| Material Thermal Properties |
| Aluminum alloy thermal conductivity | Approximately 205 | W/m·K | Aluminum transfers heat rapidly. This is useful for heat dissipation but can create a thermal bridge when the frame is exposed to both warmer and cooler areas. |
| Thermal resistance of a 1 mm aluminum layer | Approximately 0.0000049 | m²·K/W | Calculated as R = thickness ÷ conductivity. A thin aluminum sheet alone provides very little insulation. |
| Low-conductivity insulation material | Approximately 0.020–0.040 | W/m·K | Common rigid insulation materials can provide far greater resistance than solid aluminum at the same thickness and may be used inside a composite door system. |
| Wood, depending on species and moisture | Approximately 0.12–0.20 | W/m·K | Wood is naturally less conductive than aluminum, although its thermal performance varies with density and moisture content. |
| Glass, typical soda-lime glass | Approximately 1.0 | W/m·K | Glass conducts much less heat than aluminum but still requires suitable glazing design to achieve a low whole-door U-value. |
| Door-System Thermal Performance |
| Uninsulated aluminum door or frame | Approximately 5.0–7.0 | W/m²·K | High heat transfer is likely because the metal forms a continuous conductive path. This construction is generally unsuitable where strong temperature separation is required. |
| Thermally broken aluminum door system | Approximately 1.5–3.0 | W/m²·K | A polyamide or other low-conductivity separator interrupts the metal path. The exact result depends on frame geometry, panel design, glazing, seals, and installation. |
| Insulated aluminum door leaf with continuous thermal break | Approximately 1.2–2.5 | W/m²·K | A suitable option when an aluminum appearance and durable surface are desired without relying on a solid aluminum panel for insulation. |
| Solid wood interior door | Approximately 1.5–2.5 | W/m²·K | Provides moderate thermal resistance, but performance depends on thickness, joints, moisture, and the surrounding frame. |
| Selection Checks |
| Thermal-break material thickness | Commonly several millimeters or more | mm | A wider and better-positioned thermal break generally reduces conductive heat flow, but the complete frame profile must be evaluated rather than the insert alone. |
| Door perimeter air sealing | Continuous compression seal recommended | — | Air leakage can reduce practical thermal performance even when the aluminum profile has a good calculated U-value. |
| Whole-door U-value | Use the tested or calculated value for the complete assembly | W/m²·K | U-value includes the frame, leaf, glazing, edge effects, hardware zones, and seals. It is more useful for comparison than aluminum conductivity alone. |
| Temperature difference across the door | Use the project design condition | K or °C | Heat flow increases as the temperature difference increases. Interior doors between similar-temperature rooms may need less thermal insulation than doors separating conditioned and unconditioned spaces. |
| Recommended decision rule | Prefer a thermally broken, insulated assembly when temperature control matters | — | Do not select an all-aluminum door based only on its material strength or appearance. Confirm the complete door U-value, thermal-break design, glazing specification, and air-sealing details. |
| Note: Conductivity values are representative engineering values and may vary with alloy, temper, density, moisture, temperature, and test method. Whole-door U-values are indicative ranges only; the manufacturer’s tested or calculated performance for the complete installed assembly should be used for final selection. |