JLPT N4 Reading

In my town, for several years there has been a 'green curtain' scheme. In summer, a net is hung outside the windows of homes and schools and climbing plants are grown on it. The plants cover the window, blocking sunlight and cooling the room. When I first heard of it I didn't expect much; I couldn't believe plants would grow enough to replace a curtain. But when I tried it, by the end of July the window was completely covered in green. The room was about two degrees cooler and I used the air conditioner less. That's not all. I could eat the bitter gourds I grew. It also gave me a reason to chat with neighbours — 'they've done well this year'. A small scheme, but I feel I gained more than I expected. Q: What is the main point of the passage? — Even a small scheme can give more than expected.