Thanks for your input, Renovator8. That fireplace has been through a few transitions. It was first an Isokern masonry like fireplace but to save some money we changed it to a b-vent on the plans. Once we placed the house on the lot, it became apparent that the b-vent pipe would be viewable from the street, and would have to be fairly high due to the slope of the roof. The initial hope was to hide the b/vent pipe from view behind the upstairs Isokern chimney, but the house is oriented in a way that it is viewable on approach, even though not seen in the front or back yard. We then changed to an direct vent. The whole reason for the direct vent was to not vent to the roof, so I would like to avoid that. We have a couple of options with the Montebello like running them behind a bookshelf in the dead space and then over a boxed bay bumpout, but the pipe is so big it may make it not feasible. I don't think we have enough rise available to run it over the master bedroom tray ceiling above, unfortunately, because that will vent out the side of a house above the a/c in a very inconspicuous place.

I called _ Napoleon, the restrictor disk is in the fripeplace, and can be used if needed. Well i have another problem, i will post as a new thread.

IMO, go direct vent. The top vent (regular chimney) is just that, a regular chimney pipe - a single pipe carrying combustion products out of the home. When using a regular chimney, the combustion air comes from somewhere else, usually leaky windows, doors, bathroom fans etc. To me that means you lose comfort (it's drafty) in those areas where you're pulling combustion air into the home. And the pipe gets hot so you have to respect the proper firecode installation rules. On the other hand, direct vent chimneys are double-wall pipe. The center pipe carries the hot combustion products out of the home and the surrounding outer pipe brings in the outside air. That cuts down on the drafts at doors and windows, plus the outside of the vent pipe runs cooler, so it should be safer from a fire standpoint (you still install it per the firecode). The safety of direct vent IMO would be higher. I don't think there would be any major difference between installation, cost, appearance of the fireplace, or flexibility between the two options.

Most direct vent fireplaces use something like Duravent 58, which has two concentric pipes. The flue is inside the center 5" pipe and the vent air comes from the space between the 5" pipe the 8" pipe. The wall framing and other flammable materials only have to be 1" away from the outside of the 8" pipe. If you use approved pipe accessories, (wall thimble, floor fire stop, etc.) it will maintain the proper spacing when it goes through walls, roofs, etc. However, spacing for the mantel is different. For example, I think my direct vent fireplace required 13" from the top of the fireplace front to any flammable materials. That means the bottom of the mantel had to be 13" or more higher than the front of the fireplace. Bruce