I have been trying to understand this concept to identify on the best option to reduce temperature in my room.

I have read few article which stated that glass is transparent to IR radiation. ie Beyond the range of UV light (wavelength >400 nm), the energy of visible and infrared light are not enough to excite the electrons and most of the incident light gets transmitted. Thus glass appears transparent to visible and infrared light. Glass Opaque to IR

However, contrary to it I saw few article which gave proof of IR imaging where a sunglass (worn by a person) appeared black; which indicates that IR radiation is absorbed in the glass.

So which of these two is correct? Any anyone help me in understanding with logical reasoning and help me out for application of this concept to a real world problem.