We are currently in the process of removing our old brick fireplace facade and preparing for a hearthstone wood burning insert. We have been slowly removing the brick and have discovered a section with insulation behind the brick. We don't understand the purpose of this, but it does explained why we were getting a smokey smell in the house when we did use the fireplace. I'm curious if anyone could eplaine the reason behind this so we can properly replace the facade with stacked stone. I have included pictures of what we started with and where we are currently. Thank you for any help in advance.