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Insulating a conditioned Cape second floor – Cathedral…I think?

meboice58 | Posted in Energy Efficiency and Durability on

Hello all,

I know that this topic has been covered here so many times, but some elements to my house may be different.  The work is being performed on a 1961 Cape with a 9/12 pitch roof.

The tar paper and Life Time 🙂 Shingles were installed ten years ago.  I also ‘shoved’ pink proper vents in between the rafters at the same time from behind the knee walls…the insulation in the roof has mostly collapsed.

We have central air, the basement foundation was exposed to the footings, I added Thoroseal to the outside of the CMU walls, I little trowel on tar, 1″ polystyrene, new footing drains to daylight and about 60 tons of 3/4″ stone.  The basement dry…I add this because I think that a house inhales from the basement…

All basment egress windows and first floor windows/doors are Low e, argon gas filled.

First floor insulation is R15 between 2×4 stud walls

I attached a pdf which is color coded to help see existing and proposed work.
I did not mirror the work on the right side of the image…I was saving time.

I am performing most of the work myself…and have done so.  Only the spray foam company is being hired to spray in closed and open cell.  This space is currently our master bedroom.  

Basically, I am adding full width vents using 1″x1″ and lauan panels glued and nailed to the 1″x1″.

Then 2″ of closed cell, then 2.5″ of open cell, then 1″ polystyrene under the rafters and down the inside of the knee walls.

The knee walls currently have R13 between the studs and another layer of R21 in the unconditioned knee wall space.

The unconditioned knee wall space has 1/2″ plywood floor with R21 sitting on top. The entire 1st floor ceiling is filled with R21

I used core vents in the soffit at the wall face (blue in the diagram).  

We currently have a gable fan that runs in summer…i can feel the air being sucked in from the core vents when standing outside.  But the fan will be removed as I plan to completely fill the space above the collar ties ???

Apologies for the litany, I am trying to be detailed because I would like to avoid doing this twice…which happens often 🙂

This area, which runs the full width of the house, is very cold in winter and very warm in summer.

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