Watch ΨMonkey solve a junction

22-second demo · silent screencast, captions included · the free psi value calculator

Pick a standard SAP junction, change a thickness in the layer list, and watch the Ψ-value and f_Rsi re-solve live — then solve for the full 2D temperature field to BS EN ISO 10211.

Open ΨMonkey — free, no sign-up

What happens in the video, second by second

The clip has no narration, so here is the whole thing written out — the same text is on the video as a caption track. Every figure below is what is actually on screen at that moment.

  1. 00:00 Build-up assistant open. ΨMonkey opens with its build-up assistant, listing a cavity wall layer by layer from outside to inside.
  2. 00:02 Pick the E5 standard SAP junction. A standard SAP junction is chosen from the drop-down: E5 — ground floor, suspended beam and block.
  3. 00:04 Live Ψ = 0.071 W/(m·K). The junction cross-section draws itself and a live result appears: Ψ = 0.071 W/(m·K), f_Rsi 0.862.
  4. 00:06 Edit the PIR insulation thickness. The PIR insulation thickness is edited in the layer list, from 100 mm upwards.
  5. 00:09 Ψ re-solves to 0.062 W/(m·K). Ψ and f_Rsi re-solve on every keystroke. At 150 mm of PIR the live Ψ settles at 0.062 W/(m·K).
  6. 00:11 Draw the junction onto the grid. “Draw junction onto grid” paints the whole build-up onto the 2D modelling canvas.
  7. 00:13 Set boundary conditions and solve. Materials, surface boundary conditions and edge conditions are set on the canvas, then Solve is pressed.
  8. 00:15 The 2D temperature field, solved. The 2D temperature field renders in colour. Results: Ψ = 0.062 W/(m·K), f_Rsi 0.873, minimum internal surface temperature 17.47 °C, 235 iterations, converged.
  9. 00:19 End card. Closing card — ΨMonkey, the free 2D thermal-bridge calculator, Ψ-values to BS EN ISO 10211.

What you're seeing

That is the whole loop: junction in, build-up adjusted, Ψ out. Everything in the clip is free in your browser — you only pay if you export a Building Control PDF, at £35 +VAT a junction.

Full detail — method, standards, pricing and FAQs — is on the ΨMonkey page.

The other demos

Seen enough?

ΨMonkey works exactly like the clip — free in your browser, no account. Open it and try your own numbers.

Model a junction — free or call 01202 623236