ventless gas fireplace - figuring size needed

have a converted garage attatched to house so it is now a family room, purchased a ventless propane fireplace to use as a supplement heat source on cold winter days or for ambience when in room, room currently is heated by hydronic baseboard 2 walls, room dimensions are 20x12 with vaulted cieling of 15', no door on room open to entrance area and leads into kitchen and living room and dining room , no doors open layout . figuring approx 2880 cf of space in family room, approx 7880 cf total with combined rooms ( small cape w/ bedroom upstairs approx 1700 sf living space), heat home with pellet stove located in living room. is the size of the vented gas fireplace of 26,000 btu sufficient or overkill ?

thanks for answers on fireplace, we had purchased the ventless fireplace on sale last year and redid the room into a gameroom, probably won't use fireplace that often, only for ambience on occasion while in room,looking for an external regulator for the propane tank, requires a regulator to reduce incoming gas pressure to between 11 -14" wc, also the insert requires an 3/8" inlet connection to pressure regulator, is this a similar regulator like on a gras grill, fireplace is only 26,000 btu's.have been looking on internet for regulators, little confused as to what size to purchase. any help on this would be greatly appreciated. thanks - ken

not sure of mfg, believe it to be procom, bought at lowes, unit is 26,000 btu item # 030334 vent-free gas fireplace insert, model # ssfbd28t