Thursday, 9 September 2010

Heat island 2

As I was saying a week ago, the heat island effect in Tokyo is a big problem, especially with the minimum temperatures.  Last week while we were away one night had a minimum of 29 degrees!
Urban heat islands is something that comes up a lot in high school geography classes - buildings & footpaths absorbing heat during the day and not enough vegetation to have much evapo-transpiration cooling are usually given as the main factors. 

Inefficient energy usage - insulation

Most of Tokyo was destroyed in WW2 fire bombings and after the war cheap quality,  four and five storey apartments - often built as government or company accommodation - were hastily constructed to house the workers of  "new" Tokyo. This continued through to the sixties.     The living conditions in these apartments were often pretty basic: cramped, poorly insulated ferro concrete, prone to damp and mould,  little storage space - much of the kitchen storage tended to be above head height.  The poor insulation makes for hot summers, cold winters and high sales of aircons. The picture on the left, taken a couple of years ago shows a typical example of this kind of apartment block. ( there are no lifts in these buildings.)

Gradually these buildings are being replaced - with what are generally more spacious apartments, usually with lifts which makes a huge improvement in the quality of life, especially for older people.  But I'm not convinced that there is much improvement in insulation.   Insulation is included in building codes but as far as I can tell, compliance is still voluntary. Our building is 9 years old,  and I suspect has zero insulation. We're on the top floor and on the nights where 27 was the recorded minimum, it was usually at least 33 degrees at 6.30 am in our place....very hot.  It's no wonder most people in the building have been running aircon constantly, air con that spews heat out into the the surrounding air. It's  ironic - heating the outside to make the inside cooler.

With improved technology for earthquake resistance, buildings are getting taller.  The infrastructure in Tokyo supports denser living, and not having a long commute to dormitory suburbs makes for an easier life.  The buildings below,  both nearby,  replace buildings that were two or three stories high.  Neither are inhabited yet, but given a few weeks or months  these pieces of land,  which formerly would have two or  three or so aircon on it,  will now likely have more than 20 each....

Old style apartment with garden
In addition to all the extra aicon, another  feature of the new buildings is that they seem to take up almost the entire available land area.  There are apparently  laws against this, including laws that mandate height ratios, but either they are guidelines, or people can get away with not complying.   The older style apartments typically had reasonable garden space. (see left)  The apartments in front and behind got light and sun to dry futons and clothes on the balcony, older people in the building had a ready made hobby, the vegetation kept the area cooler and there was capacity to absorb water reducing storm water run off and flooding.  The building below was built about 3 years ago and replaced two buildings that were very similar to the one on the left.   I am not sure what the insulation is like, but all rooms have aircon.  The new building  has almost no space for vegetation (there is a small strip on two sides that can't be seen on the picture).   Tokyo Metropolitan Govt. has been talking about roof top gardens as a way to combat increasing temperatures, though there is no evidence of it on this building.
 It seems like much of the motivation for no vegetation is that people want cars.  Before the building on the left was  built, when it was it was two side by side 4 storey apartment blocks, there were no car parking spaces.  It now has 27.  Each car parking space fits three cars: the cars pile up on top of each other, get stored underground are lifted with hydraulic lifts when they need to be used. (see the picture below.)  Japanese govt. statistics household car ownership in Tokyo has fallen slightly this year, so perhaps the north east of Tokyo is unrepresentative, or perhaps the statistics aren't showing the reality...
Something else that you can see from the the pictures is the asphalt surfaces - something that is always associated with urban heat islands. A friend who bought a house recently had to put her foot down very firmly to have grass around her house - the construction company wanted to concrete the lot - and looking around the neighbourhood, it seems like most people went with the concrete....
  Japan has actually been making really good progress with developing ceramic blends for pavements and other hard surface areas, that absorb large amounts of water and release it over time. (2)  It has the dual advantage of reducing run off and and increasing evapo-transpiration.  It seems like it might be promising for roof surfaces too. I am not sure if it is available commercially yet. The construction companies might need better kickbacks to consider using it.....

There is also a lot of research happening on cooling systems esp. using evaporation.   In the summer here you can often see shop keepers and home-owners splashing the footpath with water to cool it down. It's low tech but very effective, as is growing plants to keep the heat down.  There are lots of  higher tech options to reduce the heat and air con emissions including double roofing. (3).  Regrettably few seem to be being adopted...
Plants to beat the heat growing outside a house in Yanaka.
Hopefully they don't get killed by the neighbours aircon...
And so.... the plan for this household.... no air con for next year.    Instead,  an attempt to make the balcony more like a forest and less like a barren wasteland. The idea of rigging up an evaporation system is appealing but I don't think it would go down well with the neighbours below when they want to dry their futons...Splashing water on the balcony might have to suffice instead.

1.  Insulation & building codes
2. Footpath technology   

3. Cooling rooves.

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