Laboratory assessment of flexible thin-film membranes as a passive barrier to radon gas diffusion

This paper presents the experimental results of utilizing a flexible thin-film membrane as a passive barrier to radon gas diffusion. Nine commercially available membranes of various compositions and thicknesses were evaluated as retardant to radon gas diffusion. The radon gas concentration ratios across the thin-film membranes alone and in combination with an adjacent concrete sample Žeffective diffusion coefficient. were measured in a laboratory system with state-of-the-art instrumentation. An 8.89-cm diameter, 10.2-cm thick concrete sample of standard composition Žw c 0.5 and cement:sand:gravel 1:2:4. was used to simulate a basement and slab-on-grade foundation typical of Wisconsin. The radon gas transport characteristics of this concrete sample Žporosity, permeability and diffusion. are documented. The experimentation has identified two superior flexible thin-film membranes that may be employed as effective barriers to radon gas diffusion. These include: Polyethylene Naphthalate Ž7.62 10 5 m. and Polyethylene Terephthalate Glycol, PETG Ž7.62 10 5 and 1.27 10 4 m. which had average diffusion coefficients, D, of 4.10 10 14 and 1.66 10 14 m2 s 1, respectively. Measurements of the effective membrane concrete diffusion coefficient yielded a further average reduction in D of 98% for the Polyethylene Naphthalate and 96% for the PETG. Details of the experimental set-ups and procedures are described. The results of this investigation have shown that the application of an effective thin-film membrane adjacent to an intact concrete slab can significantly reduce the diffusion of radon gas entry. Therefore, the employment of a flexible thin-film membrane should be considered as a viable radon reduction technology method for residential new construction.