Hello all, I am a new arrival to these parts with a standard masonry fireplace, been using it for years and even with the glass doors it’s a lost cause regarding heating anything unless your standing right in front of it.. I now understand why wing backed chairs were invented all those years ago LOL.. I pulled the trigger on a Hearthstone Clydesdale insert currently on order and will install it myself. I am prepping the chimney and firebox while awaiting delivery of Hearthstone’s Equine offering. Some details: 2000 Sqr Ft Ranch Firebox 42”w x 30”h x 30”`d Exterior Chimney 14 ft from top to damper opening The fireplace is a circa 1970’s monstrosity in my family room at one end of the house that opens to Kitchen followed by dinning room with 2 entry ways to living room and entry hall to the side or front of house. The bed rooms are at the other end down a center hall. I went with the Flex King Pro double wall liner with smooth interior and insulation kit. With the short chimney I figured smooth flow might help. I plan on lining the masonry firebox with sheetmetal insulated with ceramic wool between the sheet and the brick including the damper block off plate and flue top plate to create a dead air space for the insulated liner. The recent discussions surrounding fresh air intake has me thinking and left with more questions than answers. I have an ash pit. The chimney is on the outside of the house so the clean out door is outside. Is it worth the extra effort to install the OAK from the cleanout door to the firebox at the back of the inset I’m installing? Will I save much in warm house air going up the flue? I'm trying to wrap my head around the whole cold air drops/warm air rises thing. If the OAK terminates to the outside 2 feet lower than the fireplace will the cold outside air be drawn up into the firebox versus being drawn from the house air? note, the fireplace is on the windward side of the house with wind blowing against it most of the time and the house is moderately tight and insulated. I would like to have a better understanding on the outside air thing before I install my block off plates and seal up that ash pit door in the firebox. It seems that running some cheap flex vent from the cleanout door to the firebox would be an easy thing to do. I see no indication that the Clydesdale has a connection for an OAK so where does the air get drawn into the insert to go up the flue?? Thanks for you input.. Adding a few pics as well for clarity sake..