Roof System: R-100
Energy-Heel Roof Trusses
We installed 30-inch deep raised-heel roof trusses, allowing the truss cavities to be filled with dense-packed cellulose insulation at R-100.
Roof Sheathing & Underlayment Membrane
We sheathed the roof exterior with 5/8-inch plywood and covered this with a combination of Ice and Water Shield (a waterproof membrane placed at the bottom and edges of the roof plane) and breathable 30-pound felt, which allows moisture to pass through the roof assembly.
Roof Ventilation Channel
Over this roof deck, 1x4 cross-laminated strapping provides a ventilation channel for the roof system and an attachment for the standing seam steel roof. It also created a convenient ladder system for the roof installers.
1x4 cross-laminated strapping provides roof ventilation.
The roof’s cross-laminated strapping for the ventilation channel provides a handy ladder for the roof installers.
Galvanized Standing Seam Roof
We chose a galvanized standing seam roof with a Galvilum protective coating for its longevity, its recyclability and its aesthetic. It should last at least 50 years.
The west elevation of the galvanized standing seam roof.
Dense-Packed Cellulose Insulation
Covering the interior side of the extra deep trusses, 0.5-inch OSB creates an enclosed cavity for 30 inches of dense-packed cellulose insulation, giving the roof an R-value of 100.
Sealing All Joints
We taped all the OSB seams and sealed the juncture between the second-level plywood subfloor and the interior OSB ceiling with OSI Quad polyurethane caulk and 3M flashing tape.
Caulking between interior roof and second-floor plywood.
Mechanical Chase
Over the OSB, horizontal 2x3s provide an 1.5-inch electrical chase in the second-floor ceiling, which houses the shallow 1.5-inch deep electrical boxes. Half-inch drywall finished the ceiling.
Second-floor ceiling mechanical chase.
Installing the last interior roof system layer: 1/2-inch drywall.
Roof System Layers, Inside to Outside
ABOUT R-100:
1/2-inch drywall
1.5-inch electrical chase
1/2-inch OSB, taped with 3M flashing tape
30-inch deep energy-heel roof trusses, filled with dense-packed cellulose
5/8-inch plywood sheathing
Combination of Ice and Water Shield and 30-pound felt
1x4-inch cross strapping, to create a ventilation channel
Standing seam Galvalume metal roof