The amount of fluorocarbons involved in building insulation foams as blowing agents is discussed with numerical analysis and measured data in this paper. The diffusion process of fluorocarbons in insulation foams can be expressed as a simple one dimensional diffusion equation. Effective diffusivity and initial concentration of CFCs and HCFCs are necessary to calculate the decrease of concentration with the analytical solution of the diffusion equation. The initial concentration can be obtained from the information of manufactures. In order to study the effective diffusivity, the calculated concentration of CFCs and HCFCs is compared to the measured data. Many samples were collected in various areas in Japan and their CFCs and HCFCs concentrations were measured by the gas chromatography method. The emission rate of CFCs and HCFCs was estimated by the analytical solutions with the effective diffusivity and initial concentration and the database of remained volume for various ages and areas is obtained in this paper. The total amount of CFCs and HCFCs can be estimated with this database and another database of the building insulation stock that will be discussed in Part 2.