Roof Construction Templates
Roof Type 1: Vented Attic with Asphalt Shingles
Most common residential roof system in North America
Exterior
Asphalt shingles
1/8"
3 mm
k = 0.43 Btu/(hr·ft·°F)<br>λ = 0.74 W/(m·K)
Negligible
Underlayment
Felt or synthetic (Class III)
-
-
-
-
Sheathing
OSB or plywood
1/2"
13 mm
k = 0.077 Btu/(hr·ft·°F)<br>λ = 0.133 W/(m·K)
R-0.6 (RSI-0.11)
Ventilation
Attic space (vented)
Variable
Variable
-
-
Insulation (attic floor)
Blown fiberglass or cellulose
14"
356 mm
k = 0.027 Btu/(hr·ft·°F)<br>λ = 0.047 W/(m·K)
R-49 (RSI-8.6)
Air/vapor control
Ceiling gypsum acts as air barrier
-
-
-
-
Interior
Gypsum drywall
1/2"
13 mm
k = 0.096 Btu/(hr·ft·°F)<br>λ = 0.166 W/(m·K)
R-0.45 (RSI-0.08)
Total Assembly: R-50 hr·ft²·°F/Btu (RSI-8.8 m²·K/W)
Notes: Attic requires minimum 1:150 net free ventilation area (soffit to ridge). Insulation must not block ventilation at eaves. This is the cheapest way to hit code minimums, which is why it's everywhere.
Roof Type 2: Cathedral Ceiling with Fiberglass Batts
Vaulted ceiling with limited depth for insulation
Exterior
Asphalt shingles
1/8"
3 mm
k = 0.43 Btu/(hr·ft·°F)<br>λ = 0.74 W/(m·K)
Negligible
Underlayment
Synthetic roof underlayment (Class III)
-
-
-
-
Sheathing
OSB or plywood
1/2"
13 mm
k = 0.077 Btu/(hr·ft·°F)<br>λ = 0.133 W/(m·K)
R-0.6 (RSI-0.11)
Ventilation
Air space (min. 2")
2"
50 mm
-
R-1.0 (RSI-0.18)
Baffles
Ventilation baffles
-
-
-
-
Structure
Rafters (16" OC)
9-1/2" (2x10)
241 mm
k = 0.080 Btu/(hr·ft·°F)<br>λ = 0.138 W/(m·K)
R-11.9 (RSI-2.09)
Insulation
Fiberglass batt
7-1/2"
190 mm
k = 0.027 Btu/(hr·ft·°F)<br>λ = 0.047 W/(m·K)
R-28 (RSI-4.9)
Air barrier
Vapor-intelligent membrane (Variable)
-
-
-
-
Interior
Gypsum drywall
1/2"
13 mm
k = 0.096 Btu/(hr·ft·°F)<br>λ = 0.166 W/(m·K)
R-0.45 (RSI-0.08)
Total Assembly: R-30 hr·ft²·°F/Btu (RSI-5.3 m²·K/W)
Notes: The 2" ventilation gap eats into your available insulation depth, which is why cathedral ceilings struggle to meet modern energy codes. You're borrowing from thermal performance to prevent ice dams and moisture issues.
Roof Type 3: Unvented Cathedral with Spray Foam
High-performance cathedral ceiling without ventilation
Exterior
Asphalt shingles
1/8"
3 mm
k = 0.43 Btu/(hr·ft·°F)<br>λ = 0.74 W/(m·K)
Negligible
Underlayment
Synthetic roof underlayment (Class III)
-
-
-
-
Sheathing
OSB or plywood
1/2"
13 mm
k = 0.077 Btu/(hr·ft·°F)<br>λ = 0.133 W/(m·K)
R-0.6 (RSI-0.11)
Structure
Rafters (16" OC)
11-1/4" (2x12)
286 mm
k = 0.080 Btu/(hr·ft·°F)<br>λ = 0.138 W/(m·K)
R-14.1 (RSI-2.47)
Insulation
Closed-cell spray foam
11-1/4"
286 mm
k = 0.016 Btu/(hr·ft·°F)<br>λ = 0.028 W/(m·K)
R-67 (RSI-11.8)
Interior
Gypsum drywall
1/2"
13 mm
k = 0.096 Btu/(hr·ft·°F)<br>λ = 0.166 W/(m·K)
R-0.45 (RSI-0.08)
Total Assembly: R-68 hr·ft²·°F/Btu (RSI-12.0 m²·K/W)
Notes: Closed-cell foam acts as its own air barrier and vapor control (Class II). No ventilation required, which gives you the full rafter depth for insulation. Expensive, but effective. Building inspectors may want to see code references the first time you try this.
Roof Type 4: Flat/Low-Slope EPDM Membrane
Commercial rubber membrane roof
Exterior
EPDM rubber membrane
60 mil
1.5 mm
k = 0.13 Btu/(hr·ft·°F)<br>λ = 0.225 W/(m·K)
Negligible
Cover board
Gypsum cover board
1/2"
13 mm
k = 0.096 Btu/(hr·ft·°F)<br>λ = 0.166 W/(m·K)
R-0.45 (RSI-0.08)
Insulation
Polyiso rigid foam
4"
100 mm
k = 0.014 Btu/(hr·ft·°F)<br>λ = 0.024 W/(m·K)
R-24 (RSI-4.2)
Vapor retarder
Self-adhered membrane (Class II)
-
-
-
-
Roof deck
Steel deck
22 ga
0.76 mm
k = 314 Btu/(hr·ft·°F)<br>λ = 543.5 W/(m·K)
Negligible
Structure
Open-web steel joists
Variable
Variable
-
-
Interior
Suspended ceiling or exposed
-
-
-
-
Total Assembly: R-24.5 hr·ft²·°F/Btu (RSI-4.3 m²·K/W)
Notes: The vapor retarder location is critical. Get it wrong and you'll condense moisture at the deck, which steel doesn't appreciate. Tapered insulation creates positive drainage because perfectly flat roofs are a myth.
Roof Type 5: Modified Bitumen with Ballast
Commercial torch-down or cold-applied membrane
Exterior
River stone ballast
3"
75 mm
k = 1.50 Btu/(hr·ft·°F)<br>λ = 2.60 W/(m·K)
R-2.0 (RSI-0.35)
Membrane
Modified bitumen (2-ply)
1/4"
6 mm
k = 0.11 Btu/(hr·ft·°F)<br>λ = 0.19 W/(m·K)
Negligible
Insulation
EPS rigid foam
5"
127 mm
k = 0.024 Btu/(hr·ft·°F)<br>λ = 0.041 W/(m·K)
R-20 (RSI-3.5)
Vapor retarder
Self-adhered membrane (Class II)
-
-
-
-
Roof deck
Concrete deck
6"
152 mm
k = 0.90 Btu/(hr·ft·°F)<br>λ = 1.56 W/(m·K)
R-0.75 (RSI-0.13)
Structure
Concrete structure
Variable
Variable
-
-
Interior
Exposed concrete or ceiling
-
-
-
-
Total Assembly: R-22.8 hr·ft²·°F/Btu (RSI-4.0 m²·K/W)
Notes: Ballast holds the membrane down mechanically instead of adhesive. Makes repairs interesting since you're moving rocks around first. The thermal mass of the concrete deck helps with temperature swings.
Roof Type 6: Standing Seam Metal Roof
Commercial or residential metal roofing system
Exterior
Standing seam metal panels
24 ga
0.61 mm
k = 314 Btu/(hr·ft·°F)<br>λ = 543.5 W/(m·K)
Negligible
Underlayment
Synthetic roof underlayment (Class III)
-
-
-
-
Sheathing
OSB or plywood
5/8"
16 mm
k = 0.077 Btu/(hr·ft·°F)<br>λ = 0.133 W/(m·K)
R-0.75 (RSI-0.13)
Ventilation
Air space (vented)
1-1/2"
38 mm
-
R-1.2 (RSI-0.21)
Structure
Rafters (24" OC)
9-1/2" (2x10)
241 mm
k = 0.080 Btu/(hr·ft·°F)<br>λ = 0.138 W/(m·K)
R-11.9 (RSI-2.09)
Insulation
Closed-cell spray foam
7-1/2"
190 mm
k = 0.016 Btu/(hr·ft·°F)<br>λ = 0.028 W/(m·K)
R-45 (RSI-7.9)
Air barrier
Spray foam acts as air barrier
-
-
-
-
Interior
Gypsum drywall
1/2"
13 mm
k = 0.096 Btu/(hr·ft·°F)<br>λ = 0.166 W/(m·K)
R-0.45 (RSI-0.08)
Total Assembly: R-47 hr·ft²·°F/Btu (RSI-8.3 m²·K/W)
Notes: Metal conducts heat like nobody's business, so the ventilated air space above the sheathing prevents the roof from turning into a radiator. Without it, you're basically heating the neighborhood in summer.
Roof Type 7: Green Roof (Extensive)
Vegetated roof assembly
Vegetation
Sedum or hardy plants
3-6"
75-150 mm
Variable
Variable
Growing medium
Engineered soil mix
4"
100 mm
k = 0.25 Btu/(hr·ft·°F)<br>λ = 0.43 W/(m·K)
R-16 (RSI-2.8)
Filter fabric
Geotextile
-
-
-
-
Drainage layer
Drainage mat
1"
25 mm
-
R-1.0 (RSI-0.18)
Waterproof membrane
EPDM or TPO (root-resistant)
60 mil
1.5 mm
k = 0.13 Btu/(hr·ft·°F)<br>λ = 0.225 W/(m·K)
Negligible
Protection layer
Protection board
1/4"
6 mm
-
-
Insulation
Polyiso rigid foam
3"
75 mm
k = 0.014 Btu/(hr·ft·°F)<br>λ = 0.024 W/(m·K)
R-18 (RSI-3.2)
Vapor retarder
Self-adhered membrane (Class II)
-
-
-
-
Roof deck
Concrete deck
8"
200 mm
k = 0.90 Btu/(hr·ft·°F)<br>λ = 1.56 W/(m·K)
R-1.0 (RSI-0.18)
Total Assembly: R-36 hr·ft²·°F/Btu (RSI-6.3 m²·K/W)
Notes: The growing medium provides thermal mass and variable R-value depending on moisture content. Wet soil insulates poorly but provides evaporative cooling. Your structural engineer will want to know about the saturated weight, which is considerable.
Roof Type 8: SIP Roof Panel
Structural insulated panel roof system
Exterior
Asphalt shingles or metal
1/8"
3 mm
Variable
Negligible
Underlayment
Synthetic roof underlayment (Class III)
-
-
-
-
Outer facing
OSB sheathing
7/16"
11 mm
k = 0.077 Btu/(hr·ft·°F)<br>λ = 0.133 W/(m·K)
R-0.5 (RSI-0.09)
Core
EPS foam insulation
10-1/4"
260 mm
k = 0.024 Btu/(hr·ft·°F)<br>λ = 0.041 W/(m·K)
R-41 (RSI-7.2)
Inner facing
OSB sheathing
7/16"
11 mm
k = 0.077 Btu/(hr·ft·°F)<br>λ = 0.133 W/(m·K)
R-0.5 (RSI-0.09)
Interior
Gypsum drywall or exposed
1/2"
13 mm
k = 0.096 Btu/(hr·ft·°F)<br>λ = 0.166 W/(m·K)
R-0.45 (RSI-0.08)
Total Panel: R-42.5 hr·ft²·°F/Btu (RSI-7.5 m²·K/W)
Notes: Factory-built means quality control is better than field assembly. The panel itself is the structure, so no thermal bridging through rafters. Ridge and valley details require careful engineering because you can't just slap blocking in there.
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