
Hi,
There is no way to determine the emissivity of materials from a Landsat-8 classification.
Typical values for asphalt are around 0.95, rough concrete is around 0.94, but aged or dirty materials are somewhat higher.
Typical values for vegetation are 0.97 - 0.98, for bare soil 0.96 to 0.97, water around 0.985 (all values for the 11 - 12 µm spectrum).
Hope this helps,
Sarah