Glass wool is a __________conductor of electricity.

Glass wool is produced in rolls or in slabs, with different thermal and mechanical properties. It may also be produced as a material that can be sprayed or applied in place, on the surface to be insulated.
They possess very low expansion property, remarkable thermal shock resistance, low thermal conductivity, excellent electrical insulation up to 1000 C, and excellent resistance to corrosion from molten metal. 
Hence, Glass wool is a poor conductor of electricity.