Typically, the IR energy is absorbed by the glass as heat.
Glass does not block ultraviolet light. You get a sunburn by exposure to excessive ultraviolet light.
Ultraviolet and Infrared.
Ultraviolet is a type of electromagnetic radiation. It has a higher frequency than visible light. It is called ultraviolet because violet light has the highest energy of the colours. UV light has more energy, and hence ultraviolet.
Ultraviolet light can pass through glass, but the amount and type of UV (eg UVA, UVB etc) transmitted depends on the type and thickness of the glass, any coatings and laminates.
Ultraviolet light, x-rays, and gamma rays carry more energy than visible light. (That's why ultraviolet light does nasty things to skin cells, and x-rays and gamma rays can penetrate solids.)
Ultraviolet radiation is of higher energy than visible light. Ultra-violet suggests that it is above violet in the spectrum, and the colour violet is the uppermost region of visible light.
Ultraviolet light has a greater energy per photon.
Some of it reflects (bounces) back to the source. Some of it is absorbed into the glass, and never heard from again. The rest of it passes through the glass and continues on its way.
Yes, there is some reflected light lost at each interface, which will lower the intensity of the beam. The polarization may be affected too. Depending on the glass there might be a color shift.
Heat
An atom could put off ultraviolet light if it was excited by ultraviolet light at the appropriate energy level. Atoms emit light when they are hit with the exact energy of photon to promote electrons to higher orbitals. The light is emitted as the electron drops back to its ground state.