New member here trying to figure out what I need to do for my wood stove install. I pulled out an old 1980s metal prefab fireplace which has and exterior alcove for the double walled insulated pipe. I am planning to install a Vermont Casting Dutchwest 246 in the alcove and I don't have a ton of space to do so. The manual tells me I can do 18" on side walls with "protected walls" and a heat shield. What are considered protected walls? Based on this website https://todayshomeowner.com/fireplace/guides/wood-burning-stoves-wall-protection/ you can reduce your spacing by 67% by using the heat shield on wall method. Any help would be appreciated!