Keeping Cool With “Green Curtains”

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    How does one keep classrooms cool when school buildings are horribly insulated and energy prices are too high to use the air conditioning? Well, you could try covering your building with plants:

    An elementary school in Itabashi Ward, Tokyo, is taking part in an experiment to grow plants covering its outer walls as a way to beat the heat.

    Sixth-graders tend the plant bed during breaks from class, checking the progress of cucumbers and dishcloth gourds whose stems extend over a net stretching from the ground to the third floor.

    The students at Takashima No. 5 Elementary School have been keeping an eye on the garden plants since the school year started in April.

    Itabashi Ward is regarded as an “advanced” locality in a growing “green curtain” movement aimed at setting up nets outside school buildings, public facilities and homes to grow plants. The idea is to block the sun in the summer and keep rooms cool, holding down the use of air conditioners to save energy.

    The movement is proving its worth this summer, with Japan seeing a stretch of record-breaking heat.


    Green curtains are not only refreshing and cool because they block the sun but also because the water that collects on the leaves reduces the surrounding heat as it evaporates.

    Kenichi Narita, a professor of environmental engineering at Nippon Institute of Technology, studied the difference in room temperature caused by the presence or absence of green curtains in a Tokyo elementary school room last year.

    He found a temperature difference of 1 degree when the windows of the room were open but found a maximum disparity of 4 degrees when the windows were closed. He also learned that the difference in “reasonable temperatures” rose to a maximum of 6 degrees because the sun warmed the room’s floor and walls and prevented the heat from being discharged.

    Maybe this movement will catch on, and Tokyo will turn from a concrete jungle into a real one?

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