Insulating Room In Attic Trusses
I’m constructing a shop building for myself – 44′ x 30′ with a second floor/attic space. The main floor will be heated workshop space with a ceiling hung unit heater. I plan on using the attic space for a woodworking shop, unheated for now.
I am using Room In Attic trusses for the roof construction. The top cords are 7 1/4″ deep. The bottom cords are 11 1/4″ deep. Looking for advice on the best insulation strategy. I want to avoid spray foam due to cost and quality issues. I plan on using rock wool for its fire resistance and higher R-value compared to fiberglass. Should I?:
A). Insulate the ceiling space between the main floor and the attic space with 11 1/2″ of rock wool? Also insulate the 7 1/4″ top cords in the attic space with 5 1/2″ rock wool (leaving an 1 1/2″ ventilation channel above the rock wool to the bottom of the roof sheathing – I’d use Accuvents for this).
B). Fur out the 7 1/4″ top cords to get enough room for the 1 1/2″ ventilation channel and 12″ of rock wool? My plan would be to use metal studs, attached on edge, to the bottom edge of the truss cords. The “C” shape of the metal studs allows for easy attachment to the wooden truss cord. The rock wool will fill the space in the metal stud, helping to eliminate thermal bridging.
C). Your idea :).
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