To anyone who questions the need to clean prior to lining we just got called out for an insurance evaluation on a fireplace that was lined for a freestanding stove. The liner was put in chimney not cleaned and throat just stuffed with fiberglass. There was a chimney fire in the liner it set the old creosote off which ran down and then a ball of burning creosote soaked fiberglass fell into the old fireplace luckily the homeowners were home and put it out with a fire extinguisher but it could have been bad. We haven't gone out yet but i will take pics when i do