It can, especially if the conversion creates a true bedroom, and comparable sales should make the final call. An added bedroom tends to add value. A four-bedroom home often sells for more than a three-bedroom of the same square footage, because buyers shop by bedroom count as much as by size. To count as a bedroom, though, the space usually needs to meet local requirements like a closet and proper egress, so confirm what your area requires before you build. The questions that drive the answer: how usable is the loft as an enclosed room, does closing it in create an awkward floor plan or block light, and have owners of similar homes in your area done the same conversion and seen it reflected in their sale prices. The risk is spending on a conversion that makes the layout feel cramped, or that buyers in your market actually prefer left open as loft space. The best check is comps. Have a local agent pull recent sales of similar homes both with and without the conversion, and let the price difference tell you whether the work is likely to return what you put into it.