Verifying the use of classroom windows during the COVID-19 pandemic. The path to devising “tasuki opening” (“opening inner and outer windows on opposite sides”), which ventilates without losing the effectiveness of air conditioning.

We asked Shinya Yoshida, head of the Kanto Shin-Etsu Area, Development & Sales Department, Commercial Business Division and representative of all the members who worked on this, about the road to devising the "tasuki opening" ventilation method for a trade-off between "thermal insulation, thermal barrier and sound insulation = closed windows" and "ventilation = open windows," with cooperation from the Sales Division and the Development Division.

We first proposed installing inner windows in school facilities in 2019.
At this time, the Ministry of Education, Culture, Sports, Science and Technology (MEXT) was encouraging the installation of air conditioning in school facilities. We thought that inner windows would be optimal to increase the effectiveness of air conditioning and to realize higher energy efficiency, and started proposing this to elementary and junior high schools in the neighborhood. One aspect that made this product appealing is that local architectural product distributers can easily install it and so it contributes to regional business. However, it was a hard fight as we really didn't convey the merits of the product. This was because even we weren't certain that installing inner windows in classrooms would really be effective in terms of thermal insulation and sound insulation, even though we were the ones proposing the product. In principle, school classrooms have rows of windows on the outer wall side, while the corridor side is a simple partition wall with no capacity for thermal insulation or airtightness. Ultimately, how effective would it actually be to add inner windows only to the outer wall enclosing the classroom? This made it hard to persuade people.
In addition, the priority in the educational facilities field was quake-resistance retrofitting work, so there were few cases of thermal insulation improvement or installing inner windows in Japan, and it wasn't really accepted.

We had verified the effectiveness of installing inner windows in homes on many occasions, but we needed to verify whether their effectiveness was properly apparent in school classrooms and then convey that effectiveness if they were to be used as inner windows in school facilities.
As we were wracking our brains, we received a proposal from Ryuji Mochiduki, who worked with us on proposal activities and was responsible for development: why didn't we try collaborating with the Value Verification Center,* which acts as our in-house product verification division, to verify the product's effectiveness by installing inner windows in actual school facilities? We decided to put this into practice.

Elementary and junior high schools in Nagano Prefecture and Gunma Prefecture cooperated with us for the verification. We made the most of the Value Verification Center's knowledge and measured the effectiveness of the product's thermal insulation in classrooms with the inner windows installed and in classrooms with the existing aluminum sash windows (no inner windows) twice, in summer and in winter. Measuring on hotter days in the summer and colder days in the winter made the effectiveness of the inner windows evident. It was difficult to manage the schedule so we could gain effective measurements when school events were also taking place.

*The YKK AP Value Verification Center: A facility that carries out different types of verification of product values (performance, security, ease of use, comfort) on sites belonging to people who actually use the products. It supports YKK AP's Monozukuri by identifying hidden issues through verification that replicates everyday living environments and severe natural environments, the opinions of user monitors, and an understanding of user demands from survey data.

Effectiveness of thermal insulation and thermal barrier

From the results of the verification, we were able to confirm that the inner windows were more effective than expected, with a 38% decrease in air conditioning electricity bills in the summer and a 27% decrease in the amount of kerosene used in heaters in the winter in the classrooms with the inner windows when compared to the classrooms with the existing aluminum sash windows.

Currently, we are going ahead with a proposal to install inner windows in other school facilities based on this series of verification outcomes. We are working with not only the Sales Division, but also with the people responsible for development and the engineers to create a proposal that will interest these customers. We have achieved this outcome together by sharing the issues considered by the people on the front lines of sales with the people in charge of development and engineering, with the joint desire of improving children's learning environments.

As we solve social issues as a window manufacturer, there is always something we can do to contribute to users. We want to make the most of the knowledge we gained from verifying this product so that inner windows will be adopted by schools across the country. In addition, we hope to continue verifying products other than inner windows as they are used so we can realize a better environment in school facilities in the future, and further this for proposals for school facilities such as gymnasiums that act as evacuation shelters during disasters. Another aim for the future is to share the value of our windows in a variety of areas, not just school facilities.