1. Introduction

It is claimed that to prevent global warming greenhouse gases need to be reduced in the long term by 75 to 82%1. These figures might seem unrealistic in relationship to the pessimistic opinion that Japan could not meet the Kyoto Protocol promise to reduce greenhouse gases (GHG) by 6% in the year 2010 (average between 2008 and 2012, compared to 1990). However, the above-mentioned targets are essential to keep the average rise of atmosphere temperature to within 3.5/2.5 degrees Celsius respectively. Therefore, it is acceptable to consider them as the target for the advanced low- energy dwelling of today.

The majority of GHG is carbon dioxide (CO2) caused mainly by the consumption of conventional energies, not only fossil fuels but electricity. To find effective solutions in the field of urban housing, an experimental project was launched in June 2005, the target for which has been to reduce the energy-based environmental impact to a quarter of the original amount by remodelling an existing apartment dwelling and comparing it with a basic apartment. This could be realised through reducing energy consumption and wherever possible using sources of locally available renewable energy.

The project has taken place within Osaka Gas Company’s experimental housing, “NEXT21”, which was built in 1993 for the purpose of experimenting with gas equipment within a highly durable “open building” structure and flexible “infill”.

Dwelling no.301 was selected for the project. This dwelling unit was originally designed by architect Naomi Tachibana as a “Garden House”, which aimed at living in harmony with the natural environment. It enjoyed plenty of indoor / outdoor greenery, day-lighting and natural ventilation.

Many alternatives were examined from the available techniques. This paper describes the methods to remodel the dwelling to consume less energy as follows: