Building materials attenuate the microwaves used for telecommunication depending on their composition and thickness. Modern windows contain glass with a metallic coating. This might cause a low quality of cell phone reception inside some buildings. In order to improve the transmission of microwaves used for telecommunication through modern glazing, a novel patterned coating was developed. In this work, the morphology and chemical composition of the pattern was characterized. The attenuation to microwaves of coated, uncoated and patterned glass was measured and simulated. The effect of the size of the air gap of a double glazing was studied by numerical simulation. Typical attenuation to the microwaves of building materials used for telecommunications is presented and compared to our newly developed patterned coating. In this paper, we demonstrate that a specific laser treatment on a conductive coating can strongly improve its performances regarding the transmission of microwaves.