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.