[kylerush]

I recently started measuring CO2, Radon, PM (particulate matter) 1.0, PM 2.5, VOC, humidity, temperature, and air pressure with the Airthings Wave connected device.

I have learned a lot while using it for a couple weeks. First, making a fire in your fireplace is great for ambiance but drags air quality down substantially. It eats up oxygen a lot and make the CO2 increase sharply. It also causes very high spikes in particulate matter (both 1.0 and 2.5 micron) from putting the burned byproducts into the air.

I also started improving the energy efficiency of our heating system by fixing spots in the house where cold air comes in. While this results in less energy used to heat the home, it causes CO2 to increase because there isn’t anymore large holes to bring fresh air in. This device helped me learn that CO2 is and energy efficiency are circular problems. The tighter my house is, the more I need to focus on ventilation - exhaust out and fresh air in. It sounds complicated but for me it just means opening windows throughout the house for about 15-30 minutes per day. That alone makes a major difference on everything - Radon, PM 2.5, PM 1.0, CO2, etc.

Lastly just want to mention that it’s amazing to me how fast CO2 levels can rise with just my husband and I in our living room watching a movie. Good ventilation is something I definitely recommend everyone start measuring and working on.

[throw0101c]

> It sounds complicated but for me it just means opening windows throughout the house for about 15-30 minutes per day.

Not very useful when it is -10C (or colder) outside.

Current building science best practice can be summed up in the saying "Build tight and ventilate right.".

* https://www.energy.gov/indianenergy/articles/build-tight-ven...

* https://www.nrel.gov/docs/fy03osti/26458.pdf

Building tight prevents conditioned (heated in winter, cooled in summer) inside air from escaping, causing you to lose/waste money. It also prevents bad outside air (bugs, pollen, dust, car pollution, too humid/dry/cold/hot) from coming in.

Ventilating right means taking stale air from bathrooms (humidity) and kitchens (cooking VOCs) and exhausting it, and at the same time bringing in fresh air from outside on your terms: through filters and tempered to match inside conditions. This is usually done with HRV/ERVs.

Harder to do with older homes that need to be renovated, but now part of the building code for new builds in many areas (ASHRAE 62 defines ventilation volume/rate requirements).

[VoodooJuJu]

If it's -10C, then open the windows for 5 minute intervals, not 15-30, that's what I do.

[throw0101c]

So I've just paid money (and probably created a bunch of carbon emissions) to heat my home, and now I'm supposed to throw that money away?

[jnxx]

Not exactly. What you heat is the inside of your rooms, and a significant part of that heat can be felt as infrared radiation. When you ventilate in a quick and intensive manner, you exchange the air, which becomes cold for a few minutes but you do not cool down the room - because that takes longer. And the cold air has very little mass, so it is easy to re-heat again, and will be warmed by the walls etc.

[throw0101c]

> […] can be felt as infrared radiation.

Yes, I'm aware of mean radiant temperature:

* https://en.wikipedia.org/wiki/Mean_radiant_temperature

That doesn't deal with humidity (and other things like pollen in the warmer months).

[heliodor]

The energy stored in your walls is much higher than the energy stored in the air. Swapping out all the air for cold one will reduce the total energy stored in your house very little. The walls will reheat the air. Same with letting AC air escape for a minute or two.

[zsolt224]

Buy a co2 meter. You have to have windows opened for much more than 5 minutes. Aaaand you have to open them every 40 minutes, even when you sleep. Good luck with that.

[sn9]

Or you could stick a fan next to the window to increase air flow.

[dimitar]

For smaller homes switching from convection to infrared heating helps a lot, heating the surfaces instead of the air, means that letting the air mix by opening a window is less of a problem.

[drited]

Perhaps it would be useful to hear your experience with CO2 assuming you have already implemented these measures in your home?

[ambicapter]

There's a ventilation technique that uses heat exchangers to warm the air coming into your house and vice versa (can't think of the correct name for it right now). Something to look into to have the best of both worlds.

[throw0101c]

* HRV: heat recovery ventilator (temperature only)

* ERV: energy† recover ventilator (temp+humidity)

† Actually "enthalpy", but few understand that concept, so for marketing reasons "energy" is used.

[amluto]

It might help if “enthalpy” as used by HVAC people was closer to what “enthalpy” means in thermodynamics. The closest I can come is that HVAC enthalpy is the enthalpy of the air plus the enthalpy of vaporization of the water vapor in the air.

This is an oddly named but somewhat useful concept for air conditioning because water that condenses onto an A/C coil delivers its enthalpy of vaporization to the air conditioning system. So you can add “latent heat” to “sensible heat” and get a sensible answer.

But this is all a bit silly in the winter. In the winter, the primary consideration is not the energy cost of vaporizing the water in the air. It’s the amount of water in the air, how to get it there, how to keep it there, and how much humidity is safe for the building envelope. I doubt anyone measures humidity in units of BTU/cubic foot.

[hgomersall]

Mechanical ventilation with heat-recovery - MVHR.

[jaclaz]

>It sounds complicated but for me it just means opening windows throughout the house for about 15-30 minutes per day.

In practice what our mothers and grandmothers did, without having ever sampled air.

Some old reference:

https://news.ycombinator.com/item?id=25332981

[hnbad]

I believe the media has recently (ca 2020) taken to call it "German Lüfting" as it was temporarily celebrated as a solution to the ongoing pandemic.

[ben_w]

My local contacts in Berlin have called it Lüftschlag — air punch.

(Although, who knows, that might just be a weird localism, just like “Guten Nacht, schlaf gut, träum süß von sauren Gurken.” which I was taught in Köln and nobody else I’ve talked to anywhere in Germany recognises, though when I say I learned it in Köln they all go “Oh, Köln, yeah, they’re all crazy like that”.)

[hnbad]

As a Kölner by birth that localism does ring a faint bell though I wouldn't have said it's a Cologne thing if you had pushed me on it. We do have plenty of localisms due to the historical proximity to France though, and it always amuses me that "Plümo" (duvet) for example is completely unheard of in most of the German-speaking world and is usually replaced with the far less graceful and to me frankly confusing "Oberbett".

But the general term, as a verb, is "Lüften" or specifically "Stoßlüften" for the shorter form that is often mandatory for apartments with modern insulation but lacking a proper vent system to prevent mold.

On a sidenote: an interesting folk etymology exists for the Rhineland word "Fisimatenten", meaning something like "shenanigans", deriving it from French "visite ma tente", literally "visit my tent": the claim is that mothers would advise their daughters to avoid "Fisimatenten" because French soldiers during the Napolean occupation might invite them (in French) into their tents for, well, shenanigans.

[jnxx]

> But the general term, as a verb, is "Lüften" or specifically "Stoßlüften" for the shorter form that is often mandatory for apartments with modern insulation but lacking a proper vent system to prevent mold.

Exactly that.

To add, problems with mold are often due to insufficient insulation in some patches of the wall (like near windows), combined with humid air and insufficient ventilation. A properly insulated house should not form mold. But it is necessary to get humidity out, that's correct.

[funcDropShadow]

"Plümo" is definitely used in other cities on the west side of the Rhein. At least in Koblenz and Mainz.

[nicbou]

I've usually heard Stoßlüften (shock ventilation), and it's often part of the lease in Germany. It helps avoid condensation and mold.

[splitbrain]

Berlin native here. My mother (also Berlin-born) said "Träum süß von sauren Gurken". So not a cologne-only thing.

[thiht]

> In practice what our mothers and grandmothers did

Wait, people don't ventilate their home anymore?

[jaclaz]

Seemingly many people don't usually, I think it depends on the country/tradition/habits, in the thread I linked to:

https://news.ycombinator.com/item?id=25332981

there are quite a few replies of people that reported how they were not familiar with the concept.

And I have to underline how the evolution of building practices (again that depends greatly on different countries/local uses) generally speaking tends to make houses more airtight than before, so that ventilating should be more needed nowadays (with the exception of mechanically ventilated houses).

[altairprime]

I wasn’t taught to in the 80s, because we had a drafty home and it wasn’t necessary to do so consciously.

[eastbound]

> it causes CO2 to increase because there isn’t anymore large holes to bring fresh air in

Obviously you need the double-entry exchanger: Air comes in at 5°C and is gradually heated at 18°C by the air exiting, which starts at 20° and is cooled down to 7°C. No external energy required, it’s a classic of neutral-passive buildings.

[ahaucnx]

Yes, it is indeed amazing how fast CO2 levels can increase. This is especially a problem in low-ventilated classrooms.

At AirGradient we measure a lot of classrooms and it is not uncommon to see CO2 levels rising to above 4500ppm just within 2 or 3 hours. We wrote a blog post some time ago highlighting this [1].

[1] https://www.airgradient.com/open-airgradient/blog/we-measure...

[bokohut]

Irony in the timing of your post as I too bought an air monitor filtering device a few weeks ago given my interest in measuring things I cannot see that may impact my families health. After several weeks of use and no ‘major’ concerns this past Saturday evening the air quality was hovering just below severe for many hours and the house felt 'stuffy' to me. I checked the devices readings and then asked each child and my SO independently how they felt after taking a deep breath and for generalization purposes they all stated 'stuffy' in a greatly shortened term. With a significant delta in temperature outside and in I too opened all the external doors and we had a slight wind that was then blowing through for about 5 minutes. Within seconds the air quality began to improve and after closing the house back up the air quality for the remainder of the weekend, and even now, has been optimal and everyone has felt much better. It is very interesting to measure something one can otherwise not see, such as one's air quality, and then take action to improve upon that thing which we never before quantified against how we felt which clearly has impacted our health in ways we may never know. Yet again, what you cannot see matters most!

[dilippkumar]

+1 for Airthings wave.

I learned a lot about the ventilation situation at my place by tracking CO2 buildup. I now know that the time I should leave a window open to get CO2 levels indoors to approximate equalize to outdoor levels is 10x longer than what my intuition suggested.

I also discovered that every time I felt the air was “stuffy” and I needed some fresh air, it actually corresponded to a spike in VOx levels. When mom was visiting over summer, we discovered she is also sensitive to VOx levels.

This is my first winter with airthings wave. I’m curious to see how humidity levels are impacted by trying to keep my house warm.

[germinalphrase]

Open fireplace rather than a wood stove, yes?

[OJFord]

Not GP, but I assume either is going to be noticeably worse than no fire at all, a closed log burner better than open. It's not going to stop me enjoying a fire though.

I think they're way under-appreciated, by my calculation they're almost at gas boiler prices in terms of £/kWh of effective heat (currently paying 6p/KWh of gas) - and perhaps particularly as someone living alone, 'spot heating' is great - so cosy by the fire in the evening, way hotter than I'd want to heat the whole house (room even) with gas. I just wish I had one in my bedroom (& perhaps bathroom) too, I wouldn't even need central heating (well, maybe I shouldn't be so confident before Jan...).

[kylerush]

Yep. We have been wanting to get a fireplace insert which would be a major improvement in air quality, managing temperature, and how fast we burn through wood. The estimates we got were $2k for the insert and $2k to install. Still looking into it, but given the cost it’s not something we can move in immediately.