# 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)\
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)\
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)\
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)\
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).
***
### 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)\
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)\
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)\
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.
***
### 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)\
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)\
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)\
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.
***
### 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)\
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.
***
### 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)\
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)\
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.
***
### 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)\
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)\
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)\
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.
***
### 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)\
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)\
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)\
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)\
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.
***
### 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)\
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)\
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)\
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.