In a zone 6 remodel of a 1-bed heavily shaded 1988-vintage tree house on steel columns and 24x24 guesthouse over garage, walls change from concrete/block under and above ground to 2x6. Concrete/block exterior lines up with 2x6 sheathing exterior. Existing 2x6 walls have 6” fiberglass insul. and 1/2" plywood sheathing, but new 2x6 walls can be done differently. Please let me know the layers above/below grade and roof layers you suggest that would be cost-effective and provide great insulation without condensation problems. Planned wall finish is Dryvit (e.g. Outsulation X) or flat Alu/Zinc panel rainscreen over 2” XPS or polyiso/XPS above/below grade. New windows will be wall to wall triple glazed leaving room for only ¾” thermal break on sides of many steel columns in order to line up with 2x6 interior walls that encase steel columns, but window frames will be overinsulated. Guesthouse over garage roof. Plan is to convert to low slope PMR with 15” +/- ceiling to top of ballast - 5/8” sheetrock ceiling, ½” polyiso, 6” steel beams (spray foam between?), steel deck, spray-on membrane, sheet membranes, 2”+ XPS, protection layer, 3” chipped slate ballast. A 6” parapet will confine insulation and ballast, assuming we can get away with a shallow roof structure with insulation between steel beams. Guesthouse over garage wall. Existing uninsulated, partially buried block forms a moisture-laden garage that rusts metal. Plan to add 2” XPS up block and 2x6 sheathing with insulation in stud cavity. This could be part of Outsulation X structure or other 2” XPS/polyiso insulated finish. Tree house roof. Plan to replace with metal roof (Zinc or steel) over 2” XPS over existing plywood sheathing on 2x10s with 9” fiberglass over ceiling. HVAC equipment in a 15x15 attic is being relocated under the tree house so heavy insulation above unfinished attic sheetrock (polluted by mice and squirrels) can be removed. Without HVAC and wtr htr in attic we could shift 7’ attic ceiling up to 2x10s and use the room, e.g., as an office. Tree house wall. A profile of the existing structure the new wall has to enclose consists of 5/8” nut (after sawing off bolt tip), ¼” steel plate, 5 1/8” glulam, ¼” steel plate, ½” bolt head (i.e. 6 ¾” thick nut to bolt). The ½” bolt head projects ¼” outside existing 2x6 plywood sheathing so we can shave the XPS, so the new wall can be 6.5” thick before applying sheetrock and XPS. New stemwall exterior will align with new and existing sheathing exteriors. We add the Outsulation X or other 2” XPS/polyiso insulated finish to provide R10+ over the currently exposed steel. If we use a metal panel we can attach XPS using ½” channel for drainage. Either way, there is a ½” gap from XPS to glulam and ¼” gap to steel plate so should we coat the steel plate or the glulam? We can protect the 2” xps underground from rodents with ½” fiberglass or ? A ½” deep metal strip or ½” polyiso applied to inside of 6” stud or stem wall will line up with 5/8” nut before we apply 5/8 sheetrock, but is 1/2" XPS OK with 2” XPS/polyiso on exterior and whatever we have in stud cavity? Also, not sure what stud cavity insulation to use that would be most cost effective and avoid condensation given the 2” exterior XPS/polyiso. Planned for only 1” +/- inside stemwall to avoid squeezing narrow master bath.