9 ms·

I think the draftiness is key. In my findings, in a "modern" house (double-paned windows, built in the last 20 years), sleeping with the door closed will spike

I think the draftiness is key. In my findings, in a "modern" house (double-paned windows, built in the last 20 years), sleeping with the door closed will spike CO2 to 4 digits. The other thing is that air really needs to circulate in order to lower CO2 - opening a window in a room will not lower the hallway CO2 unless there's at least some draft / air movement.

5e92cb50239222b 5y ago
Temperature difference helps if there's no wind. In winter time CO₂ drops from 4000+ ppm to ~450 in only a couple of minutes after opening a single window (with inside to outside temperature difference of 50°C or higher). In summer it drops to ~600-700 and stays there, and even this takes hours.
- y4mi 5y ago
  50°C difference or even higher? Damn mate, even Siberia only gets around -34°C which is less then that of you target the usual 18-21°C. Your winters sound terrifying.
  - theluketowers 5y ago
    Saskatchewan Canada can easily reach -40°C for several weeks during the winter.
    - JamisonM 5y ago
      What? Maybe in the most northern reaches.. even then "for several weeks" is a stretch.. even Uranium City doesn't hit -40°C every winter!
      - bbarnett 5y ago
        There is often confusion between wind chill, and actual temps. But the parent is not inaccurate, for they did not mention "each year". Even 10 minutes North of Ottawa, I saw -42C, real, not just windchill, for a week, about a decade ago.
  - freeopinion 5y ago
    Winters? I thought they were referring to this last May or the previous August. https://en.wikipedia.org/wiki/Highest_temperature_recorded_on_Earth#Unverified_claims https://en.wikipedia.org/wiki/Highest_temperature_recorded_o...
    - y4mi 5y ago
      He specifically said winter but having 68-74°C at minimum sounds terrifying too, honestly
- crazygringo 5y ago
  That's what I've discovered over the past year! I live in NYC and my CO2 levels are fine in both the winter and on hot summer days, without even trying. But when it's 65-75°F outside in the spring/fall... CO2 builds up in my apartment like crazy. I keep the windows open and my bathroom fan on to try to suck fresh air in... but even so can't manage to really get it below 650, and with just a window cracked it sticks around 850. It's really frustrating.
davemp 5y ago
That's why an ERV [1] is important in a modern house with good air tightness. [1]: https://en.wikipedia.org/wiki/Energy_recovery_ventilation https://en.wikipedia.org/wiki/Energy_recovery_ventilation
nsporillo 5y ago
In a modern home, there should be supply and return vents in every room. My home built in 1978 has 3 returns for the entire house, one on each floor. Master bedroom has a supply, but the return is located in the hallway. Over the years, the recommended door cut to allow air flow has been changed (presumably for greater privacy) - which leads to the scenario you're describing. I could add the door cut back in, install return transfer grill, or look into adding a secondary heat recovery ventilator that acts independently of the primary HVAC system.
- geerlingguy 5y ago
  I know many people who put 'draft stop' devices on the bottoms of their bedroom doors in older homes (old enough to not have returns in each room, but new enough for central air), not realizing they're cutting off the one bit of circulation they need for a proper functioning central air system! Or they buy new high efficiency windows and doors, and that 'tightens up' the house, but they don't also install an HRV (Heat Recovery Ventilator) to exchange outside air.
  - nsporillo 5y ago
    Realistically new windows and doors probably wont drop the homes air changes per hour below the recommended minimums, but I don't know for sure. I've gotten my crawlspace spray foamed and I'm getting my vented attic spray foamed to bring it into my envelope. Also getting new windows and doors soon, but after all of that I think enough air could leak through sill and top plates, electrical outlets, etc. Having the foam crew do a blower door test for free if we go with them, so I guess I'll see. I live in climate zone 5a (cool, humid) so historically natural ventilation was used via induced pressure differentials generated by mechanical means (dryer, furnace, bathroom and kitchen vents). When we get new furnace and water heater that pull combustion air from outside, we're left with mostly manual means for generating negative pressure that drives infiltration. (But also wind, and pressure differentials caused by temperatures in winter) In our case, we're definitely considering either an HRV or ERV to supply fresh outdoor air that we control (input and output CFM, MERV #). Our indoor air quality is poor enough to the point where we live with the tangible symptoms (Rhinitis), not just numbers on a sensor. For those with interest in these topics, I suggest skimming a copy of one of the ASHRAE fundamentals handbooks[1]. It reads as a textbook but has incredible depth into the physical sciences that relate to building science, heating, cooling, and ventilation. [1] https://archive.org/details/ashraehandbook2017hvacfundamentalssi/page/n7/mode/2up https://archive.org/details/ashraehandbook2017hvacfundamenta...
withinrafael 5y ago
Our multi-room apartment in Redmond, WA, has an always running intake fan in the master bathroom advertised as a way to keep air fresh. I always wonder how effective that really is (at apartment scale) and if it's really worth the 24/7 power draw.
- asdff 5y ago
  Probably more for preventing mold damage from lazy tenants I imagine.
- hourislate 5y ago
  It's to keep positive pressure in your unit for safety purposes. If there is a fire the fresh air will help keep smoke out of your unit and as a bonus it keeps other building odors out. Generally it is a large fan on the roof that just sucks air down a stack pumping it into every unit. You could put a filter over the register and filter that air.
  - withinrafael 5y ago
    Sorry, by intake I meant it's sucking air in. That is, air is leaving my apartment. I think you're on the right track with the safety angle here though. Will do more research.
    - bbarnett 5y ago
      Air is leaving, thus, it is being sucked out of the apartment.
  - zz865 5y ago
    Its probably the opposite, it sucks out air. It does stop smells from this apartment going into neighboring spaces.
- velosol 5y ago
  Almost certainly designed to ASHRAE 62.2's specs so that you get enough ventilation through a combination of infiltration (leakage) and additional mechanical ventilation. It's certainly worth it and if designed as a continuous ventilation fan should be one of the lower (~15W) draw units. Not sure how to really measure effectiveness other than by trusting in the experts who came up with the spec and air quality as an indirect measure. https://homes.lbl.gov/ventilate-right/step-3-whole-building-ventilation-rate https://homes.lbl.gov/ventilate-right/step-3-whole-building-...
dghughes 5y ago
I bought my parents a Netatmo weather setup. The one in the house measures temp, CO2 and the one outside temp, humidity. During Christmas Day visits with only a half dozen people the room CO2 spiked to over 1,000ppm. Older house from the 1970s no HVAC. Opening a window (cross draft) brought it down to 300ppm. The room was stuffy before and great after so it shows how sensitive we humans are to air quality.

5e92cb50239222b 5y ago

Temperature difference helps if there's no wind. In winter time CO₂ drops from 4000+ ppm to ~450 in only a couple of minutes after opening a single window (with inside to outside temperature difference of 50°C or higher). In summer it drops to ~600-700 and stays there, and even this takes hours.

y4mi 5y ago
50°C difference or even higher? Damn mate, even Siberia only gets around -34°C which is less then that of you target the usual 18-21°C. Your winters sound terrifying.
- theluketowers 5y ago
  Saskatchewan Canada can easily reach -40°C for several weeks during the winter.
  - JamisonM 5y ago
    What? Maybe in the most northern reaches.. even then "for several weeks" is a stretch.. even Uranium City doesn't hit -40°C every winter!
    - bbarnett 5y ago
      There is often confusion between wind chill, and actual temps. But the parent is not inaccurate, for they did not mention "each year". Even 10 minutes North of Ottawa, I saw -42C, real, not just windchill, for a week, about a decade ago.
- freeopinion 5y ago
  Winters? I thought they were referring to this last May or the previous August. https://en.wikipedia.org/wiki/Highest_temperature_recorded_on_Earth#Unverified_claims https://en.wikipedia.org/wiki/Highest_temperature_recorded_o...
  - y4mi 5y ago
    He specifically said winter but having 68-74°C at minimum sounds terrifying too, honestly
crazygringo 5y ago
That's what I've discovered over the past year! I live in NYC and my CO2 levels are fine in both the winter and on hot summer days, without even trying. But when it's 65-75°F outside in the spring/fall... CO2 builds up in my apartment like crazy. I keep the windows open and my bathroom fan on to try to suck fresh air in... but even so can't manage to really get it below 650, and with just a window cracked it sticks around 850. It's really frustrating.

davemp 5y ago

That's why an ERV [1] is important in a modern house with good air tightness. [1]: https://en.wikipedia.org/wiki/Energy_recovery_ventilation https://en.wikipedia.org/wiki/Energy_recovery_ventilation

nsporillo 5y ago

In a modern home, there should be supply and return vents in every room. My home built in 1978 has 3 returns for the entire house, one on each floor. Master bedroom has a supply, but the return is located in the hallway. Over the years, the recommended door cut to allow air flow has been changed (presumably for greater privacy) - which leads to the scenario you're describing. I could add the door cut back in, install return transfer grill, or look into adding a secondary heat recovery ventilator that acts independently of the primary HVAC system.

geerlingguy 5y ago
I know many people who put 'draft stop' devices on the bottoms of their bedroom doors in older homes (old enough to not have returns in each room, but new enough for central air), not realizing they're cutting off the one bit of circulation they need for a proper functioning central air system! Or they buy new high efficiency windows and doors, and that 'tightens up' the house, but they don't also install an HRV (Heat Recovery Ventilator) to exchange outside air.
- nsporillo 5y ago
  Realistically new windows and doors probably wont drop the homes air changes per hour below the recommended minimums, but I don't know for sure. I've gotten my crawlspace spray foamed and I'm getting my vented attic spray foamed to bring it into my envelope. Also getting new windows and doors soon, but after all of that I think enough air could leak through sill and top plates, electrical outlets, etc. Having the foam crew do a blower door test for free if we go with them, so I guess I'll see. I live in climate zone 5a (cool, humid) so historically natural ventilation was used via induced pressure differentials generated by mechanical means (dryer, furnace, bathroom and kitchen vents). When we get new furnace and water heater that pull combustion air from outside, we're left with mostly manual means for generating negative pressure that drives infiltration. (But also wind, and pressure differentials caused by temperatures in winter) In our case, we're definitely considering either an HRV or ERV to supply fresh outdoor air that we control (input and output CFM, MERV #). Our indoor air quality is poor enough to the point where we live with the tangible symptoms (Rhinitis), not just numbers on a sensor. For those with interest in these topics, I suggest skimming a copy of one of the ASHRAE fundamentals handbooks[1]. It reads as a textbook but has incredible depth into the physical sciences that relate to building science, heating, cooling, and ventilation. [1] https://archive.org/details/ashraehandbook2017hvacfundamentalssi/page/n7/mode/2up https://archive.org/details/ashraehandbook2017hvacfundamenta...

withinrafael 5y ago

Our multi-room apartment in Redmond, WA, has an always running intake fan in the master bathroom advertised as a way to keep air fresh. I always wonder how effective that really is (at apartment scale) and if it's really worth the 24/7 power draw.

asdff 5y ago
Probably more for preventing mold damage from lazy tenants I imagine.
hourislate 5y ago
It's to keep positive pressure in your unit for safety purposes. If there is a fire the fresh air will help keep smoke out of your unit and as a bonus it keeps other building odors out. Generally it is a large fan on the roof that just sucks air down a stack pumping it into every unit. You could put a filter over the register and filter that air.
- withinrafael 5y ago
  Sorry, by intake I meant it's sucking air in. That is, air is leaving my apartment. I think you're on the right track with the safety angle here though. Will do more research.
  - bbarnett 5y ago
    Air is leaving, thus, it is being sucked out of the apartment.
- zz865 5y ago
  Its probably the opposite, it sucks out air. It does stop smells from this apartment going into neighboring spaces.
velosol 5y ago
Almost certainly designed to ASHRAE 62.2's specs so that you get enough ventilation through a combination of infiltration (leakage) and additional mechanical ventilation. It's certainly worth it and if designed as a continuous ventilation fan should be one of the lower (~15W) draw units. Not sure how to really measure effectiveness other than by trusting in the experts who came up with the spec and air quality as an indirect measure. https://homes.lbl.gov/ventilate-right/step-3-whole-building-ventilation-rate https://homes.lbl.gov/ventilate-right/step-3-whole-building-...

dghughes 5y ago

I bought my parents a Netatmo weather setup. The one in the house measures temp, CO2 and the one outside temp, humidity. During Christmas Day visits with only a half dozen people the room CO2 spiked to over 1,000ppm. Older house from the 1970s no HVAC. Opening a window (cross draft) brought it down to 300ppm. The room was stuffy before and great after so it shows how sensitive we humans are to air quality.