It's a winter morning in Tokyo and the thermometer on your wall has gone sub-zero. You fumble for the heater, but it's hard to see through your icy breath. Not for the first time since you've been living here, you wonder why houses and apartments in Japan are so cold — and what you can do to make your abode a little less freezing.

For those who come from a land of central heating (or very mild winters), the discomfort of the cold months in Japan can be a surprise. Unlike buildings in large parts of the United States, Europe and even neighboring South Korea, Japanese houses, apartments and office blocks typically do not have any form of central or underfloor heat. They are as chilly as cellars from November through to March.

A notable exception is Hokkaido; buildings in the far, frigid north often have central heating, double- or triple-glazing and proper insulation — something that is a foreign concept on the mainland. 

Why Japanese buildings are icy in winter

There are a number of theories, but the biggest involves the insulation — or the lack thereof. For centuries, Japanese houses have been built with the country's sweltering, steamy summers in mind. Airflow and ventilation have, we are told, been prioritised over any kind of comfort in the colder months to prevent both the building and its occupants perishing in the humid heat.

Windows and glass doors are found in abundance. Effective insulation, on the other hand, is rare to non-existent; those who seek it will soon encounter the myth that the stuff makes construction much more expensive. 

There's also the prevailing notion that since Japanese buildings do not last long, there's no point bothering with extras like insulation. Many Japanese structures are torn down after just a few decades of existence to make way for new, more stylish successors; some have their fate sealed by earthquakes and tsunamis.

The preference for space heating (where you warm up a small area as opposed to the whole building) is often also attributed to safety considerations, though the extent of the risk of other types of heating has been called into question. 

In addition to being an integral way of cultivating the nation's prized quality of endurance, the practice of heating only small areas in an otherwise cold living space is also punted as a way to save energy — though anyone who's received a utility bill in winter will surely raise an eyebrow at this assertion. Cost aside, moving from a warm room to one that's more like a fridge actually creates the risk of heat shock; this is thought to be less than wonderful for the human body. 

Without delving into the more serious health concerns, you're no doubt familiar with the blue knuckles and cold ankles that characterise winter and have already invested in a few heaters (gas, electric and paraffin being the options, in order of preference), as well as a solid stock of thermals, to get through the big chill.

But unless you're in line to build a new house (particularly a passive house), you're likely going to have to take a few more creative steps to minimise the freeze and maximise the comfort. 

Six tips to vanquish the cold

Try some of these suggestions to thaw out.

1. DIY insulate your windows

You may not be able to replace those single-pane, unglazed glass windows, but you can do a few things to cut the freeze factor.

For a start, you can cover some or all of them with either bubblewrap or special insulation sheets that are sold at home centres and sometimes large supermarkets. You use a hairdryer to "melt" some of these sheets (not the bubble wrap) onto the inside glass; it can be peeled off when summer rolls around. Look for anything that says 窓ガラス発熱シート (mado garasu hatsu netsu sheeto) or something similar for an idea of what's available, and follow the (usually pictorial) directions to attach the sheets to your windows.

Finish the home insulation job by putting metal-friendly tape over the metal rims of your windows, and then around the windows to create a seal between them and the walls. The added warmth will offset the dubious aesthetic. 

2. Stop up the doors

Windows and non-essential doors can be fitted with draft exclusion boards — these are available at home centres and some supermarkets for a couple of thousand yen a pop (maybe less). Look out for すきま風ストップボード (sukima kaze sutoppu bo-do) or あったかボード (attaka bo-do) and follow the instructions (pictorial, usually) on the product.

3. Find and fill vents

If there are any vents in your apartment or house, consider temporarily sealing them for the winter. You can do this easily by removing the grill, filling the space with some newspaper or rags, and covering it up with a thin piece of wood or plastic (which you should be able to find at the local 100-yen store).

Just make sure that the vents are not critical ventilation points before you block them — for example, anything above or near your gas cooker should not be sealed! 

4. Upgrade your curtains

Buying thicker curtains that are designed for winter can make a difference to the temperature in your room. They can also block out excess light, which is an added bonus. Check your nearest home centre for styles, sizes and prices.

5. Use your aircon to dry the laundry

Japanese airconditioners come with a heating function, which makes them a fairly efficient way of warming up a room (if you keep the temperature and flow moderate, anyway). The downside (other than the energy consumption) is the intense dryness they can cause.

To avoid this, hang your washing up to dry in the room you're heating. That way, you avoid icicle-clad jeans and get a dehumidifier at the same time.

6. Invest in a kotatsu and hot carpets

If you haven't yet, consider getting a low table that comes with a built-in heater and blanket. You can pick up a kotatsu for as little as a few thousand yen — and it's money well spent.

Japan's small, portable electric carpets, known as "hotto ka-petto", are another winner in the winter months. Of course, you might also want an electric blanket for your bed. You can find both of these items at home centres and some supermarkets.

This article was first published on REthink Tokyo.

Similar to this: 

Japanese traditions for sustainable building

MUJI releases new tiny home design

Old and new come together in Japanese house renovation