Study on Thermal Insulation Retrofit of Wooden Rental Apartment Housing in Cold Region

This study investigated indoor environmental and thermal insulation retrofit performance in wooden rental apartment housing in Sapporo. Questionnaire surveys revealed that about 30% of residents were dissatisfied with noise, coldness, and condensation. Field measurements showed that living-room temperatures were generally maintained above 20°C, while bedroom temperatures tended to be lower. Indoor CO2 concentrations suggested insufficient ventilation. Although airtightness performance improved after thermal insulation retrofits, measured Q-values in many apartments were lower than the designed Q-values. These results suggest that current performance evaluation methods may overestimate the actual thermal performance of apartments under real occupancy conditions.