Napoleon 36 Inch Updated Altitude X Direct Vent Gas Fireplace

No, the Altitude X models are considered "zero clearance" units, meaning they can be installed within their own framed enclosures.  Such models usually can be placed within a wooden enclosure, and the "zero clearance" refers to the fact they can be placed directly on a wood platform or subfloor.   Please note there are clearances to consider around the sides, top, and back, as well as possible requirements for noncombustible materials around and above the front of the fireplace.  No existing chimney is required because this fireplace can use either rigid or flexible 5" inside diameter/8" outside diameter double-wall gas vent pipe, and it can go either vertically above the roof or horizontally to an exterior wall (with limitations depending on the distance needed to get to the termination point).