Apparently there was a fad for building schools with no windows. There's a 70s era middle school in the (U.S.) town where I live; it won a design award for its total lack of fenestration. It was supposed to reduce distraction or something.

My schools were all like that. "Kids aren't paying attention to our standardized-test preparation studies! Perhaps we should make schools more like bleak prisons, and force people to spend the bulk of their formative years there! That will certainly result in a more capable general populace."

My HS in central NJ had neither windows in the classrooms, nor WALLS. It was designed like a giant open office bullpen thing and classes were supposed to congregate in vaguely defined areas. By the time I got there in the early 90s, they had already erected borders everywhere out of movable chalkboards, so you basically got a traditional classroom layout but with noise pollution from all the other classes going on nearby. Great job all around. (Though I suppose from the CO2 standpoint we were probably doing better than most!)

The walls were part of a new teaching fad. I lived in a city that tried it out in one school. Each floor was an open plan for the classrooms. This one elementary school was their trial.

The teachers had a love/hate relationship with this plan.

Sounds like HHS. I was there in the 00s and the borders were these "permanent" accordion wall things

In many countries forcing people to stay in a room with no windows would be illegal, and for good reason.

My school was like that. I always heard it was in response to the 1970's energy crisis - windows are bad insulators.

I ran a CO2 monitor in my classroom and found it exceeded 2000ppm on some occasions. Typically it would be 1200-1600. I discussed this with architects when building a new facility, and the new facility tests at <900ppm fully occupied.

I think the high levels before led to worse behavior and lower academic performance. Both seem generally better now.

Same. I run a CO2 monitor in my classroom too. It gets up to 2000ppm very fast without the fan on.

My senior year, the high school installed blowers in each classroom. We were told it was required by a new California law.

I’m not sure it was an improvement: the blowers were noisy and made the classrooms much less comfortable (colder in winter, warmer in summer; it was an older school and the HVAC systems weren’t great). Teachers constantly talked about how they wanted to destroy the blowers. I seriously doubt grades improved. I wonder how previous students managed before our enlightened times.

Buildings used to be much draughtier, so it wasn't so much an issue.

My landlord at my old place was always adding new insulation. Co2 levels there would get really high with windows shut. My new apartment has much lower ambient co2. Both were built 100 years ago.

I think people also used to leave windows open a bit, even in winter. My (Canadian) grandma always did, and I hear it was the custom in Germany.

Modern buildings are made to be hermetically sealed.

Definitely true. You can measure how leaky a building is by sealing it up, blowing air in the door, and measuring how the pressure changes. If it’s very leaky the pressure doesn’t rise as much.

https://en.wikipedia.org/wiki/Blower_door

We used to assume that you’d get enough fresh air from infiltration through accidental sources. With a better sealed building, that’s not always the case and you may need to deliberately bring in outside air. Heat recovery ventilation systems help to do this more efficiently than the inadvertent leaking method.

https://en.wikipedia.org/wiki/Heat_recovery_ventilation

HRVs also let you control where the fresh air comes in and where the stale air leaves. This means you can do clever things like bringing fresh air into bedrooms and removing air from bathrooms.

Thanks. I really hope hrv systems become standard. My brother has one in his house and it seems to help keep down co2.

Do heat pumps ventilate? I have one in my new apartment and co2 seemed higher when it was off. But I was told they are not hrv systems. Maybe the blowing fan just caused more air circulation.

Home heat pumps generally do not have an outside air connection. They assume that your house is drafty enough already.

At least here in BC, I believe it is code to include a fresh air vent with any central HVAC. Our house has one (built in 1992). Of course, if the house is tightly sealed and you don't have an exhaust fan running, it won't suck in much outside air.

Since the climate is moderate where we live, what's been suggested to me is to just run the recirculate fan often/always, and to use bathroom exhaust fans to control fresh air turnover. (As built our bathroom fans are hooked up to a central humidity sensor, and will turn on when house humidity reaches a set level (as well as being able to turn them on in the bathrooms). I'm actually curious whether something exists, or I could rig something up, to turn them on based on CO2 levels as well.

> I hear it was the custom in Germany.

At least when I went to school it was almost impossible to keep a window open except on the hottest days of summers because inevitably n>1 [almost always] girls would start to complain about draft. (edit: is draft in a room with only one opening to the outside a social construct?)

That being said I always keep the window open in my office. There is no draft.

When I was in elementary school, one of my classmates ended up missing school for a while because of a bad heater and carbon monoxide poisoning. That freaked me out. But everything I read was that this was a relatively new problem because newer houses were less drafty than old houses. It wasn’t clear to me (at the time) whether old houses were draftier when built, although I have to assume they were (otherwise carbon monoxide poisoning would have been just as common when those houses were new).

I even remember wearing sweaters indoors when I was young. I assumed that was an effort to save money during the so-called Energy Crisis (better described as a shortage of cheap oil), but it may have just been the natural reaction to inefficient heaters and the building standards at the time.

Yes, building standards have changed dramatically in the last 50 years. In particular, plastic "house wrap" vapor barriers are standard now, which is a product that had be precedent. There is a tremendous amount of air exchange even through a well-built 'solid' wall with no vapor barrier.

A vapour barrier is different to an air barrier... An airtight membrane is not necessarily vapour tight.

Maybe this is a tradeoff people need to consider when trying to reduce their wasted energy in buildings. Maybe try to do some kind of heat exchange in the air exchange?

I know of at least one case where a family was killed because they were using a laser cutter on wood indoors in a well sealed building and the small levels of CO released were able to build up to lethal levels.