The past few decades have shown a veritable explosion of new versions of energy-saving windows and coated window panes. In the wake of this, problems with radio communications into and from within buildings has arisen. However, this unexpected attenuation of radio signals may also be used to shield a facility from incoming intentional electromagnetic interference (IEMI). With the intention to investigate the shielding effectiveness (SE) of modern windows and window panes a two-year measurement campaign was launched mid-2014. Another, little investigated area is what happens to coated glass when irradiated by a high-power microwave (HPM) source. Shielding effectiveness has been measured for different types of energy saving windows and coated window panes both in a semi-anechoic chamber and in a reverberation chamber over the frequency range 1-18 GHz. The effects of HPM irradiation were studied by comparing SE measured before and after the pulsed 28 kV/m L-band irradiation. The main conclusion is that with the right choice of window the shielding effectiveness of a building can reach up 40-50 dB. In this paper we summarize these measurements and lessons learned from the measurement campaign.