A few months ago, you probably were desperately trying to stay warm in your abode during the Japanese winter. Then, after a brief, gentle spring, usually as soon as Golden Week is over, the aircons start whirring everywhere in a desperate and energy-consuming attempt to cool down the nation during its hot and humid summer. Japanese houses, unfortunately, have poor or non-existent insulation and can get extremely hot and stuffy during this time.

If you want to reduce your electricity bill or are living in a home that doesn’t have an air conditioner, here are eight quick fixes and two long-term changes you can make to keep your home cool during the summer months.

Quick fixes

1. Keep your curtains closed

Prevent your home from becoming a greenhouse and close your curtains or blinds during the day, at least in rooms like the bedroom that you aren’t currently using — and especially on the south side of your home.

Up to 30% of unwanted heat comes from windows, and this simple trick can reduce indoor temperatures and your bills quite a bit.

Even better, get blackout curtains to insulate your room. Make sure to pick them in a light color with a white plastic backing to reflect the sunlight.

2. And close the doors

Needless to say, keep your veranda and front door closed during the heat of the day. But also close off all unused spaces physically by shutting your doors in the home. This stops the precious aircon or natural breeze from dissipating into spaces that don’t need cooling.

3. Switch on the ventilation

If you are taking a hot shower or are cooking, make sure that the fans in your bathroom and kitchen are on. Heat rises and the ventilation system will absorb and suck the heat out of the house.

4. But close your vents

However, it may be a good idea to close the vents during the heat of the day. Most Japanese houses have vents in the main rooms like living and bedroom. Close them off to stop hot air from seeping in. The vents can also be a way for insects to enter your house during the humid summer months, so keeping them closed might be in your best interest.

If you live in an older building that has a lot of cracks, it might be worth it to have them filled to stop the constant loss of cool air in summer and warmth in the winter.

5. Take advantage of the night air

During nights that are cool enough (after an 30 °C+ day, 25 °C will feel pretty good), open up your windows! Make sure to keep the fly screens closed though, as mosquitoes flourish in the humid summer in Tokyo.

You can also try to create a cross breeze by opening windows on opposite ends of your home and placing a fan in front of a large window or veranda door to fan in the breeze. Just make sure to close them again before the heat returns from the early morning hours onwards.

6. Change your light bulbs

Incandescent (probably known to many as simply “normal”) light bulbs release quite a lot of their energy as heat, not as light, which is warming up your place. So summertime might just be the motivation you needed to switch over to LED or compact fluorescent lamps (CFL). This will lower your electricity bill and can make a difference especially in smaller rooms.

7. Don’t bake, barbeque

Using your stove will heat up your kitchen, and using your oven even more so. You might want to give roasts a miss during the hotter months and instead opt for a BBQ outside — after all, this is the reason why we associate barbeques with the summer. For those that don’t have a garden at their disposal in the metropolis, there are a few spots in Tokyo that allow public BBQs or have facilities to rent.

8. Water hacks

If you are seriously overheating and your air conditioning is broken or non-existent, it might be time for some hacks involving cold water: Place a bowl with ice cubes in front of your fan, best angled forwards, which lets the breeze catch on to more surface of the ice. The resulting flow of cold air almost feels like air conditioning!

Hanging a wet bed sheet in front of the window during the evening hours also cools down the air blowing inside significantly.

Finally, consider misting your bed sheets with water until they are slightly damp to get a good night’s sleep if modern electronics have failed you.

Long-term changes

If you own a detached house, here are two more ideas to keep your abode cool:

9. Plant a tree

If you have your own home and a garden, think about planting some shading vegetation. A large tree strategically placed to shade windows on the south side of your house, or any large window that absorbs a lot of sunlight during the day can really help cooling your house down in summer. Choose a deciduous tree, so that the bare branches let the sun through in winter.

Also, think about adding vines to your house. They significantly cool down a building. Many people are weary of them, claiming that they destroy buildings and are unstoppable. But it all depends on the species you select. Talk to a landscape architect to find out which one would work for you.

10. Paint your roof

A flat roof in the midday sun receives about 1,000 watts of sunlight per square metre. Painting your roof white reflects about 85% of the sunlight and can decrease solar heating (the professional term for your house being warmed up by the sun) dramatically and could reduce your cooling costs by more than 20%. This works best for detached houses with one or two floors.

By Mareike Dornhege

Similar to this:

Why Japanese buildings are so cold in winter

The man with the most energy-efficient house in Japan

Passive houses: What they are and why they're gaining popularity