Floor Construction Templates

Floor Type 1: Wood-Frame Floor Over Unconditioned Space

Typical raised floor over crawlspace or garage

Layer	Material	Imperial Thickness	Metric Thickness	Thermal Conductivity	Thermal Resistance
Interior	Hardwood flooring	3/4"	19 mm	k = 0.080 Btu/(hr·ft·°F)<br>λ = 0.138 W/(m·K)	R-0.94 (RSI-0.16)
Subfloor	OSB or plywood	3/4"	19 mm	k = 0.077 Btu/(hr·ft·°F)<br>λ = 0.133 W/(m·K)	R-0.93 (RSI-0.16)
Structure	Floor joists (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	9-1/2"	241 mm	k = 0.027 Btu/(hr·ft·°F)<br>λ = 0.047 W/(m·K)	R-30 (RSI-5.3)
Air barrier/vapor	Rigid board or membrane (Class III)	-	-	-	-
Exterior	Ventilated crawlspace below	-	-	-	-

Total Assembly: R-30 hr·ft²·°F/Btu (RSI-5.3 m²·K/W)

Notes: Insulation goes between joists with the vapor control facing up toward conditioned space. Hold it tight to the subfloor or you'll get air washing through it. The crawlspace below should be vented (old school) or closed and conditioned (new school).

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Floor Type 2: Slab-on-Grade with Perimeter Insulation

Ground-supported concrete slab

Layer	Material	Imperial Thickness	Metric Thickness	Thermal Conductivity	Thermal Resistance
Interior	Finished flooring (tile, etc.)	Variable	Variable	Variable	Variable
Slab	Reinforced concrete	4"	100 mm	k = 0.90 Btu/(hr·ft·°F)<br>λ = 1.56 W/(m·K)	R-0.5 (RSI-0.09)
Poly vapor barrier	Polyethylene (Class I)	6 mil	0.15 mm	-	-
Sub-slab insulation	XPS rigid foam	2"	50 mm	k = 0.020 Btu/(hr·ft·°F)<br>λ = 0.035 W/(m·K)	R-10 (RSI-1.76)
Capillary break	Crushed stone	4"	100 mm	Variable	Negligible
Perimeter insulation	XPS rigid foam (vertical)	2" × 24" deep	50 × 600 mm	k = 0.020 Btu/(hr·ft·°F)<br>λ = 0.035 W/(m·K)	R-10 (RSI-1.76)
Below grade	Compacted soil	-	-	-	-

Total Assembly: R-10 sub-slab + R-10 perimeter (RSI-1.76 + RSI-1.76)

Notes: Most heat loss from slabs happens at the perimeter, not through the center. That's why the vertical insulation at the edge matters more than you'd think. The poly goes under the slab to stop moisture vapor, not between insulation layers where it creates condensation problems.

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Floor Type 3: Radiant Heat Slab

Hydronic in-floor heating

Layer	Material	Imperial Thickness	Metric Thickness	Thermal Conductivity	Thermal Resistance
Interior	Tile or engineered hardwood	1/2"	13 mm	Variable	Minimal (conductive)
Topping slab	Lightweight concrete or gypcrete	1-1/2"	38 mm	k = 0.90 Btu/(hr·ft·°F)<br>λ = 1.56 W/(m·K)	R-0.19 (RSI-0.03)
Tubing	PEX tubing (embedded)	1/2" dia	13 mm dia	-	-
Structural slab	Reinforced concrete	4"	100 mm	k = 0.90 Btu/(hr·ft·°F)<br>λ = 1.56 W/(m·K)	R-0.5 (RSI-0.09)
Poly vapor barrier	Polyethylene (Class I)	6 mil	0.15 mm	-	-
Sub-slab insulation	XPS rigid foam	3"	75 mm	k = 0.020 Btu/(hr·ft·°F)<br>λ = 0.035 W/(m·K)	R-15 (RSI-2.64)
Capillary break	Crushed stone	4"	100 mm	Variable	Negligible

Total Assembly: R-15 sub-slab (RSI-2.64)

Notes: You want the heat going up, not down, so the sub-slab insulation is critical. The topping slab provides thermal mass and protects the tubing. Don't use high-R-value flooring over radiant or you'll defeat the whole point.

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Floor Type 4: Suspended Concrete Slab

Post-tensioned or reinforced concrete floor

Layer	Material	Imperial Thickness	Metric Thickness	Thermal Conductivity	Thermal Resistance
Interior	Finished flooring (carpet, tile)	Variable	Variable	Variable	Variable
Structural slab	Post-tensioned concrete	8"	200 mm	k = 0.90 Btu/(hr·ft·°F)<br>λ = 1.56 W/(m·K)	R-1.0 (RSI-0.18)
Below	Conditioned space or parking	-	-	-	-

Total Assembly: R-1.0 hr·ft²·°F/Btu (RSI-0.18 m²·K/W)

Notes: This is a thermal boundary only if there's unconditioned space below, which is rare in multi-story buildings. Usually both sides are conditioned so thermal performance isn't the concern. Sound transmission is, but that's a different conversation.

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Floor Type 5: Raised Access Floor

Commercial computer room or office floor

Layer	Material	Imperial Thickness	Metric Thickness	Thermal Conductivity	Thermal Resistance
Interior	Carpet tile or stone	Variable	Variable	Variable	Variable
Floor panels	Steel or aluminum panels	1-1/4"	32 mm	k = 314 Btu/(hr·ft·°F)<br>λ = 543.5 W/(m·K)	Negligible
Air plenum	Adjustable pedestals (6"-24")	12"	305 mm	-	R-1.5 (RSI-0.26)
Structural slab	Concrete slab	6"	152 mm	k = 0.90 Btu/(hr·ft·°F)<br>λ = 1.56 W/(m·K)	R-0.75 (RSI-0.13)

Total Assembly: R-2.25 hr·ft²·°F/Btu (RSI-0.40 m²·K/W)

Notes: The plenum is for cabling and HVAC distribution, not insulation. You access it by lifting panels, which means the thermal boundary is really at the structural slab below. The air space provides minimal R-value but excellent cable management.

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Floor Type 6: Timber Frame Floor

Heavy timber construction

Layer	Material	Imperial Thickness	Metric Thickness	Thermal Conductivity	Thermal Resistance
Interior	Tongue & groove planking	1-1/2"	38 mm	k = 0.080 Btu/(hr·ft·°F)<br>λ = 0.138 W/(m·K)	R-1.9 (RSI-0.33)
Structure	Timber beams (48" OC)	10" × 12"	254 × 305 mm	k = 0.080 Btu/(hr·ft·°F)<br>λ = 0.138 W/(m·K)	R-12.5 (RSI-2.2)
Insulation (between beams)	Rigid mineral wool	10"	254 mm	k = 0.025 Btu/(hr·ft·°F)<br>λ = 0.043 W/(m·K)	R-40 (RSI-7.0)
Air barrier	Vapor-intelligent membrane (Variable)	-	-	-	-
Below	Exposed timber ceiling or conditioned space	-	-	-	-

Total Assembly: R-40 hr·ft²·°F/Btu (RSI-7.0 m²·K/W)

Notes: Heavy timber is exposed for aesthetic and structural reasons, which means insulation goes between beams. The timber itself provides some R-value but creates thermal bridging. Trade-off for the look.

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Floor Type 7: Insulated Concrete Form (ICF) Floor

Foam form stays in place as insulation

Layer	Material	Imperial Thickness	Metric Thickness	Thermal Conductivity	Thermal Resistance
Interior	Finished flooring	Variable	Variable	Variable	Variable
Top insulation	EPS foam	2"	50 mm	k = 0.024 Btu/(hr·ft·°F)<br>λ = 0.041 W/(m·K)	R-8 (RSI-1.4)
Structural slab	Reinforced concrete	6"	152 mm	k = 0.90 Btu/(hr·ft·°F)<br>λ = 1.56 W/(m·K)	R-0.75 (RSI-0.13)
Bottom insulation	EPS foam	2"	50 mm	k = 0.024 Btu/(hr·ft·°F)<br>λ = 0.041 W/(m·K)	R-8 (RSI-1.4)
Ceiling finish	Gypsum or exposed foam	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-17.2 hr·ft²·°F/Btu (RSI-3.0 m²·K/W)

Notes: Same concept as ICF walls but horizontal. The foam formwork remains as permanent insulation on both sides of the concrete. Sound transmission through the concrete is still an issue despite the insulation.

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Floor Type 8: Insulated Above Parking Garage

Separation between unconditioned parking and conditioned space

Layer	Material	Imperial Thickness	Metric Thickness	Thermal Conductivity	Thermal Resistance
Interior	Hardwood or tile	3/4"	19 mm	Variable	Variable
Subfloor	Concrete topping	2"	50 mm	k = 0.90 Btu/(hr·ft·°F)<br>λ = 1.56 W/(m·K)	R-0.25 (RSI-0.04)
Insulation	Rigid mineral wool or XPS	3"	75 mm	k = 0.025 Btu/(hr·ft·°F)<br>λ = 0.043 W/(m·K)	R-12 (RSI-2.1)
Waterproofing	Membrane	-	-	-	-
Structural slab	Post-tensioned concrete	8"	200 mm	k = 0.90 Btu/(hr·ft·°F)<br>λ = 1.56 W/(m·K)	R-1.0 (RSI-0.18)
Below	Parking garage (unconditioned)	-	-	-	-

Total Assembly: R-13.25 hr·ft²·°F/Btu (RSI-2.3 m²·K/W)

Notes: The waterproofing membrane protects the structure from parking garage moisture and chemicals. Insulation goes above it to stay dry and effective. Getting the drainage right matters more than you'd think, because pooling water finds every weakness in the membrane.