In a study of Manhattan sales that appraiser Jonathan Miller made with researchers from NYU’s Furman Center for Real Estate and Urban Policy, apartments with fireplaces cost an average of about 10 percent more than those without. (The difference was 11.4 percent in condos, 9.7 in co-ops.) But the fireplace is “part of a suite of amenities” not easily parsed from other prewar features like high ceilings. Miller estimates that the fireplace itself adds 2 to 5 percent to the price. That’s a fairly wide range, depending majorly on placement: A mantel in the center of the living room is worth a lot more than if it’s in a back bedroom. And if the fireplace doesn’t work, or the flue needs more than a cosmetic touch-up? That cuts the value by half.