Calculate thermal transmittance from layered assemblies and heat flow. Test insulation decisions with clear metrics. Review resistance, conductance, losses, and exported summaries in seconds.
| Assembly | Total R (m²·K/W) | U-Factor (W/m²·K) | Area (m²) | ΔT | Heat Flow (W) |
|---|---|---|---|---|---|
| Insulated wall | 4.2000 | 0.2381 | 25 | 18 | 107.14 |
| Double glazed unit | 0.5556 | 1.8000 | 8 | 20 | 288.00 |
| Roof panel | 5.0000 | 0.2000 | 40 | 16 | 128.00 |
This table is illustrative. Your project values may differ.
Layer resistance: R = d / k
d is layer thickness in meters. k is thermal conductivity in W/m·K.
Total resistance: Rtotal = Rsi + ΣRlayers + Rse + Rextra
U-factor: U = 1 / Rtotal
Heat flow: Q = U × A × ΔT
Measured mode: U = Q / (A × ΔT)
These formulas help compare walls, roofs, windows, and insulated panels. Lower U-factor means better thermal performance. Higher total resistance means slower heat transfer through the assembly.
A U-factor calculator helps you measure how quickly heat moves through a building element. It is useful for walls, roofs, doors, skylights, and glazed units. Lower values mean better insulation. Higher values mean faster heat loss. This makes U-factor a practical performance metric for energy analysis and thermal design.
This calculator supports two common approaches. The first method uses layer thickness and conductivity. It builds resistance one layer at a time. The second method uses measured heat flow, area, and temperature difference. That method is useful when you already know how much heat passes through the assembly.
Resistance is the inverse of conductance. Each material adds thermal resistance based on its thickness and conductivity. Surface films also matter. Interior and exterior films change real performance. When all resistances are added, the calculator converts the total into a U-factor. This gives a cleaner view of whole-assembly heat transfer.
You can compare insulation options, glazing builds, retrofits, and envelope upgrades. The result section also shows conductance and estimated heat flow. That helps you understand operating impact, not just theory. Designers, estimators, students, and property managers can all use the output to make quicker decisions.
The example table gives a reference point. The formula section explains each step. The export buttons support reporting and record keeping. Use the layered method during design. Use the measured method during audits or site checks. Together, these options make the calculator practical for planning, verification, and thermal performance review.
U-factor measures heat transfer through a building element. It shows how much heat passes through one square meter for each degree of temperature difference.
Yes. A lower U-factor means the assembly resists heat flow better. That usually improves insulation performance and energy efficiency.
The main result uses W/m²·K. It also shows an IP conversion in Btu/h·ft²·°F for easier comparison with other references.
Inside and outside surface films affect real thermal behavior. Including them gives a more realistic total resistance for the assembly.
Yes. You can use it for windows, walls, roofs, insulated panels, and other envelope elements if you know the needed inputs.
Use measured heat flow mode. Enter area, temperature difference, and heat flow. The calculator will derive the U-factor and equivalent resistance.
Millimeters are common in construction and product sheets. The calculator converts thickness to meters before applying the resistance formula.
Yes. After calculation, you can download the result as CSV or PDF for reports, review, or sharing.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.