TherMix is a chimney insulating product used to fill the space between a replacement chimney liner and the existing masonry chimney. Ready-mix formula cures into a lightweight semi-hard mass that insulates the replacement liner and dissipates the intense heat that occurs in the event of a chimney fire.
To calculate the amount of TherMix needed, please refer to the PDF at this link:
TherMix is a lightweight masonry insulation that is mixed with water and poured between the liner and the chimney shell. Each UPS-able boxed bag makes 3.25 cubic feet of material. Most chimneys require 2 to 3 bags.