Vault ceiling after switching attic from vented to unvented?
In the upstairs portion of our 1949 Massachusetts Cape, the “walls” are roof with 45 degree pitch. There are gables at each end, with a vent near the peak of each gable. There is an unfinished attic, accessible only if I move the 18×22 inch lid in the ceiling of my bedroom closet and climb up there with my step ladder.
From the flat ceiling of each bedroom to the roof’s ridge, there are only four feet (no floor coverings in attic; just bare joists). The portion of roof which envelopes each upstairs bedroom, and also each kneewall, is insulated with 5 inches rockwool batt.
Inside the attic, there is no insulation in rafter bays nor gable walls. We used to have 14 inches of cellulose on attic floor, but recently I discarded nearly all of it (still have a bit more to discard in the next week or so). I am going to have an insulation contractor spray densepack fiberglass (John Manville Spider) into the rafter bays and gable walls of attic. Manufacturer says this product needs no strapping or netting and “breathes” to the inside.
I am going to either switch my gable vents for fixed windows in the same size, or close up those openings entirely. I am also going to undergo reroof. Between sheathing and new roof covering, there will be polylefin barrier plus several layers of polyiso, staggered and taped at seams, for a total of 6 inches.
I want the bedrooms to have cathedral style ceiling instead of flat, so I am thinking to remove the ceiling that separates each bedroom from the attic above. I will consult a structural engineer to ask if it is safe to remove attic floor joists. I think the only structural function of these is to support the attic floor (which I am dying to get rid of!), but I could be wrong. I cannot see how they could be supporting the roof, since the eaves are at the floor of each bedroom, not the floor of attic…?
has anyone on this forum ever switched attic from vented to unvented, insulated roof outside sheating, and then removed attic floor to make cathedral ceilings?
I may keep part of my attic and will make sure that whatever portion I keep has access through the hatch in the closet. Or I may give the entire upstairs cathedral ceilings.
Who has done this, and what advice have you, if any? Thanks
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