Ocurp
Start a project

Thermal Bridge

Layer-by-layer wall transmittance, the linear thermal bridge value and whether the internal surface will condense.

ScienceThermalU-ValuePsiCondensation
Open now All tools
Thermal Bridge screenshot

A wall build-up, layer by layer. Each layer contributes R = d/lambda, the surface films add R_si and R_se, and U is one over the total. The linear transmittance PSI = f R_si U says how much extra heat the bridging element carries, and the page checks whether the internal surface drops below the dew point of the room - which is the part that actually damages the wall.

Build-up, inside face outward
U-value
Linear transmittance
Resistance, layer by layer
Surface temperature and condensation
A surface sweats when its temperature drops below the dew point of the room air. Dew point here comes from the Magnus formula g = ln(RH/100) + a T/(b + T), Td = b g/(a - g), with a = 17.62 and b = 243.12, valid over water between about -45 and 60 C. The surface drop is f R_si U (Ti - Te), and f is what decides everything: with the usual 0.03 for scattered fasteners a well-built wall loses a couple of hundredths of a kelvin and cannot possibly reach dew point. Push f towards 1, as it goes for an uninsulated steel or stainless element crossing the envelope, and the same wall goes cold enough to drip. That is what a thermal bridge is, and why the flag is worth having.
Read-out




  

  


  




More tools
Science
Molecule Converter
Mass to moles to STP volume for any compound, plus M, mM, mol/L, g/L, mg/mL and ppm, with the molar mass table shown.
Science
Doppler Shift Calculator
Acoustic Doppler for a moving source and observer, and the relativistic longitudinal factor for light, kept strictly apart.
Science
Blackbody Radiation
Wien's peak wavelength and the Stefan-Boltzmann flux, with the luminosity of a star at the radius you type.
Science
Buoyancy Calculator
Archimedes for any object in any fluid: buoyant force, apparent weight and a float or sink verdict from the densities.
Data & code
String Case Converter
UPPER, lower, Title, camel, snake and kebab in one pass.
Data & code
Character & Word Counter
Words, characters, lines, reading time as you type.
Data & code
UUID Generator
Bulk v4 UUIDs from crypto.randomUUID, one click to copy.
Data & code
Hash Generator
SHA-256, SHA-384 and SHA-512 via the Web Crypto API.