Development and test of a combined radon sub-slab suction and sub-slab drainage system

To ensure a healthy indoor environment, the indoor air level of the radioactive gas radon must be kept low according to the WHO. This can be achieved by installing a radon sub-slab suction system. In buildings with a basement at the same time a sub-slab drainage system is often necessary. This paper describes results from a project, aiming to combine a radon sub-slab suction system with a sub-slab drainage system. A combined system will minimize the number of pipes when constructing new buildings and will also provide an easier retrofitting method for adding a radon sub-slab suction system to buildings with an existing sub-slab drainage system. In the project, it was found that the combination of the two functionalities required an airtight system to lower the pressure under the ground slab, an unhampered drainage of ground water and a prevention of odour from the drains. To meet these requirements, a prototype of a well with a water trap, a water outlet and a separate suction pipe for the air outlet was developed. A low voltage fan was installed in the suction pipe. The system was installed in a detached house with a 104 m2 basement. After installation, the pressure reduction over the ground slab in the basement was measured to be able to investigate the effect of the suction system independently of the radon exposure. The results showed a reduction of the pressure in the farthest corners under the ground slab by approximately 0.6 to 1.9 Pa compared to the pressure over the ground slab. We concluded that a combined radon sub-slab suction and sub-slab drainage system is possible with the designed well, although the use of a stronger fan will be necessary to meet the identified test objective of pressure reduction ΔP ≥ 1-3 Pa.