With the construction of a heated-grid gauge, whose grid temperature can be varied independent of the electron emission, the two major barriers against precise pressure measurements in the extremely high vacuum (XHV) region, i.e., electron-stimulated-desorption neutrals and outgassing, have been successfully separated. In XHV, these two processes are both dominated by hydrogen molecules, while their strengths depend strongly on the grid temperature and the grid material. At elevated temperatures, outgassing caused by the out-diffusion of hydrogen atoms dissolved in the grid begin to dominate. This suggests use of a metal with low hydrogen solubility for XHV-compatible grid material.