is glass a heat insulator?

yes.

It really depends on what type of glass you are referring to. For example, many different laboratory apparatuses are made of glass because the glass holds its heat very well once heated.

However, glass windows used in buildings are designed to be very efficient at keeping the temperature moderated between the inside and outside of the building.

I think that glass is more of a heat conductor than insulator because of its properties of heat. Glass will keep its thermal energy for a long time after it has received it from its source. Although glass might not be the best heat insulator, it is the best electrical insulator. For a long time in the United States, glass insulators were used on wooden poles to insulate telephone and electrical wires.

This is quite a tricky one but I think glass is a heat CONDUCTOR because when you touch the surface of glass, it feels cool because glass quickly conducts the heat away from your hand, compared with when you touch the surface of a good insulator like a piece of cloth - it feels warm

try experiemnting by putting one end of a glass rod or something in a fire and see how fast the heat gets to the other end but be careful!

Windows are double or triple glazed because the air (or sometimes an inert gas) between the panes is a better insulator.

Yes

Yep, its one of the reasons they still use it for windows, not just because they are see through.

yes (thats why people get double/triple glazed windows)

no, glass melts