you guys are going to make your computers work too hard to render simple window glass. when I look through a window there isn't much refraction going on because the glass is not really that thick. Refraction is going to really increase you render time AND render noise. Just use glossy and transparent nodes for your glass. Roughness is the parameter that will make it look frosted. I'll post some examples but here is some simple glass used on the car windows. Renders fast and I can't tell that it's not "correct" with refraction.

W10, Ryzen 5 1600x, 16Gb,RTX2060Super+GTX980, PP11, 11.3.740