Yes, a direct vent gas fireplace can be put anywhere in the house if the vent lengths and turns meets the rules of the manufacturer which are shown in the form of charts & diagrams in the installation instructions. It can vent horizontally to an outside wall or vertically through the roof within those rules. The roof termination would be an exposed metal pipe. Fresh/combustion air is drawn into the outer wall of the vent and the center pipe acts as the exhaust for combustion byproducts. A B-vent gas fireplace can only vent to the roof and draws combustion air from the room (or through a separate outside air duct). It can have a glass face or bi-fold doors. Either unit might have heat recirculating louvers or not. If you find the roof termination unattractive you can add a fake masonry or wood surround. Roof leaks shouldn't be an issue if the roofer knows how to flash a roof penetration. Be sure to use Ice & Water Shield self-adhering flexible flashing in addition to the factory metal flashing. Click on one of the direct vent gas fireplace installation manuals and see if the vent tables will work for your installation. It's a lot of design work if the vent travels horizontally and vertically. Here is a link that might be useful: installation manuals

You only can run 20' horizontal which is the problem. We are actually above ground (full walkout basement) but if we run to the side we vent right outside french doors and onto a porch which has a masonry patio above. There is a box bay for the guest bedroom immediately to the side so we can't go there. We are just a little too far away to run straight back over the guest bedroom because of 6" stud walls and 3" or so of brick . . . My builder is getting conflicting reports from fireplace salespeople about whether a b vent will work. The Isokern folks say theirs will, but the fireplace store says all the ones we have found (which frankly seem to have similar venting requirements to the isokern but just cost less) won't work. The isokern salesperson is saying something about how their system has less heat or something? I can't find anything about that and frankly it concerns me because the other fireplace store's technical guru is finding problems with the b vent installation . . .

I represented Rinnai in its largest US heating market, New England, for 20 yrs. I've trained thousands of dealers/techs on install & service on the Energysaver units. As well, I sold over 180,000 units. Since '91 when they were introduced I've heated my homes, garage and basement with them. Your heating contractor is wrong. It is an outstanding unit for basements. One of the things I like the best about the basement applications is that you are separating the upstairs heating from the basement. I would not want to be tying the basement air to be drawn and mixed into the air going to my girls rooms. I just don't think it is a good idea. Radon and/or possible negative pressure issues in the basement space...it is just not good to pump basement air into the house. Unless you have a walk out basement with exterior walls exposed down to the footing I strongly question being over 40kbtu in 700 sq ft. Personally, in a normal basement ( sub-grade) for 700 sq ft I'd select the EX22. I heated 750 sq ft in my first floor in MA with a 22 very very comfortably. It was an open floor but the 22 did a great job. The 38 will certainly do the job, but it will almost certainly be oversized...substantially. Heat loss is based up delta T, difference in temperature. You will have some of the wall against outside air temps, but as you get to ground level and below the delta T is reduced and therefore so is the heat loss. Again, I have probably 10-15,000 units in the field in basements and I took trouble calls gladly...because there were so few. It is a great product and you will be very comfortable with the 22 or the 38. Oh, and one of the things I liked about the Rinnai in the basement was that after I ran it for a while it would heat the basement ceiling/first floor. It acted like a radiant heater for that floor. It changed the comfort characteristic of the first floor area. Happy Heating!

oh oh oh....sounds a lot like my posts of 2012 doesn't it! I can't believe my system is 2 years old. The choices can make your head spin. I had a similar dilemma with my hwh. I eventually chose tankless and since we have a portable generator I don't worry about the power issues (which you will also have with a power vent). Have to say I LOVE the tankless. Sometimes we just seem to need a lot of hot water, with 4 adults in the house. I have a soaker tub that I love and when it's cold it is delightful to fill it and not worry about who might come home and complain I used all the hot water. I think they ripped me about $4k for that puppy. Perhaps you can sway them into a tankless for the price they quoted you. It is the slow season. I used a company starting with an H,here in south jersey, and I got them to drop about $1500 from the price they had quoted in June by waiting until this time of year. The other company would not budge. My oop was $2k, plus the 0% financed amount. I found the 0% to be very attractive as well so as not to spend cash that could be invested. I sometimes wish I'd gotten the next level up in my furnace, to variable speed from multi speed, because I had humidity issues the first summer. I think that was solved by choosing the correct speed setting as this year has been perfect and my heating has been fine as well, I did get 2-stage heat and ac. I just came up against my price limit and decided the luxury of the tankless was how I wanted to go (rather than up the heater another level) The guys here got VERY tired of me (sometimes rightly so!) Perhaps you can find the old threads (novels almost!) that I posted here about the NJ CLEAN ENERGY program. By the way, I did do some reading online and it can be true that if your house is well sealed that a conventional heater may not draft properly causing a risk of carbon monoxide buildup, which is why they talk you into a power vent or tankless. Good luck. Try not to overthink or get too wrapped up in it. Accept that you will save SOME $, but the contractor will get at least half your rebate $ in mark ups. Are you getting insulation added? I think that was a good thing that I wouldn't have done otherwise.