Model thiol-click glassy networks with low shrinkage and sharp glass transition temperatures are studied down to cryogenic temperatures to relate viscoelastic damping to changes in microscopic hole volume. Networks synthesized by polymerization of divinyl sulfone with pentaerythritol tetrakis(3-mercaptopropionate) (PETMP), trimethylolpropane tris(3-mercaptopropionate) (TMPTMP), and pentaerythritol tetrakis(2-mercaptoacetate) (PETT) were studied to similar to 50 K using positron annihilation and thermal analysis methods. Across the glass transition temperature, overall volume expansivity is dominated by expansion of microscopic holes. Beneath T-g, holes contract upon cooling and then become static with negligible expansivity at temperatures well above 0 K. A trade-off between complete rigidity of static free volume and viscoelastic damping ability below T-g is discussed. All samples show moderate damping (tan delta > 0.05), and one sample exhibits a prominent beta-transition in its viscoelastic loss spectra. These results indicate the potential for tuning the molecular design of low-temperature glassy networks to optimally incorporate damping with low shrinkage.