We measured and analyzed the building penetration losses for four different kinds of facades as a function of the incidence angle and polarization at 3.5 GHz, which is a frequency of interest for fifth generation (5G) communication systems. Results show that the attenuation may vary up to 8 dB with the incidence angle, which justifies the need for an angular characterization of the penetration losses, going beyond the simpler characterization used for normal incidence. We also found that there is a relevant polarization dependence of this attenuation, as electromagnetic theory predicts for wave transmission across flat discontinuities and even across flat dielectric slabs. Results would be of interest for the network design of future 5G base stations using orthogonal polarizations.