Friday, December 03, 2010

Insulating a Japanese House for the Winter

For the most part, the Japanese still haven't discovered either central heating or double-glazed windows (another example of low-tech Japan). Not only that, but old Japanese houses are actually designed to be cold. Kerosene heaters and kotatsu are the obvious ways to heat up your home, but if your house is anything like ours, you'll need to do some extra work to keep that heat in.

Read on for hints on tape, bubble-wrap and various other solutions designed to stop you resorting to buying one of those monk-outfit/blanket/muu-muu things with arms.

The horrible relentless cold has just started to peek ferociously around our shouji screens this year, after a brilliantly long and hot summer. Our house is very old and has very thin walls. It also seems to suck cold air in through all the cupboards. Time for some preventative measures.

  •  Bubble-wrap
    • My toilet windows, minus curtain.
    • Possibly the most effective solution.
      Shouji screens do act as a primitive form of insulation to the heat-sapping windows prevalent in most Japanese places, but it's much more effective to give the windows themselves another layer. The Japanese way of doing this is with bubble-wrap. There's nothing special about it (unless you buy the fancy designs); it's just bubble-wrap (in fact, buying a roll of industrial-issue stuff would be much cheaper than getting the purpose-packaged stuff in housing stores). Stick it on the whole window/door and that alone will make a huge difference to the room temperature. Instead of radiating cold like an open fridge, your frosty windows will now be tamed and ready for action. Take that Japanese tendency to make 1/4 of the walls of a house out of single-pane glass!

  • Heat-applied insulation sheets
    • Usually found next to the bubble-wrap in home-stores, and advertised to be the most effective insulation idea ever, is some kind of plastic sheet which can be melted to your doors (as an alternative to bubble-wrap). The picture on the tube shows a hair-dryer, though I think an iron would be more fun. See the picture below for full details of your options.

These are the various things presented at my local hardware store. From left to right we have: 
  • Condensation Stopper Sheet, attach with water
  • Clear Window Glass Thermal Insulation Sheet, attach with water
  • Window Glass Heat Generation Sheet, attach with water
  • Window Glass Condensation Stopper Sheet, attach with water
  • Window Glass Clear Thermal Insulation Film, attach with heat
The star ratings indicate how efficient they are at:
  • Transparency  
  • Effectiveness of Heat Insulation
  • Condensation Deterrence 

  • Tape
    • A good idea is to add another layer to the anti-hero all-powerful metal window-frames that give off cold like it's going out of fashion. Bubble-wrap won't work here, so the Japanese sell a special kind of tape (although I'm sure a regular packing tape would probably work too) with which you can cover all the metal surfaces. This does make a difference, although it's not the prettiest thing in the world.

  •  More tape
    • After that, you'll want to ensure you have a good seal around all of your windows. Our house is wonky thanks to generations of earthquakes, and this is especially important for us. Don't think that just because your apartment or house is new that you'll escape this one, however. Even our old (modern) apartment had places where outside was clearly visible through gaps between the doors. Again, the solution is tape. You can buy a slightly padded roll for a couple of hundred yen which will stick across/between the joins in your doors/windows.

  • Block up those vents
    • I don't know if it's universal anymore, but in the dark-ages when our house was built it came complete with vents to the outside world (presumably to help circulate air in the summer). Being holes to outside, these are cold. The hundred-yen store is your friend for this one - the bigger stores, like Daiso etc, often have a DIY section. There you can either find pieces of wood or plastic which you can use in place of the vent (with some modification). Just take the grill out of the wall, stuff some newspaper in there and then screw the new article in place (some sealant or rubber is an optional bonus). It helps.



  • Draft excluders
    • They look stupid, but these things are designed to stop the draft from around the bottom of your windows and doors. It seems like there should be a better way than this - I'd go with the tape first, and this as a last resort.

  • Condensation absorbers
    • Quite a good idea to stop your tatami/door frame from getting damp and rotten. Place them at the bottom of the glass to catch the drips. Removable.

Still less revolutionary options of making your Japanese house warmer involve curtains (if you can brace yourself against Japan's exorbitant prices), and finding some kind of hippy wall-hanging to dangle in-front of your cupboards. Also: yakiniku/nabe in the living room anyone?

JapanProbe has a video of a batty old woman who has fearlessly covered the inside of her house in rags and old futons to keep out the cold. Well, she's in Hokkaido, so desperate times call for such measures... I guess.

Well, that's all we've got. If you have any bright ideas or success stories, please let us know in the comments.


  1. Good article! My house is around 40-45 years old and is a vacuum for cold air in the winter and a sucker for hot humid air in the summer!!!
    Low-tech Japan is and understatement!!!
    3rd-4th world is more like it!
    Add to the fact that the L.A.M.F~ING J government wants to add a 'green' tax this year Is beyond me!
    How about a upgrade/insulate your home tax-incentive program.
    I'm slowly adding insulation to my attic, and will eventually convert it to a storage area/loft.
    But finding a remodeler that knows anything about insulation has been a waste of time.

    Please more articles how to insulate old tsuchi-kabe houses.


    Freezing in Nara

  2. Thanks Anon. It's interesting to hear that you are insulating your attic space. I've not heard of anyone doing that. Please tell us more!

  3. These are great! We already use bubble wrap on the windows, but we should put it on the doors, too. And man, tape. Seriously. Ahh, the most technologically advanced country in the world...

  4. Anon1 has an attic. They have attics in Japan? I don't think I've ever seen one. I want an attic!

  5. This had the potential to be a good article, but I lost interest in the beginning with the "Japanese haven't yet discovered double glazing or central heating". If a Japanese house has double glazing it will be harder to cool in the summer, surely? And is central heating really so efficient?

  6. That's a bit harsh - there's still a lot of information after the line you didn't like. And double glazing works fine in the summer in every other country, why would it be any different in Japan?

  7. True. A little harsh, sorry about that. Wrong side of the bed yesterday.

  8. Double glazing would mean that the cold air won't escape in the summer when you turn on the air con.

  9. I think the basic principle that doesn't seem to be in default operation in Japan is *insulation*. Double glazing insulates in hot as well as cold weather.

  10. Thanks for the article, I was just wondering how to survive a winter in Japan (my Japanese is too bad to google where to buy an insulating tape here) - my flat is terrible, the sound of wind drafting around windowframes is waking me up at night! My suffering is doubled by the fact that I do know something about houses and I have done few reconstructions back in Europe. My hands are itching for some serious rebuilding every time I see all the details in my flat. But I am here for one winter only and the owner is not willing to share the expenses...

    I am not sure about the bubble wrap: From my point of view, the only way to make it work properly is putting two layers over each other and taping or gluing the rims together, creating pockets of insulating air. This is how those marketed insulating foils are supposed to work...

    Cheapo's solution for curtains: Buy the cheapest polyester blankets you can get, use them instead of curtains. Be careful not to touch electrical or gas heaters with them!

  11. Thanks for the idea. I am thinking of best double glazing for my bedroom; Noise free, house insulating, best quality, fairly priced windows.