Condensation risk-based applicability analysis and design of a dynamic thermal insulation window with ventilated airflow in different climates

Abstract

The exhaust air insulation glazing system (EAIG) integrates exhaust air heat recovery and dynamic insulation to minimize heat loss/gain through the window by allowing the exhaust air to be ventilated through the air gap between two glass panels. However, condensation may form on the internal glazing surface of EAIG during winter. How to prevent the occurrence of condensation and improve technical feasibility of EAIG for various climatic conditions has not been addressed. A numerical model was developed to determine the hourly glazing surface temperatures of EAIG and identify whether condensation will form or not during winter. The condensation probability of EAIG was quantitatively estimated considering various window orientations and climatic conditions. Furthermore, the effectiveness of some potential measures for preventing condensation in EAIG was also investigated. The results indicate that outdoor weather conditions significantly influence the condensation of EAIG. For a climate with a relatively mild winter, slight condensation occurs within the EAIG, while in severe cold climate, long-term condensation with a probability of 45.4 % occurs, which detrimentally affects the practical application of EAIG. Moreover, reducing indoor humidity and adding a low-e coating can effectively reduce condensation probability and expand technical feasibility of EAIG for various climatic conditions. In severe cold climates, the condensation probability decreases from 45.5 % to 6.5 % when employing an additional low-e coating. The findings in this study are beneficial to providing a design guideline for engineers and architectural designers, and enhancing the applicability of EAIG in various climatic conditions.