[en] New measuring methods performed using solid state detector systems can provide the means for cost-effective radon decay product metrology for the purposes of the investigation of radon problems in buildings. Accurate, low-cost spectrometric calibration in the measurement of decay products is a prerequisite for the successful implementation of such applications. For suitable source-detector geometries, practically all alpha absorption parameters for geometry and material used are known. In simple vacuum counting, the detection efficiency for a point source located on the detector axis can simply be calculated as the fractional subtended solid angle. Software has been developed, which extends the scope of this calculation method to include alpha energy absorption in the various parallel absorption layers comprised of filter and air and detector windows, producing, in this way, an energy efficiency spectrum from the few fundamental parameters for multiple nuclides. Slight uncertainties in the parameters can easily be ironed out by means of spectral shape matching. For the purposes of variable, source-specific calibration the nuclide efficiencies in the channels or spectral regions of interest, as well as the uncertainty ranges for the efficiencies, can likewise be determined by spectral shape matching, particularly in the case of the absence of good counting statistics. (orig.)