KYOTO -- From the outside, Junko Shimomura's condominium looks much like the hundreds of other apartments in the highrises that line the Kamo River in Kyoto's Ukyo Ward. But the interior -- with the living room's mukunoki wooden floor sealed with natural paulownia-tree oil and the terra-cotta tiles on the floor below the window -- has an ambience far more inviting than that offered by the average Japanese condominium.

The condominium owes its unique interior to the renovations Shimomura and her husband have carried out since they moved in last May. Renovating is nothing new, but what the couple have attempted to do is "eco-reform" their residence -- or replace existing construction materials and fixtures with natural ones.

Eco-reform has come increasingly into the spotlight in recent years as Japan struggles to deal with its ever-growing piles of trash. According to Harumi Matsuno, a member of the Citizens Environmental Foundation, a Kyoto-based civic group, construction materials account for 25 percent of all the waste produced in this country. Repairing or renovating houses or apartments instead of demolishing them, she says, can play a significant role in reducing this figure.

"Houses in recent years are scrapped and rebuilt in a 25-year cycle, and today's building materials are made to last only about that long," says Matsuno, who studied Western architecture at university. "Houses in Japan, however, used to be repaired and renovated for many generations."

The natural materials used in eco-reformed homes also offer a solution to "sick-house syndrome," or illnesses caused by unhealthy building materials, as they emit no toxic gases and cause far fewer allergic reactions.

The benefits are just as much psychological as physical, however. Shimomura says that living in a place surrounded by natural materials gives her much comfort.

"Getting down on my hands and knees to clean the floor used to be a real chore," she says, "but I love doing it here; it makes me feel so good.

"This place is not only good for the environment but also good for our souls."

While some eco-reformers are professionals, many, like the Shimomuras, are enthusiastic DIY-ers. Shimomura got started on her condominium by reading up on the many different kinds of building materials available and discussing options with experts. While the wooden floor of their 23-year-old condominium was installed by professionals, she and her husband peeled off the vinyl-coated wallpaper and, with the help of friends, plastered with diatomaceous earth (a kind of pulverized sedimentary rock) the walls of one of the rooms and the corridor of their home themselves.

"Diatomaceous earth absorbs moisture from the air, which is important in houses and apartments with poor air circulation," Shimomura says. "This wall now 'breathes'."

Although Shimomura has for many years practiced eco-friendly living by reusing goods and purchasing environmentally friendly products, it was not until she decided to buy a condominium and began researching suitable options that she became aware of the eco-house concept. Her interest piqued, she read books on the subject and also attended a number of meetings about eco-homes, one of which was organized by the Citizens Environmental Foundation, which started a study group on eco-housing in April 1997.

After an in-depth study of the issue, the group compiled a booklet in April on the eco-reform of houses and apartments. It features eight case-studies, including a traditional Japanese house, an apartment and a prefabricated house. One describes how a 1912 tenement house in Osaka was saved from demolition and instead renovated, with solar panels installed on the roof.

Matsuno, who serves as a coordinator of the eco-housing study group and lives in a 90-year old wooden Kyoto University dormitory, says that traditional Japanese houses, including tenement houses and machi-ya tradesmen's houses, embody the wisdom of environmentally friendly living as they last so long and were built with natural, locally available materials.

"Japanese people used to live in greater harmony with nature. We need to study traditional Japanese houses more closely to find what parts of their wisdom can be applied to today's houses."