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Comment by willsmith72 | Hacker News Reader

How does an airtight house work day-to-day? If I don't open a window, how quickly am I poisoning myself?

Not knocking the idea, I've heard of them before and experienced the joy of triple pane glass (both in insulation and noise protection)

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They have heat recovery ventilation systems which bring in fresh air and send out stale air, capturing the heat in the process. But yeah, I am not sure what happens to air quality if the power goes out - I suppose you have to crack a window.

They still have windows that you can open

But yeah, I am not sure what happens to air quality if the power goes out - I suppose you have to crack a window.

So much for being "passive" then...

"Passive House" is a well defined term. It's a house that gets almost all of its heating from "passive" sources like insolation, or the appliances that run in the house.

I'm going to err on the side of caution and say that they were making a joke, as if the task of "occasionally opening a window" was enough to invalidate the entire concept of passivity from a passive house.

I was more referring to the fact that a "passive" house seems to actively require power to remain inhabitable.

I've had problems with some apartments where I had to have at least one window open 24/7 to keep the CO2 under 800ppm which is double the outside value. I feel a little unfocused at that level (standards say that starts at 1000ppm, I think I may be a little worse off with a broken nose).

Levels of CO2 which have detectable effects are easy to attain in a well sealed home. Levels which will result in a medical emergency (tens of thousands of ppm) are very hard to reach unless your house is sealed like a submarine.

I connected the dots at an office from a few years back about why I couldn't get anything done after lunch. CO2 levels were near outside numbers first thing in the morning and >1500ppm in the afternoon because HVAC was poorly done.

I suspect they set the recirculation as high as they legally can, to reduce HVAC costs.

The article mentions "Heat recovery ventilation", which means things like air exchangers [0] which pre-heat or pre-cool incoming air.

It is an active ventilation though, so you better run it periodically, even if you do not need heating/cooling. Your thermostat will have special setting for that, don't turn it off.

[0] https://www.productcleaningsolutions.com/blog/what-is-an-air...

Going off Wikipedia: When outside temperature is good natural ventilation is used, otherwise a heat recovery ventilation system is used to replace all inside air every ~2 hours. So to answer your question: you don't need to open windows for ventilation.

Moderately well sealed houses still exchange quite a lot of air, but if it wouldn't be satisfactory, they often have a fresh air vent usually with a heat exchanger to maintain heating and cooling efficiency. The HRVs and ERVs mentioned in the article are these kinds of devices.

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