Question: Have just completed construction of a 3 season, insulated porch, size 14x18 with sloping ceiling- peak at 14' sloping to 8' . BTU calc comes out at about under 10k. Would like to add a gas fireplace, propane, direct vent (horizontal) to place on outside wall under a window with 39' sill height. Question - Is this feasible? Can you suggest vendors that supply small units that I can install. I would like to build my own mantle as well. Answer: THere are a number of units that vent at this height or lower. Heat n Glo comes to mind as one the would have some smaller units. The only concern is the fact that many units must terminate a certain distance from a openable window. Perhaps your windows do not open. Even if they do, you might be able to get around this one by extending the pipe out a bit after going through the wall.