Reducing the Electrical Cost of Radon Mitigation

During the year 200 1 there were severe electrical energy problems in California. There were several instances when localized electricity blackouts were imposed due insufficient power generation capabilities. In response some citizens simply disconnected their radon system, and several inquired as to the advisability of using a timer to interrupt the fan operation. In this paper I will present some data and analysis on the timedependent operation of a subslab depressurization system. The radon radiation concentration in the soils is assumed to follow a diffusion equation with a spatially uniform source and decay proportional to it magnitude. The diurnal temperature driven stack effect is approximated as a sinusoidal surface pressure of 0.1" water column while the mitigation system is a step function with amplitude of 1.0" water column. When the system operates, it will decrease the subsurface radon concentration on a time scale of 3-6 hours, dependent on soil porosity. Due to the lower magnitude of the stack effect, the subsurface radon concentration returns to equilibrium levels on a much slower time scale. The result is that a mitigation system need only operate for a portion of the day to effectively mitigate the radon infiltration. Some limited data support these predictions but more must be obtained before any change in protocols is considered.