4 ms·

The article assumes buildings are air sealed. Which... they typically are not, even without considering things like operable windows. Real world C02 levels wi

The article assumes buildings are air sealed. Which... they typically are not, even without considering things like operable windows. Real world C02 levels will be lower than calculated at that ventilation rate. As we chase down ever more efficiency gains with insulation and modern materials, you end up with buildings that are substantially more air-sealed. That said, I've long thought, even pre-COVID, that prescribed ventilation rates ARE too low for my preference. One of the problems though is you end up conflicting with energy requirements. You have to heat, cool, and sometimes humidify/dehumidify any outside air to match the inside conditions. If outside air makes up a significant fraction, the energy use can be enormous.

PeterisP 3y ago
> If outside air makes up a significant fraction, the energy use can be enormous. I don't work on HVAC, but don't even simple passive mechanical heat exchangers cut out most of the heat difference from ventilation of outside air?
- Enginerrrd 3y ago
  Yes! But outside of urban areas, like in my area for example, that level of sophistication is relatively uncommon.
quickthrowman 3y ago
> If outside air makes up a significant fraction, the energy use can be enormous. This is what ERVs are for, conditioning incoming air from outdoors with the exhaust air. Enthalpy wheels are the most effective. https://en.m.wikipedia.org/wiki/Energy_recovery_ventilation https://en.m.wikipedia.org/wiki/Energy_recovery_ventilation > The article assumes buildings are air sealed. Which... they typically are not New buildings typically have a sealed building envelope/vapor barrier (excluding doors, obviously) and the HVAC system is balanced to account for pressure differentials. Commercial buildings typically don’t have operable windows, either.
- Enginerrrd 3y ago
  This is a very urban centric view. Not everywhere is so modernized and sophisticated.
  - TeMPOraL 3y ago
    Per-capita, in most of the world approximately everywhere is urban - non-urban dwelling is a rounding error.

PeterisP 3y ago

> If outside air makes up a significant fraction, the energy use can be enormous. I don't work on HVAC, but don't even simple passive mechanical heat exchangers cut out most of the heat difference from ventilation of outside air?

Enginerrrd 3y ago
Yes! But outside of urban areas, like in my area for example, that level of sophistication is relatively uncommon.

quickthrowman 3y ago

> If outside air makes up a significant fraction, the energy use can be enormous. This is what ERVs are for, conditioning incoming air from outdoors with the exhaust air. Enthalpy wheels are the most effective. https://en.m.wikipedia.org/wiki/Energy_recovery_ventilation https://en.m.wikipedia.org/wiki/Energy_recovery_ventilation > The article assumes buildings are air sealed. Which... they typically are not New buildings typically have a sealed building envelope/vapor barrier (excluding doors, obviously) and the HVAC system is balanced to account for pressure differentials. Commercial buildings typically don’t have operable windows, either.

Enginerrrd 3y ago
This is a very urban centric view. Not everywhere is so modernized and sophisticated.
- TeMPOraL 3y ago
  Per-capita, in most of the world approximately everywhere is urban - non-urban dwelling is a rounding error.