Roof Construction Templates

Roof Type 1: Vented Attic with Asphalt Shingles

Most common residential roof system in North America

Layer	Material	Imperial Thickness	Metric Thickness	Thermal Conductivity	Thermal Resistance
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.

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Roof Type 2: Cathedral Ceiling with Fiberglass Batts

Vaulted ceiling with limited depth for insulation

Layer	Material	Imperial Thickness	Metric Thickness	Thermal Conductivity	Thermal Resistance
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.

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Roof Type 3: Unvented Cathedral with Spray Foam

High-performance cathedral ceiling without ventilation

Layer	Material	Imperial Thickness	Metric Thickness	Thermal Conductivity	Thermal Resistance
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.

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Roof Type 4: Flat/Low-Slope EPDM Membrane

Commercial rubber membrane roof

Layer	Material	Imperial Thickness	Metric Thickness	Thermal Conductivity	Thermal Resistance
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.

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Roof Type 5: Modified Bitumen with Ballast

Commercial torch-down or cold-applied membrane

Layer	Material	Imperial Thickness	Metric Thickness	Thermal Conductivity	Thermal Resistance
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.

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Roof Type 6: Standing Seam Metal Roof

Commercial or residential metal roofing system

Layer	Material	Imperial Thickness	Metric Thickness	Thermal Conductivity	Thermal Resistance
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.

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Roof Type 7: Green Roof (Extensive)

Vegetated roof assembly

Layer	Material	Imperial Thickness	Metric Thickness	Thermal Conductivity	Thermal Resistance
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.

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Roof Type 8: SIP Roof Panel

Structural insulated panel roof system

Layer	Material	Imperial Thickness	Metric Thickness	Thermal Conductivity	Thermal Resistance
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.