Interstitial hygrothermal analysis for retrofitting exterior concrete wall of modern heritage building in Korea

Retrofitting modern heritage buildings aims at not only energy conservation, but also restoration and preservation of an architectural artefact. However, if envelope construction is adjusted and HVAC systems are replaced, the temperature and humidity profiles and air-tightness can also be transitional, thus condensation could occur on the surface and/or inside the structure. It is continuously emphasized to assess retrofit measures' expected transitions in the hygrothermal performance of envelope and their potential condensation problems, prior to actual retrofit. The present study measured the surface moisture content of the concrete structure and built environment of three modern heritage buildings in Seoul. These results were used as the initial conditions for the hygrothermal analysis of insulations and vapor retarder. One modern heritage school was chosen for retrofit, then mock-up test, ISO 13788 steady-state analysis, and dynamic simulations by WUFI were used to analyze the risk of interstitial condensation in the exterior wall, according to the initial moisture content of concrete wall and whether the vapor retarder had been installed. For modern heritage buildings with fully dry concrete walls, the mock-up test verified that the risk of interstitial condensation between the concrete and insulation is low, regardless of whether the vapor retarder had been installed. Per ISO 13788 steady-state analysis and WUFI transient simulation, if PF board was used as the internal insulation for concrete exterior wall, the chance of interstitial condensation was also low, regardless of the initial moisture content and the use of a vapor retarder.

Automated summary

When retrofitting modern heritage buildings, it is important to assess the potential transitions in the hygrothermal performance of the building envelope to prevent condensation issues. In a study measuring surface moisture content in Seoul, it was found that with proper insulation and vapor retarder, the risk of interstitial condensation in the exterior walls of dry concrete buildings was low.