I don't have fans for ventilation at the moment and may choose not to have but I have big windows in bathroom. What type of window should i install? The common ones here are those rectangular ones that open from the top, with hinges at the bottom. The window swings open to inside.


The best types of windows for airflow are double hung windows ─ ones that open from the top and bottom. The top part lets out hot air and the bottom part allows fresh, outside air to flow indoors. This works especially well if the top window is near the ceiling, say, within a foot. Windows that open only at the bottom don't really allow a lot of airflow, since they don't allow any air exchange.


If having windows that allow for good ventilation is important to you, then you should invest in one of the following window styles:
•Single/Double Hung
•Awning or Hopper
from http://schmidtroofing.com/best-windows-natural-light-ventilation/

With a double hung window you can open the bottom and top of the window at the same time. This allows cool air to enter the bottom and hot air to escape out of the top. It makes it possible to ventilate a room using just a single window and to do it effectively. When trying to ventilate a room with single hung windows you need multiple windows in order to create airflow, and they still aren’t as effective as double hung windows at getting rid of warm air.
from https://modernize.com/windows/types/double-hung-windows

  • But only if they have full-length insect screens. Far too many have insect screens only on the bottom, which makes the window much less useful. – Ecnerwal Nov 4 '17 at 18:49
  • Your answer is simply not true. It can be demonstrated that a sideways crank window can allow more air in and out of a room because the full surface area is open and unobstructed (minus the screen), if the wind blows steady in a specific direction, that window would funnel air into the room (whether or not the moist air is displaced out the window is uncertain). In a double hung or slider, a portion of the opening is always covered, reducing area reduces how much air can be exchanged – noybman Nov 4 '17 at 20:19
  • Maybe crank windows have improved, but I have never liked them. A strong breeze can blow one open (actually happened to me) and destroy the window. And I believe the closed portion of a double hung window separates the incoming and outgoing airflows, though that may not make that big a difference. – BillDOe Nov 5 '17 at 1:37
  • I like that you noted near the ceiling, that will certainly make a huge difference no matter what window choice is made. – noybman Nov 5 '17 at 1:40
  • I'm worried that once I do it I realize window isn't enough to vent and I'd need a exhaust fan, which requires sticking it on the window. Double or single hung will prevent me from doing that in future. Awning or hopper windows at bottom with a fixed window at top might allow this however. But from my experience hopper window that was on same wall as shower didn't do anything at all to get air in or out. Never tried crank. – Altoban Nov 5 '17 at 15:55

I'm going to post this as an answer, even though I feel your question is one that cannot have an answer.

A: One that opens

Everything else is subjective. Your environment (wall opening facing N S W E? Location on planet, mountains, valleys, near external water?) plays a big part in this. If you live in a 4 seasons climate, using "just a window" is foolish. Even if it isn't a 4 seasons climate, a cold night, or a hot muggy day, and having max airflow is a BAD THING.

Generally speaking, opening a window of any "normal" size, in a bathroom with a shower for example, is more than sufficient for almost any bathroom unless its a steam room. Of course, the window has to be NEAR the water sources, within reason.

  • The window faces the shower but on opposite side. Does steam or hot air get stuck on the ceiling and not distribute around the room? – Altoban Nov 5 '17 at 15:40
  • the hot air rises is all. As long as air is able to be exchanged and the window is open, its going to be better than no window at all. I just don't think you are going to find a one-size-fits-all perfect window for air exchange. The opening of a window (even a few inches), is going to allow moist air to escape. Unless you have winter climate, then you really wouldnt want to open a window. – noybman Nov 5 '17 at 15:53
  • Before coming here I was leaning on getting awning windows, in case I wanted exhaust fan in future, but I wondered how will hot air fnd its way to the open gap so that's why I was concerned about airflow. – Altoban Nov 5 '17 at 16:01
  • The fan route will ensure air can be effectively forced out (provided the whole house isn't so tight it cannot breath, and most houses aren't). The window will allow hotter air to escape. The water vapor will cool and the walls will become wet, the fresh air with (presumably lower humidity) will promote drying. This is going to happen as long as a window is open. The type of window is mostly a preference/style thing. The bigger the opening, the more air that can be exchanged. – noybman Nov 5 '17 at 16:11

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