What is a Green Curtain?

Japan
What is a Green Curtain? Green Curtains in the Kyocera Group Grow your own Green Curtain

A Green Curtain is natural shade over the outside of a building window created by growing climbing plants such as goya (gourd) or morning glory. Thanks to the Green Curtain's ability to block out the direct rays of the strong summer sun, they help to prevent the temperature from rising inside of rooms and on the surface of buildings, and cool down indoor temperature through the transpirational effect of water evaporation from the leaves. In turn, cooler room temperature allows for energy-use reductions in air conditioner units and thus overall reductions in CO2 emissions.

Without Green Curtains  
Image: Without Green Curtains Strong sunlight shining directly through windows raises the room temperature inside of buildings. Furthermore, similar temperature rise of the ground or exterior walls near a window will also contribute to the rise of room temperature, and that radiant heat gets transferred to the human body. As a result, people inside feel hotter than the actual room temperature.
   
With Green Curtains  
With Green Curtains The foliage of the Green Curtains blocks out direct sunlight and reduces the amount of heat radiating into a room. In addition, by extending the growth of Green Curtains to cover the ground and walls in the proximity of windows, Green Curtains further help to prevent the rise in surface temperature of buildings, and thus decrease room temperature and the heat level that people inside actually experience.

Moreover, Green Curtains mitigate temperature rises through the transpiration effect. The transpiration effect works by drawing in heat when water absorbed by a plant is evaporated from its leaves. People inside buildings feel cooler due to the decrease in radiant heat penetrating into a room. Therefore, the transpirational effect of Green curtains helps create a cooler atmosphere than use of traditional window blinds.
   
Images provided by the Kyoto Center for Climate Actions

Preventing Rise in Temperature
Kyocera confirmed that use of Green Curtains is effective in preventing the rise in temperature of outer walls. By performing an infrared thermographic measurement of the outer wall area shielded behind the Green Curtains, and comparing it to the non-shielded areas nearby, the temperature of the wall shaded by the Green Curtain is lower than the non-shaded surrounding area. In addition, we were able to confirm that the Green Curtains can decrease the temperature by as much as 15 degrees C (27 degrees F), as shown in the graph of surface temperature between A-B-C and D-E-F.

Kyocera Sendai Plant in Kagoshima Prefecture, Japan
Date of measurement: August 3, 2009, 9:20am
Weather: Sunny
Air temperature: 32.2 degree C (89.9 degree F)
Measurement device: Infrared thermograph

The results obtained by infrared thermography , (Left): Visible image , (Right): Heat distribution image
Visible image Heat distribution image

Temperature difference between A-B-C and D-E-F are up to 15 degrees.
Measurement results obtained by infrared thermography

Absorption of CO2
Green Curtains reduce CO2 emissions as they help to prevent the rise in room temperature, and decrease the need to operate air-conditioners. On top of that, they actually act to absorb CO2.
1m2 of foliage absorbs 3.5kg/year of CO2*1. If you grow 4m2 of Green curtain, it will absorb the same yearly volume of CO2 as a cedar tree (14kg/year of CO2)*2

  *1 Source: Rural Culture Association Japan
  *2 One cedar tree absorbs 14kg/year of CO2. (Source: Forestry Agency of Japan)
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