Sealed surfaces and the problem with heat in Tokyo

Without further investigation

When we are looking at Tokyo, it’s green.
It could be greener, but it is also not pure gray.

However, as I heard, over the last decades it became warmer and warmer within the streets of Tokyo.

Especially gardeners like myself, but also people who love nature and are making day trips to the forests, know why..

The main reason might be:
We have too many people for too little space. Properties are expensive.
Where once stood one house with a garden for vegetables, two or three new houses are built.
Of course, one of the reasons is money. These big properties often belonged to elderly people. Their children are selling most of the land to finance their own house and the senior citizen’s home.
It is expensive to become old!

A lot of concrete….

Of course, there are rules when new houses are built to prevent the complete sealing of surfaces, but they are not as strict as in my hometown in Germany.
In Tokyo, most of the land can be covered by the new house. The land, which must remain (40%), is often turned into an exterior with a place for the trash box and a place to park the car and bicycles. These are often covered with concrete.
The free space around the house, 60 cm, is normally covered with gravel.

The people don’t want to spend their precious free time or money on work in a garden.
During the week, they leave early and come back home late.
On the weekends (if they even have two days off), they are sleeping and spending their time with hobbies or family, mostly somewhere in the city; playing golf, visiting an aquarium, a zoo, a play park, going to the cinemas. Or they are watching TV. They record their favorite series and watch them in their free time.
However, the property is not seen as a place to be on the days off of work. If they are staying home, it will be inside the house.
So people here tend to spend their energy and money into building a nice house. -Not a garden.

This little bit of green is already enough!

One reason why they don’t see a garden as a relaxing space at home is the mosquitoes. They are present from Late May / June until Mid / End October.
The time to enjoy the garden while it isn’t too cold is only from Mid April until the mosquitoes appear and from after they died until it becomes too cold, let’s say late November.
Another reason is, that it is too hot to be outside during summer.

And here we reached the core point: Why is it too warm in Tokyo in summer?

Because all the free surfaces are sealed to prevent weeds from growing and because every bit of space is used for living, shops or companies.

When I visited a very old house in one of the suburbs of Tokyo with my husband, we had an interesting conversation. My husband is Japanese by the way.
We visited at the beginning of July.
On the way from the station to the house, there was no green. Only streets, houses, and the outdoor parts of air conditioners.
He told me that it is so hot! It was true…
I told him, that the house has a garden and within the green, it will become cooler. He didn’t respond.
On the property of the old house are growing nice large trees, high bamboo, and a lot of shrubs.
We were occupied with escaping all the mosquito and couldn’t enjoy the garden to its fullest.
However, when we left, my husband told me, that it was indeed much cooler there and it is fascinating how the climate changes within two meters.

Said old house.

Yes, indeed it is fascinating how trees and a little bit of green can make such a difference!

Now we are facing the balancing problem.. How to tell the people in Japan to grow trees they don’t want to care for, only for the benefit of cooler streets? I mean.. Inside their homes, there are air conditioners, right?

This might be a little bit too much for most people ^_-

But.. Trees are not only for cooling the streets! If you plant trees and subs around your house, you can actively cool down your house too and don’t need to spend a great amount of money for the air conditioner bill.

There are more benefits, which outweigh the negatives.
Let’s see the negatives:

>>You have to care for the plants. Watering them in summer and pruning them around twice a year.

Solution: You can install an automated water supply and choose low maintenance plants.

 >>Installation and maintenance cost a lot of money. It is more expensive than concrete and gravel.

Solution: Start with weed barrier fabric and do the planting step by step by yourself when you have the money!
Gardens are seen as DIY projects in my home country and everyone is considered able to plant a low tree by himself.
The pruning of low maintenance plants can be done within one day.
In a year it shouldn’t be too much to spend two days in the garden.
It is a great benefit for the body!
Physical exercise refreshes and might result in the production of endorphins, which makes happy, and there are scientific studies, that there are antidepressant microbes in the soil, which makes happy. >>Read more at BBC

>>In a garden are lots of insects, which will come into the house. Especially cockroaches and ants.


Cockroaches are everywhere in Japan. We can not avoid them. However, if they find natural food outside, they are only coming inside the house by accident. If there is no food outside, they will try to find something inside..
It will be the same with ants and other insects.
If you are planting some flowering plants, you can help the environment a lot!
The world faces a great problem with bees dying all over the world.
However, bees are very important for our normal lifestyle. >>Read more at BBC
A lot of people are afraid to get a sting when encountering bees in the garden. But bees normally aren’t very agressive. Just don’t corner them and don’t try to hit them.
Let them in the flowers and they won’t hurt you.

Now let us sum up the benefits of planting trees and other plants around your house:

  • You are cooling down your house.
  • You are cooling down the streets (don’t be selfish, also think of others!)
  • You are helping bees and therefore the population of the whole world.
  • With working in the garden, you strengthen your body and soul.
  • You fight against global warming by providing CO2 binding trees.
  • You create a better climate because trees are creating O2 and special plants like moss can bind pollutants.
  • When having a nice exterior/garden, you won’t need curtains in front of the window anymore during the daytime. Trees can help you keep your privacy!
  • You make your house more attractive – let’s be true: some green is nicer for the eye than concrete only.

What do you think about a garden / some trees around your house? Do you have some? Or do you prefer concrete? If so, why?

Let me know what you think!

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2 thoughts on “Sealed surfaces and the problem with heat in Tokyo

    1. Hi Martin 🙂
      The garden is very beautiful and an interesting design.
      However, the problem here in Tokyo is not especially the rain, but the heat, which is reflected by the asphalt, concrete and stones.
      Actually, having places where the water can stand, like a basin (the houses here are designed that there is no rain water remaining on the grounds), is a great problem with the mosquitoes.
      However, the -how to call it- grass paving? We also have these in Germany, might be interesting for people here, searching for a solution for their parking spaces.

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