
I find it extremely unlikely that homes are routinely at 2000-3000 ppm. That is extremely high and would mean multiple people in a small area with no air exchange for a long while.
I monitor my indoor co2, but don't take any action because it's extremely rare to be above 700 or 800. I can only remember a handful of times its reached 1k ppm. And my house should be prime candidate for co2, it was built during the era of "seal all air gaps" but before ERV or HRVs. I also use pressurized co2 to inject co2 into a planted aquarium. And my dogs are terrified of open windows so they are rarely open.
It happens a lot in efficient houses that don't cover all bases with HVAC (the vast majority of recently built houses), where the room door is closed, maybe the vents are not ideal, and there is usually no makeup air or forced air ventilation other than a furnace intake.
This change in scientific literature actually causes a ~quadrupling of recommended airflow ratios for tight homes versus ASHRAE's previous guidelines, putting strong emphasis on an ERV. Previously, ventilation needs tended to be dominated by air quality and smell, by humidity buildup, or by theoretical house parties that maxed out the system.
This ventilation adds capital expense, but it's substantially more controllable and significantly cheaper in the long run in colder climates than 'just open a window' or 'just don't build the house so tightly sealed'. Reserve the operable window for the aforementioned house party, which is out of a reasonable design envelope.
Homes in the upper midwest are well-sealed and insulated. Bedrooms can hit 2,000 ppm with two adults sleeping in them.
My bedroom regularly gets to 3000 at night, and the flat in general is around 2000. This is in the winter, when I don't open the windows for days because of the cold. The flat is very well insulated.
If we are three in my small living room in winter (around 20m2), it easily climbs above to 2000ppm in less than an hour
Ok this sounds like BS, what kind of sensor is being used to get such readings? What do you use?
I used an Awair Element after wondering if Co2 buildup was causing my groggieness in the morning and an ever so slight dull headache.
My bedroom was quite small at the time, but I measured the same effect of buildup in a larger bedroom, just the Co2 level took a little longer to reach it's peak.
In the small room it took about 45 mins to climb to about 1400 after I closed the door and went to sleep.
I'm currently trying to install some above-door vents to improve circulation but this is a topic most people don't consider at all, even though studies have shown the effects of classrooms having high Co2 concentrations on exam results and cognition.
We monitor air data quite closely at work.
CO2 rises really fast with people in even a large space.
I wouldn’t put too much effort into vents above a door as we’ve seen that CO2 will leak through doors and even floors/ceilings very quickly.
When was it calibrated?
> high CO2 levels cause cognitive impairment
Sounds seriously unlikely. How would this work in practice, at the level of bodily functions?
I don't know the mechanism, but: https://www.google.com/search?q=co2+cognitive+impairment