About Thermal Movement Calculator
The thermal movement calculator determines how far facade elements expand and contract with temperature, then sizes the expansion joint and matches a compatible sealant. It is used by facade engineers for curtain walls, cladding panels, and structural glazing, in line with ASTM C1193 and ISO 11600 sealant movement classes.
Select a material from the CTE database, set the element length and temperature range, optionally add structural, seismic, and moisture movement, and the tool returns the total movement and the required joint width with the sealant capacity it consumes.
How It Works
- Pick a material to load its coefficient of thermal expansion (CTE) and set the element length.
- Correct the peak surface temperature for solar gain using the sol-air relationship and the surface absorptance.
- Compute expansion from install to maximum and contraction from install to minimum, then combine with any structural, seismic, and moisture movement.
- Size the joint width from the total movement and the sealant movement capacity, applying a safety factor and a 6 mm minimum.
Worked Example
A 3000 mm aluminium panel (CTE = 23e-6 per K) over a 50 K corrected range moves deltaL = 23e-6 * 3000 * 50 = 3.45 mm. With a +/-25% sealant and a 1.25 safety factor, the joint width is 3.45 / 0.25 * 1.25 = 17.3 mm.
Formulas
- Linear thermal movement
deltaL = CTE * L * deltaT- Surface (sol-air) temperature
T_surface = T_air + (a * I) / h- Joint width sizing
W = (M_total / (C / 100)) * SF
Standards & References
- ASTM C1193
- EN 13830
- ISO 11600
Frequently Asked Questions
How is thermal movement calculated?
Movement equals the coefficient of thermal expansion times the element length times the temperature change (deltaL = CTE * L * deltaT). The tool applies it separately for expansion and contraction about the installation temperature.
Why correct for surface temperature instead of air temperature?
A dark, sun-exposed facade reaches a sol-air temperature well above ambient. The tool adds (absorptance * solar intensity) / surface heat transfer to the air temperature so the movement reflects the real peak surface temperature.
How is the expansion joint width determined?
The total movement is divided by the sealant movement capacity (for example +/-25%) and multiplied by a safety factor, subject to a 6 mm minimum, so the joint and sealant can absorb the movement without failure.
Does the tool consider movement other than thermal?
Yes. You can add structural deflection, seismic drift, and moisture movement, and the tool combines them conservatively with the thermal movement when sizing the joint.