CO2 and VOCs, but what about PM2.5 and PM10? What about pollen? What about humidity control?
Cracking a window is also costly, since it directly raises your heating and cooling bills. It's just an "invisible" cost that's easy for some people to ignore since it's hard to directly measure. An ERV pays for itself over time, so it's more a question of whether you can afford to just crack a window?
Living in an apartment makes this difficult because your landlord may not let you improve this situation, but just ignoring the cost of opening a window doesn't make the cost go away.
I live in the DC area and whenever I hear people say "just crack a window" I think, that brings in all of the pollen I'm allergic to in all seasons except winter, plus humidity and 95 f degree heat if it's the summer... I' be been looking into getting an ERV for a while.
The humidity and temperature are rough. Some months I can't open the window at all. This month has been pretty good though, huh? At least for the temperature and humidity.
I feel you about the pollen. I use a Blueair filter, and that keeps PM 2.5 and PM 10 in check.
Don't leave your windows open all the time. Open them for 5-10 minutes at least once a day. Heating air is cheap, it's heating all the other mass in your home that's hard, so don't let it cool down.
If you live somewhere uninhabitable like Texas, change heating for cooling.
The GP comment is technically correct, if somewhat incomplete. A 40 m3 room (about 14’x14’x8’) has about 50kg of air in it; that’s only ~300 Wh to heat every molecule of it by an entire 20C. The thermal mass of the other things is orders of magnitude larger.
The reason that I consider that explanation somewhat incomplete is the behavior of the air and the embodied energy. Imagine it’s winter, the exterior air is quite dry, and you open a window. You will easily lose a large amount of moisture, making the air uncomfortably dry. So you turn on a humidifier, but that will cool the room further with the evaporation of water. You also have to consider convective heat transfer. The fast-moving air is quite good at transferring heat to the outdoors. So, even if you don’t care about humidity, you will lose a lot of heat through convection.
But yes, strictly speaking, the thermal mass of the air is very low in most structures and situations.
I've got one laptop case where it is quite spongy with panels like neoprene and some stretch fabric. When I ride about half an hour with a driver who is not smoking but had smoked in the vehicle (supposed to be always with the windows open out of courtesy to the other drivers), the next morning when I pick up the laptop it smells like tobacco and it takes a few days to go away. This doesn't happen with the backpack which is not built like that.
You can also take the domestic calculations further.
If you have 50 kilos of dead weight for instance, whether it's a set of workout weights or a piece of furniture, and it's all a stable 10 degrees C through and through, it's going to take 50 kilos of 30 C warm air constantly coming into intimate contact with the dead weight however long it takes before your dead weight gets to 20 C and the air does too.
That can be a whole lot longer without forced air. But it still takes 50 kilos of air no matter what.
>the thermal mass of the air is very low
This is exactly it, along with heat exchange capacity.
If you pull out the water hose you could spray it down with 50 kilos of water in no time, but not everybody's living room can withstand that :)
Now if you had 500 kilos of 20 C furniture along with everything else, and you opened your windows and let out the full 50 kilos of air which was fully replaced by 0 C air, then shut the window to achieve a closed system once again, you'd still be sitting on 20C furniture for some time and only breathing 0C air for a short period before the overwhelming mass of the furniture itself warmed the much lesser mass of air right back up a few degrees, and to about 18 C eventually. Which none of the other heated mass will drop below.
With no additional heat added, assuming insulation was perfect, but that's the number of degrees lost from one single full air exchange alone under those conditions.
While the windows are open is the time to vacuum the carpets, drapes and furniture so you can get some forced air through them and let absorbed irritants out instead of just stir it up and move it around. The high-surface-area porous materials can soak up more than you think.
Air exchange matters again because some of the irritants are not the kind that evaporate or "dissolve in air" very fast, and they might have had all kinds of continuous time to accumulate.
You've got to figure that curtains can hold grams of unwanted stuff in their pores from previous bad air days, furniture ounces & carpets pounds plus a lot of the latter is solids which may give off odors or stir up allergens for quite some time once it has gotten into the pores and other tortuous passages. That's a lot of air exchange when you do the math.
Change your air filter after stirring things up and breathe easier after that :)
Cracking a window is also costly, since it directly raises your heating and cooling bills. It's just an "invisible" cost that's easy for some people to ignore since it's hard to directly measure. An ERV pays for itself over time, so it's more a question of whether you can afford to just crack a window?
Living in an apartment makes this difficult because your landlord may not let you improve this situation, but just ignoring the cost of opening a window doesn't make the cost go away.