I recently installed a new asphalt roof on my 1906 modified hip roof in Michigan.  The roof framing is essentially a hip with a section at the front consisting of a ridge intersecting with one of the hip rafters.  That ridge continues forward to the front of the house.  This in effect creates another hip section at the front connected by the ridge.  To one side of that is a long valley where the footwprint of the house jogs in for the entry.  On each of the sides is a mediumish sized dormer.  One is new and one exists for headroom for the stariway.  This space creates a full walk-up attic that was once finished with plaster and lath.  It is a great space that I am aiming to reclaim in the coming years.  It is currently 90% gutted of plaster.  All of this is framed with full 2 x 4’s.  That’s the visual.<!—-><!—-> <!—->

I am looking to take the first step, insulating, to putting that space back to use.  My current plan is to place the insulation in the rafter bays.  The attic has a knee wall around the perimeter.  I would like to continue the insulation down to the eave and keep the space in the knee wall as conditioned and install various built-ins.  The current plan goes a little like this.  <!—-><!—->

1.     Fur down the rafters from eave to the 8-ft high ceiling joists using steel studs screwed to the interior face of the existing rafters.  I might add a thermal break of either rips of foam or, if it’s enough, sill sealer.<!—-><!—->

2.    Seal with a combination of thermoply, foam board, spray foam all rafter bays at the exterior wall.<!—-> <!—->

3.    Install 1.5†poly-iso foam board on the interior of the system with all joint gaps spray foamed and seams taped.<!—-><!—->

4.    Dense pack cellulose insulation from the high point of the rafter bay without baffles creating an unvented roof assembly.<!—-> <!—->

5.    Install gypboard from kneewall up to and across the ceiling joists.  <!—-> <!—->

6.    Seal the few penetrations related to electrical in the ceiling plane.<!—-><!—->

My admission is that I may not have done my research for the proper handling of the moisture created within the house.  If I can effectively keep the moisture from getting into the roof system through the use of the poly-iso layer (or another vapor barrier system) can I go unvented in my climate with dense pack cells?  The design of the roof is difficult enough to vent in its current state.  Spray foam is out of the question at this point due to the high cost.  I considered after determining the high cost going with foam board installed within the rafter bays and filling any gaps with spray foam.  <!—-> <!—->

I’d like some feedback or review of this idea.<!—-> <!—->