Updating attic/roof deck insulation
Good day all,
I have an older home (circa 1905) remodeled and expanded in the 1990’s. During the remodel the previous owner finished the attic and added mechanicals. They insulated the roof deck underneath with fiberglass insulation and the floor of the upper now attic with blow in insulation. Not sure what the r value is but not good. They also did not insulate the duct work which runs around the outside of the living space in the eaves.
I would like to increase the insulation in the attic to increase the efficiency of the home. I will of course be insulating the exposed ductwork to remedy the lack there of and hopefully regain some of the heat/cold that is likely being lost. The more complicated part is the roof deck which I want to insulate. I want to use rock wool insulation between the rafters with a minimum of R23 and 2 inch polyiso or similar over that to prevent thermal bridging. The spaces that need to be insulated are not vented from what I can tell as there are no external soffit vents. As this is essentially a conditioned space I feel like I need to air seal and insulate as best as possible the roof to the interior as opposed to the attic to the living space. Are there any further considerations that I should account for in this project.
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