A self-consistent set of thermochemical parameters for 47 molecules in the Si-O-H system are obtained from a combination of ab initio electronic structure calculations and empirical corrections. Both stable and radical species are included in the study. Good agreement between the calculations and experimental data for the heat of formation of SiO is found, while the prediction for SiO2 suggests that accepted literature values for the heat of formation of this molecule are too low, in agreement with a recently reported experimental measurement. Results for other species in this system are also compared with the literature and are found to be in acceptable agreement. Polynomial fits of the predicted thermodynamic data over the 300-4000 K temperature range are included in the supporting information.