ZEMCH 2019 International Conference Proceedings April.2020 | Page 17
As a result of measuring the thermal transmittance of the window itself before applying the
glazing, the average of 3.333 (Case C) and 0.945 (Case D) was 1.97. After application of the attached
glazing, the thermal transmittance of the window was measured as 2.475 (Case C), 0.842 (Case D), 1.56.
The ventilation volume reduction was 25.74%, 10.90%, and 18.59% on average. Through these, it was
confirmed that the airtightness performance of the windows improved by the application of attached
glazing. Also, it was analyzed that the higher the heat transmission rate of the window itself, the higher
the decrease rate.
Thermal performance of windows and doors with attached glazing compared with domestic and
international standards are shown in Table 6. In the case of Korean, three windows have improved
thermal performance by grade 1 or higher. In the Spanish standard, three windows have improved the
airtightness performance by level 1 or higher, and level 2 in case C. In case of the Japanese standard,
Case B was upgraded by 1, and all but Case C were analyzed as the highest grade. Although there is a
difference depending on the application criteria and the performance of the windows, it is confirmed
that the application of the attached glazing in the case of the windows which is not the highest grade
improves the thermal performance grade of grade 1 or more.
Table 4. Change of thermal grade of windows by application of attached glazing
Standard
Korea
Spain
Japan
Case A
2 → 1
A → A
★★★★→
★★★★
Case B
4 → 4
D → C
★★★☆→
★★★★
Case C
5 → 4
F → C
★★★☆→
★★★☆
Case D
1 → 1
A → A
★★★★→
★★★★
Case E
3 → 2
B → A
★★★★→
★★★★
4. Conclusions
In this study, we propose techniques to improve the performance of windows already installed in
existing buildings and analyze their performance. As a result of applying windbreak, a technology to
improve the airtightness performance of windows, the ventilation volume of windows decreased by
53.35%. The results are different depending on the performance of windows and international
standards. In order for the sliding window to open and close, a regular spacing of gap is required
between the sash and the window frame. This space remains open even when the window is closed,
resulting in direct heat loss. Mohair is usually applied to prevent the inflow of outside air through
thisspace, but windows that have been used for a certain period of time cannot function due to
deterioration of durability due to friction of mohair contacts. The windbreak is attached to the indoor
sash surface to directly block the air inflow path between the sash and the window frame, thus
improving the airtightness performance.
The application of attached glazing, the technology to improve the thermal performance of
windows, reduced the average heat transmission rate of windows by 18.59%. Also, it was analyzed that
the higher the heat transmission rate of the window itself, the higher the decrease rate. This result can
be different depending on the thermal performance standards of the each country, but in the case of
windows that are not the highest grade, it is confirmed that the majority of windows are improved by
the thermal performance grade of grade 1 or more. It is analyzed that the attached glazing is applied to
the window glass which is thermally weak compared to the building exterior wall, effectively
improving the heat permeability. The thickness of attached glazing used in this study was 3 mm. If the
thicker attached glazing is installed with a wider air layer, the improvement in thermal transmittance
rate can be higher.
In this study, we verified the improvement of window performance through the installation of
windbreak and attached glazing. In the future, it will be applied to more various types of windows to
increase the reliability of technical performance. In addition, experiments on long‐term performance
changes and durability changes should be conducted to improve the technologies.
Imroving thermal and airtightness performance of windows installed in existing buildings
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