Wood products function as carbon storage even after being harvested from forests. This has garnered attention in relevance to climate change countermeasures. In the progress of efforts toward climate change mitigation by private companies, the effective use of wood products has been an important measure. However, the methodology for accounting carbon stocks in wood products for private companies has not been established. Therefore, this study investigated methods for estimating carbon stocks in wood products used in wooden houses built by private enterprises, targeting a major company in the Japanese building industry. The results indicated that both the direct inventory method and flux data method (FDM) were applicable for estimating the carbon stocks. These two methods use data that can be obtained from many other building companies, thus, indicating high versatility. The log-normal, Weibull, normal, and logistic distributions, in descending order, proved to be suitable lifetime functions of wooden houses under the FDM, with a half-life of 66-101 years. It is important to continuously acquire time-series data on the floor areas of both newly built and existing houses and the amount of wood products used to improve the accuracy of estimates and explore future predictions.
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