Why are Japanese homes so poorly insulated?

Apartment buildings in Tokyo Photo: Japan Today

The rising cost to heat homes this chilly winter raises the question of whether or not one's dwelling is well insulated against the elements. Masatoshi Takeuchi, an architect and professor at Tohoku University of Art and Design in Yamagata answers this question.

"Among the G7 countries, Japan is the only one not imposing insulation requirements on housing construction," he tells Weekly Playboy (Feb 13). "In Asia, even South Korea and China have insulation requirements."

"Many economically advanced nations , as part of their global warming measures, are constructing housing with outstanding energy-saving and carbon-free properties," Takeuchi continues. "But Japan is way behind. It is still stuck in the energy-saving policies adopted in 1999. Which are not even mandatory. And even the insulation that clear standards suffer in comparison to countries like Germany. For a dwelling in Japan having 100 square meters, the volume of kerosene required for heating over one year is seven times that of Germany. And the majority of existing homes in Japan don't even clear the country's own standards." 

In fact, points out Takeuchi, fewer than than 70% of Japanese homes conform to to the insulation standards that were applied from 1980.

Takeuchi identifies two main reasons for Japan's poor showing. "The first is the preconceived notion that Japan is a warm country... so standards have been established with this in mind. But Japan no longer has the temperate four-season climate it once did. Summers in particular are getting harsher every year, making air conditioning a necessity. In the past, a well-ventilated house was considered ideal, but nowadays you don't want to live in such a house, because at 40° C, any breeze you feel will just be hot wind.

"The climate is changing, but the standard of house construction has not changed," he said.

The second reason is attributed to misguided views relating to housing and the economy, driven by the widespread belief that the total number of housing starts is tied to economic performance, i.e., when the economy is strong, more houses are built, and vice-versa.

"Therefore, when talk of establishing a new construction standard comes up, some people are wont to object, saying, 'Won't that hurt the economy?'" Takeuchi said. "In fact, the cabinet once did approve of implementation of mandatory standards for insulation by 2020, but the Ministry of Land, Infrastructure, Transport and Tourism strongly opposed it, claiming it would affect small- and medium-sized home builders, who 'lack experience.' The ministry's view was that if the standard were implemented, the number of construction starts would decrease, hurting economic growth."

As things currently stand, compulsory insulation requirements won't go into effect until 2025. Nevertheless, builders are installing insulation proactively and Takeuchi estimates that about 85% of single-unit houses and 70% of apartments currently being built will meet the new standards.

When the mandatory insulation standards are finally adopted, owners of existing structures are likely to become eligible for home-improvement subsidies.

Raising the quality of insulation will require 10-cm-thick glasswool insulation panels for walls and 20cm-thick panels for ceilings. Another measure is installation of double-glazed windows, with aluminum exterior and uPVC inner sashes. (Sashes composed 100% uPVC afford even better insulation, but at higher cost.)

Affordable measures like insulation-type window blinds are also readily available.

"The blinds are like wearing a down jacket, which traps heat between the body and the jacket," Takeuchi tells Weekly Playboy, adding, "Condo residents may be able to improve insulation without extensive renovations by installing a new type of inner sash. Tenants might want to discuss the matter with their landlords and offer to share the costs for installation. Chances are they'll get a favorable response."

© Japan Today

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Correct me if I'm wrong, but Japanese houses are considered disposable, and that's why they lose value? The only winner in resisting insulation are greedy builders. Good builders, which there are plenty, insulate homes. For instance, my house, built in 2018 included sprayed expanding foam insulation and it's amazing how well the home holds temperature. Developers building cookie cutter homes for max profit? They are the issue. Even then, some are insulating.

21 ( +26 / -5 )

It is such a joke that up here in Northern Tohoku that we are stuck with housing with only a few centimeters of Styrofoam insulation. And then people wonder why their pipes keep freezing, and they all must huddle in one room for the majority of the winter! All because builders and the government are just too damn lazy to do anything to help out the average consumer.

16 ( +24 / -8 )

Back in the day, most Japanese were content with taking hot baths before bedtime and warming their feet under the kotatsu. I didn't have air conditioning or hot running water for my first 10 years in Japan. Bodies crammed together on commuter trains also had a warming effect. We managed.

-11 ( +8 / -19 )

"In fact, the cabinet once did approve of implementation of mandatory standards for insulation by 2020, but the Ministry of Land, Infrastructure, Transport and Tourism strongly opposed it, claiming it would affect small- and medium-sized home builders, who 'lack experience.'

Right here. Instead of keeping an incentive for one's innovation or improvements , natural to free market, let's kill it and keep those lacking experience in the business by protecting them.

Why would anyone want to improve and gain experience when there is also no pressure from consumers?

8 ( +15 / -7 )

When buying a house which then constructed on site, the buyer can request all the upgrades they want provided they can pay for it.

5 ( +11 / -6 )

An increase in building codes translates into increased buying prices. An article yesterday on the increase in costs of building accommodations in Tokyo.

2 ( +6 / -4 )

Basically, they started building temporary housing after the war and saw there was a money in the churn of sub-standard, disposable houses and just kept building them. The people didn't know any different and were told it's the way things are done in Japan.

8 ( +16 / -8 )

No only do well insulated home's keep you warm in the winter they keep you cool in the summer, therefore cutting heating and air-conditioning costs. In Canada new home construction is very comfortable.

16 ( +17 / -1 )

After 3 years of a total interior remodel of our 20 year old used home auction purchase, we have r-16 pink insulation (imported) between the walls on the 1st floor and 80mm of blue board on the 2nd floor. Moved in around September. A long fun project and we’re not done yet.

10cm’s of insulation in the panels is a great start. But yeah, as some have already said, if there’s no pressure from consumers and a brown bag government, nothing much will change. Higher energy costs might be the catalyst.

invalid CSRF

18 ( +20 / -2 )

New homes should also have solar panels and heat pump systems and central heating. There no accessible roof space and there is never any insulation there.

9 ( +12 / -3 )

The insulation in my condo is a joke.

I really should have sued but it’s too late now.

New windows and insulation are items #1&2 on the renewal list.

12 ( +12 / -0 )

We built our Japanese home using a company that specializes in keeping homes energy efficient. Basically we have solar panels and very good windows and insulation. Our monthly electric bill runs around Y5,000 a month and that is with keeping the home at 70 degrees throughout the house.

22 ( +22 / -0 )

Just read the Mainichi which said today, "Students are forbidden from wearing coats at some Japanese schools, even as a severe cold spell hits the archipelago." Could this be due to the reason stated in the article above about why home insulation is scarce in Japan. "Takeuchi identifies two main reasons for Japan's poor showing. The first is the preconceived notion that Japan is a warm country... so standards have been established with this in mind."

8 ( +9 / -1 )

For a dwelling in Japan having 100 square meters, the volume of kerosene required for heating over one year is seven times that of Germany. And the majority of existing homes in Japan don't even clear the country's own standards." 

This is laughably false. The average German house uses 160kWh per square meter for heating (see link). For 100 square meters, that would be 1600 litres of kero per winter. Seven times that would be over 10,000, meaning the average Japanese would be paying 10000x110 yen per litre, or 1.1 million yen to heat their house. This is clearly false. Germany does have some very high standard houses, such as Passivhaus standard, but they are a tiny percentage of the total.

I remember reading somewhere that average household use in Hokkaido is around 2000 litres. 2000 is not seven times 1600, and Hokkaido is far colder than Germany.

European houses have been warm in the past few decades due to central heating using huge amounts of cheap natural gas. Now gas is expensive, comparable to what we pay in Japan, people are rationing its usage and their houses will not be as warm as your memories of them may be. I'm sure Japanese houses would be warm if natural gas was 2-3 yen a unit.

-1 ( +7 / -8 )

EvanToday  09:00 am JST

Correct me if I'm wrong, but Japanese houses are considered disposable, and that's why they lose value? 

Japanese tax laws call for writing down the value of a house in 30 years. Hence in many cases the value of the land (land & house are not always together) often exceeds the value of the house. In addition, demolishing existing houses and building has been an economy driving tactic since WWII ended and the country focused on rebuilding.

In the US second hand homes are routinely bought and sold, and new residents just move right in. Whereas in Japan, when second hand homes are sold they are immediately renovated by the buyer, or already renovated by a developer.

Only in Hokkaido have I seen single family homes with central heating (panel heaters), thick insultation throughout, full PVC or Resin window sashes, double thickness windows, etc. I presume this will lead a change throughout Japan as the article suggests. There are still many older non-insulated homes with the only heating source being a room heater and kotatsu. This issue has been highlighted bythe medical industry as a high number of elderly suffer from BP surges as a result of freezing cold bathrooms.

9 ( +10 / -1 )


No only do well insulated home's keep you warm in the winter they keep you cool in the summer

Agree, since we insulated the walls of our house we have noticed the difference in how little heating we now use in comparison. Also during the heatwave we suffered last year the house was cooler than the air outside. We also have a white lining on all curtains so as to reflect the light back in summer which makes a surprising difference to the sun facing side.

I have never understood why modern Japanese houses only last a generation if that, nor the mindset that they have to have a “new” house. I was born in a house dating back to George the first and have lived in properties over the years ranging through the centuries since. Old or “second hand” houses are the norm here and oddly do not collapse after 30 years!

11 ( +11 / -0 )

If Japan wishes to conserve energy, decrease atmospheric pollution, and cut operating costs then insulating buildings is a good way to go . . . using less energy to heat a building during winter cold months and using less energy to cool a building during the summer hot months . . . .

10 ( +10 / -0 )

On one street near my place, 6 houses near each other started renovations around the same time at the beginning of the year. And 2 others houses on that street was torn down and rebuilt last year. Another house between two of the renovations is currently being torn down. I do not know what is going on that street. It is like every one won the lottery, some public health risk happened, or they know something major is going to happen, so they are preparing to cash in.

Back to the story:

Construction, industrial cleanup, and demolition is traditional ran by the Yakuza, gangster wannabes, bozoku, & etc. It is one of the few legal businesses that they use as a front, and it employees a lot of people who fall threw the educational cracks or have an immigration issue. That means lots of cheap unskilled labor doing work no one else wants.

They have multiple reasons to keep the cheap impermanent housing racket going!

In fact, a lot of the Japanese businesses are based on this idea of "impermanence," so everybody needs to pay again.

6 ( +9 / -3 )

Part of my home has been without insulation since Xmas due to 3 burst water pipes between the 1st and 2nd floor and in the walls. The water soaked the insulation. With the added weight, it fell through the ceiling of the 1st floor, talking down everything. It was a mess. The water company turned off water to the house at the street. It was gushing out, I hear. We weren't home.

The heating bill for last month was over US$100 higher because it was missing that insulation. This month's heating bill will probably be $100 more too. Insulation matters. Our home is fairly efficient thanks to added insulation. We typically pay 50% less than our neighbors for heating/cooling.

Hopefully, they'll rebuild everything this week or next. The vapor barrier, insulation, wood floors, and a few walls are all missing in that part of the house. Brrrrrrr.

8 ( +8 / -0 )

Because they lack the materials and core resources to build better homes. Building better homes requires more materials, so more costs. Japan is a heavily importing nation, so the general trading houses must cut costs by importing less viable materials to build houses.

With the ongoing weak Yen, lack of viable workers, and decline of national power, expect more tofu-dreg buildings in Japan for years to come.

-12 ( +8 / -20 )

For the folks downvoting me, just do the calculations. 160 kWh per square meter in Germany for heating. Japanese people do not use seven times that. They probably don't even use double. No one could afford to do that at Japan energy prices on a Japanese pension or salary.

It's not that Japanese houses are bad, of course they are, its that European houses are bad too. Europeans just hide their houses' shortcomings with natural gas from the North Sea or from Russia. This used to be very cheap, but is not any more. You can criticise Japanese all you like, but do not hold up Germans as a gold standard.

If you want a warm house in Japan, just build a new place with Ichijo Komuten, Japan's No. 1 builder, who put up about 12,000 houses a year. Their designs are bland, but the houses are well constructed, way better than anything you would get from a developer in the UK. Look at the C and Ua values.

-1 ( +3 / -4 )

Everytime I have to leave the one warm room in my in-law's house to use the freezing bathroom, I ask myself why Japan, one of the wealthiest and most technologically advanced (when they want to be) countries in the world for decades, cannot make a warm house. It's absolutely baffling that no one thought to use decent insulation or central heating. Newer housing seems a little better, but that's still endless thousands and thousands of dwellings that are absolutely substandard. Just an incredible situation that wouldn't be considered acceptable in any other wealthy country.

11 ( +11 / -0 )

"bathroom" In Japan "toilets" are separate from the "bathroom" and many have a heated toilet seat. I wear the right amount of clothing to help keep me warm.

1 ( +3 / -2 )

wallaceToday  10:00 am JST

"bathroom" In Japan "toilets" are separate from the "bathroom" and many have a heated toilet seat. I wear the right amount of clothing to help keep me warm.

Personally, I heat my houses. That way I don't need to go to sleep while wearing a hat while I'm on the main island.

1 ( +3 / -2 )

But you still need to wear trolls to keep warm. How do you heat your houses? Gas, kerosene, electric heaters, ac? Do you leave the heating on 24/7? Must be very expensive and wasteful.

-1 ( +2 / -3 )

1) Because Japanese prefer little spot solutions for symptoms rather than fixing the root cause. That little fan heater you quickly switch on when you return to your cold house gives you the feeling of control, and that your actions are leading to a better world.

2) Because comfort is only appreciated when there is discomfort. The glorious toilet seat is only warm because the house isn't. The Kotatsu is only cozy because your house isn't. That Hokkairo is only a blessing because of you chose the wrong clothes.

3) Because you should accept what you cannot change. You (most often) cannot choose your house or do something about it. Only very few actually build a house to their specifications. Landlords don't pay the energy bills, so they just want a cheap construction and most houses are glorified yurts.

4) Because it would take away the opportunity to be a great host by overheating the house to 30 degrees Celsius upon arrival of guests to show your hospitality. How would anyone know you are trying hard if there aren't heaters to switch to max (=guest) mode.

5) Because that's all most Japanese know, and you can't want something you don't know. If you've ever lived in a comfortable modern house overseas, you know that the quality of life in a Japanese home in many aspects is simply sub-par. But if you haven't, it all you expect.

-2 ( +14 / -16 )

Kotaro Iwano

excellent post!

bathroom" In Japan "toilets" are separate from the "bathroom" 

that's the best thing about Japanese homes for me. I personally believe you shouldn't poo or pee where you shower or bathe.

-11 ( +6 / -17 )

What is the history behind how paper walls became acceptable in Japanese homes?

4 ( +5 / -1 )

A calculation should be made as to how much energy and money could be saved, and how much CO2 not generated, if decent insulation was the rule, rather than the exception, in Japan.

7 ( +8 / -1 )

The best rationalization I ever heard is that Japanese houses need to breathe.

4 ( +4 / -0 )

Organic houses made from wood, mud, and paper need to breathe to reduce the levels of humidity and mold.

2 ( +2 / -0 )

My brother in-law says that houses are poorly insulated because they will go moldy otherwise. And no doubt he was told that years ago and won't change his mind, despite evidence to the contrary. Other countries have tackled these issues successfully.

9 ( +9 / -0 )

When we had our new house in Japan built a few years ago, having it properly insulated was the biggest priority for us, so we planned everything out to the smallest of details. Fully insulated both floors, the bathrooms, garage as well as heated floors in the kitchen, dining, hallways and restroom. Our old condo was decent, not the best but better than the older traditional built homes. I’m glad this article came out, this has always been a subject matter that a lot of people don’t talk about enough. When I first came to Japan, we stayed at friends old house that was built in the mid 90’s and I was shocked at how cold the place was at that time, you couldn’t even use the toilet without a jacket.

8 ( +9 / -1 )

On the issue of mold; there was an article in Scientific American about the secret of really, really old wooden structures. The article looked specifically at the very old wooden churches (stavkirker) in Scandinavia, Germany, and the Baltic region, built during the Hanseatic League days. The only older buildings in the world are a few built in China. Those wooden churches, and all the other old wooden buildings in northern climes, are both old and well insulated. The little I remember from the article is that the wood was cured for about four years before it was used in construction, and then the wood is mounted on top of stone. Using cured, or aged, wood, prevents the wood from changing shape after it is used, and its dryness helps prevent rotting. Even so, any rotten wood that did develop was removed and replaced. And thus, we still today have the 800+ year old wooden churches in that part of the world.

I visited my relatives in the old country, who lived in wooden houses built in the 1700s, and they were plenty warm enough. I mean, think about it. It is only logical that the people living in northern climes would want to have insulated housing, especially since central heating with gas is a relatively recent invention, and they have been living there for many centuries.

5 ( +5 / -0 )

Properties, certainly in the cities, are not built to last because they start depreciating as soon as the first buyer steps in the door.

In Europe, properties are commonly maintained, added to, and refurbished. They typically increase in value over time. My house was built (of brick) in the 1950s. It will still be here in the 2050s. Partly due to choice of materials, quakes, and the economics of construction, the average (modern) Japanese house would not be expected to last for 100 years.

If it makes you feel better, my unheated toilet is like an ice box in winter and a sauna during heatwaves. My double glazing was bodged by a previous owner and has plenty of gaps around it. And my energy supplier is forcing a smart meter on me, lying that my old meter has reached the end of its life.

I would point out that uPVC is plastic, which JT articles and commenters regularly demand be banned.

1 ( +1 / -0 )

Seriously, what is the history of thin walled construction in Japan? People in other countries in northern climes have been living in buildings with thicker walls for centuries, so what happened to Japan?

1 ( +1 / -0 )

Houses were traditionally built to be easily rebuilt, due to various natural disasters that made more permanent infastructure not so viable.

-2 ( +0 / -2 )

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