Somebody, Open Up a Window!

April 1, 2011 — Spring is in the air, and you may find yourself ready to fling open your windows to let in the breeze. Follow that instinct! Natural air flow not only leaves you refreshed, but also ventilates a room without using energy.

How to Create Refreshing Air Flow

If you’ve got operable windows, you’ve got natural ventilation. You control the amount of fresh air entering a room by deciding how long and how much to keep your windows open, but also by the kinds of windows you have.

Types of Windows:

  • Casement windows, which swing out perpendicularly to the supporting wall, bring in the most fresh air because they open the entire window area to direct breezes indoors.
  • Windows that slide up and down are the most common type in the United States. These windows – which can be single- or double-hung – don’t open as much as casements but create great air flow when facing oncoming breezes. 
  • Operable skylights and clerestory windows take advantage of stratified air flow, which occurs when cooler air entering from below escapes out a higher window. This effect is most pronounced with taller windows and higher ceilings.

No matter what type of windows you have, you can increase air circulation by opening more than one. If you open two windows on different sides of a room, air flows across the room from one window and out through the other – an effect known as cross-ventilation.

If you’d like fresh air – but it’s one of those cold spring days – just open your windows wide for a few minutes. It’s better than leaving windows slightly opened all day, which cools the floors and walls, and leaves a lingering chill long after you close the windows.

Wait! Did you turn off the A/C or Heat?

Have you ever decided to bring in fresh air, and forgot that the HVAC system in your building, apartment or room was still running? Times like those can waste a lot of energy as the heating or cooling element in your living space overworks itself by trying to heat or cool the incoming air. So remember: Turn off the A/C or heat before opening a window for any extended period.

In urban areas, opening a window may let in pollution and allergens, which can aggravate those with seasonal allergies or who are sensitive to air particulates.  Still can’t resist opening that window on balmy days? Just research local allergen forecasts and air quality levels first.

And at the End of the Day…

Unless you intend to keep circulating fresh air in your living space overnight, make sure to close windows when you go to bed so you don’t cool down your space too much as temperatures drop for the night.  

By Efficient Windows Collaborative intern Julia Sendor