Operating ranges, flow data, insulation requirements, tubing specs, and design principles — Version 2027.
| Supply Water Temperature | 38°C – 82°C (100°F – 180°F) |
| Design Supply Temperature | 49°C – 60°C (120°F – 140°F) Recommended for typical residential loads |
| Maximum Floor Surface Temp. | 29°C (84°F) |
| Design Delta-T | 10°C – 20°C (18°F – 36°F) |
| Operating Pressure | Max 100 PSI (690 kPa) |
| Test Pressure | 60 PSI minimum, 30 min hold |
| Tubing Type | PEX-A, PEX-B, PEX-C |
| Standard Tubing OD | 1/2" (12.7mm) or 5/8" (15.9mm) |
| Minimum Bend Radius | 8× tubing outside diameter |
| Maximum Circuit Length | Per design — consult layout tool |
| Fitting Requirement | None within fin zone; standard at manifold |
| Gas Condensing Boiler | Fully compatible — optimal at 49–60°C |
| Oil Boiler | Compatible with proper mixing valve |
| Air-Source Heat Pump | Compatible — low supply temps favored |
| Ground-Source Heat Pump | Optimal — matches low supply temp design |
| Solar Thermal | Compatible as supplemental or primary |
| Electric Boiler | Compatible |
| Material | Extruded aluminum alloy |
| Fin Width | To joist bay — standard and custom widths |
| Thermal Conductivity | 205 W/m·K (aluminum) |
| Clip Spacing (typical) | 8" on center — varies by heat load design |
| Tubing Clip Opening | Sized for 1/2" and 5/8" OD PEX |
| Subfloor Contact | Fin presses to subfloor — full-width contact |
| Over conditioned space | R-11 min / R-19 preferred |
| Over vented crawlspace | R-19 min / R-30 preferred |
| Over unheated garage | R-19 min / R-30 preferred |
| Over exterior / cantilever | R-30 min / R-38 preferred |
| Insulation placement | Flush against bottom chord — no air gap |
| Maximum floor covering R-value | R-1.5 (combined covering + pad) |
| Hardwood — solid | Compatible · surface ≤ 27°C (80°F) |
| Engineered wood | Compatible · follow mfr. temp limits |
| Tile / natural stone | Compatible — no restrictions |
| LVP / laminate | Radiant-rated products · ≤ 27°C surface |
| Carpet + pad | Combined R-value ≤ 1.5 recommended |
Ultra-Fin's performance is based on fundamental heat transfer principles applied to the specific geometry of a wood-frame floor assembly.
Aluminum fins conduct heat from the tubing laterally across the subfloor. The fin cross-section and alloy are chosen to maximize lateral heat spreading while minimizing material cost.
The fin must press against the subfloor to minimize contact resistance. Spring-clip tension maintains continuous contact. Air gaps between fin and subfloor significantly reduce output.
Spacing is not arbitrary — it is calculated from the design heat load per square foot, the supply and return temperatures, and the floor assembly thermal resistance. Ultra-Fin provides project-specific spacing specifications.
The target is even floor surface temperature across the entire area. The fin spacing formula is derived to produce ≤3°C variation across the floor surface — eliminating the warm-stripe effect common in staple-up systems.
Lower supply water temperatures improve the efficiency of all hydronic heat sources — especially condensing boilers (which condense more) and heat pumps (higher COP). Ultra-Fin's high-efficiency heat transfer supports lower supply temps for the same comfort output.
The ratio of subfloor thermal resistance to under-system insulation determines how much heat travels upward versus downward. Minimum insulation values are set to ensure at least 85% of heat output moves toward the living space.
Contact Ultra-Fin for project-specific design support, layout drawings, and specification documents.