One of our main bugbears with used houses is the obsession with a southern exposure. Though we perfectly understand the rationale–Japan is in the northern hemisphere and thus a southern facade provides more natural heating in the wintertime–we can’t fathom the insistence of builders and designers that all rooms in a house will face south and all “utilities,” meaning bathrooms and kitchen, will be located on the north side of the structure. Given the normally small plots of land in Japan, this results in a kind of domino distribution: all houses in a development “face” south, which inevitably means facing the “north” side of your neighbor. When we’ve asked builders about orienting a house toward the west or even north in order to take advantage of some attractive natural feature of the land, we’re invariably met with consternation and concern. It’s entirely possible, they say, but inadvisable. Some things just aren’t done.

Our reasons for shunning southern exposures are mostly aesthetic, but a recent article in the Tokyo Shimbun suggests that maybe southern exposures are not economical or even healthy. The University of Tokyo Engineering Department built an experimental house on the roof of one of its buildings to study the effect of direct sunlight on interior environments. Like almost all modern Japanese housing, the part of the building facing south had large plate glass windows so as to allow more light in. On sunny winter days when the exterior temperature was 10 degrees C, the interior temperature was as much as 35 degrees C, which is actually bad for the people who live there. In essence, the large windows make it difficult to control the interior temperature, which means the home owner may actually use more energy. According to the professor in charge of the project, it depends on the type of glass that is used, but in most houses the windows allow visible and near infrared light to pass into the house, where it is reflected off of the floor in the form of far infrared light, warming the room. Far infrared light cannot pass back out the window and thus more heat is trapped in the room. Direct sunlight contains a great deal of energy. Moreover, at night, when temperatures drop even further and there is no sunlight, more heat escapes from the house because of these big windows. Read More