Influence of Energy-saving Renovation Plan on the Hygrothermal Distribution Inside Kyo-machiya Soil Walls Considering their Moisture Buffering Effect

Abstract

Kyo-machiya are traditional townhouses in Kyoto that represent an important aspect of cultural heritage preservation. Because of the poor thermal insulation performance, they require energy-saving renovations. However, their unique soil walls possess a moisture-buffering effect that can be strongly influenced by the applied renovation plan and are expected to remain functional even after renovation. Conventional renovation methods apply an inside vapor barrier to the interior insulation to prevent condensation between the insulation and wall; however, applying this barrier may hinder the buffering effect and deteriorate the unique interior appearance of the soil wall. Therefore, we conducted a case study on the hygrothermal environment of a typical Kyo-machiya structure in winter when the moisture generated by indoor activities was adsorbed by soil walls. We used the finite difference method to divide the various renovated envelope systems into thin layers and calculated the temperature and humidity distributions. Based on these results, we propose the use of exterior insulation for renovations, owing to its excellent thermal performance. However, if the space between the adjacent buildings is insufficient, interior insulation can be applied without a vapor barrier.