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The article cites windows opening inward as a reason for inefficient ventilation, yet the answer is to… insulate less? > The key may be to have less insulation

The article cites windows opening inward as a reason for inefficient ventilation, yet the answer is to… insulate less? > The key may be to have less insulation, because the current system seems to be too airtight to accomodate for residents' differing preferences Why not change the windows to open outward/upward?

rad_gruchalski 3y ago
The point is: you open those windows to let the humidity out. Warm air holds more water than cold air. The warmer it gets inside, the more humidity. If you don’t open your windows, the humidity escapes through least isolated areas, very often window sills. Sills get naturally colder, at below 12 degrees celsius you get mold in the sills. So, open your windows to blow the humidity out of the apartment but don’t open for too long so the sills don’t cool down too much, especially not below 12 degrees celsius.
- rawgabbit 3y ago
  Is there a modern type of window or device that will prevent mold, without requiring periodically opening the window?
  - blacksmith_tb 3y ago
    Yes, the device is a Heat Recovery Ventilator[1]. As you increase the insulation and airtightness of the windows to conserve energy, you need to bring fresh air in steadily (and pump air out). The HRV handles that, and passes the incoming air through a heat exchanger with the outgoing air, which is useful whether you're trying to keep warm air inside (in the winter) or cool air inside (in the summer. 1: https://en.wikipedia.org/wiki/Heat_recovery_ventilation https://en.wikipedia.org/wiki/Heat_recovery_ventilation
    - rawgabbit 3y ago
      Thank you for the link.
lxgr 3y ago
> the answer is to… insulate less? Yeah, that's an absurd suggestion. Insulation against heat transfer and insulation against mass transfer are also two different things. Although in a trivial setup the latter inevitably leads to the former, that doesn't need to be the case: Counterflow heat exchangers are a thing. > Why not change the windows to open outward/upward? Opening outward is much harder to handle (as it requires something to pull the window back in to close it); upward would need a robust mechanism that prevents the window from violently smashing down due to gravity. Sliding windows have neither downside, but are much, much worse at noise and thermal insulation.

rad_gruchalski 3y ago

The point is: you open those windows to let the humidity out. Warm air holds more water than cold air. The warmer it gets inside, the more humidity. If you don’t open your windows, the humidity escapes through least isolated areas, very often window sills. Sills get naturally colder, at below 12 degrees celsius you get mold in the sills. So, open your windows to blow the humidity out of the apartment but don’t open for too long so the sills don’t cool down too much, especially not below 12 degrees celsius.

rawgabbit 3y ago
Is there a modern type of window or device that will prevent mold, without requiring periodically opening the window?
- blacksmith_tb 3y ago
  Yes, the device is a Heat Recovery Ventilator[1]. As you increase the insulation and airtightness of the windows to conserve energy, you need to bring fresh air in steadily (and pump air out). The HRV handles that, and passes the incoming air through a heat exchanger with the outgoing air, which is useful whether you're trying to keep warm air inside (in the winter) or cool air inside (in the summer. 1: https://en.wikipedia.org/wiki/Heat_recovery_ventilation https://en.wikipedia.org/wiki/Heat_recovery_ventilation
  - rawgabbit 3y ago
    Thank you for the link.

lxgr 3y ago

> the answer is to… insulate less? Yeah, that's an absurd suggestion. Insulation against heat transfer and insulation against mass transfer are also two different things. Although in a trivial setup the latter inevitably leads to the former, that doesn't need to be the case: Counterflow heat exchangers are a thing. > Why not change the windows to open outward/upward? Opening outward is much harder to handle (as it requires something to pull the window back in to close it); upward would need a robust mechanism that prevents the window from violently smashing down due to gravity. Sliding windows have neither downside, but are much, much worse at noise and thermal insulation.