Watch U-Monkey build up a U-value

28-second demo · silent screencast, captions included · the free U-value calculator

Stack up the layers of a wall and watch the U-value, the self-drawing cross-section and the Part L / Future Homes Standard checks update live with every change.

Open U-Monkey — 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 The element picker. U-Monkey opens on its element picker — no sign-up: wall, roof with insulation at rafter, roof with insulation at ceiling, flat roof, exposed floor, ground floor to ISO 13370 and suspended ground floor.
2. 00:05 Load the cavity wall example. “See a worked example — a full cavity wall, calculated for you” is tapped.
3. 00:07 The build-up loaded. One tap loads the build-up: brickwork outer leaf 102 mm, mineral wool slab 150 mm, aircrete block 100 mm.
4. 00:08 Layers stack, cross-section draws itself. The layers stack up with a live cross-section drawing itself alongside, labelled outside to inside, under a New build / New element / Upgrading existing selector.
5. 00:12 U = 0.21 W/m²K with the Part L checks. The U-value reads 0.21 W/m²K instantly, with the compliance chips beside it: Part L limit 0.26 met, notional 0.18 not met, FHS-level 0.15 not met.
6. 00:15 Auto-solve to a target U-value. “Hit a target U-value…” auto-solves the insulation. The tool answers: you need 180 mm of mineral wool slab to reach U = 0.18.
7. 00:20 U = 0.18 W/m²K — meets Part L notional. The build-up updates to 0.18 W/m²K and the badge flips to “Meets Part L notional”, with the ISO 13788 mould check reading f_Rsi = 0.96 ≥ 0.75 and the Building Control-ready PDF free to download.
8. 00:25 End card. Closing card — U-Monkey, the free U-value calculator, BS EN ISO 6946 and BR 443, with live Part L and Future Homes checks.

What you're seeing

BS EN ISO 6946 with BR 443 conventions, 250+ real UK products and a condensation-risk screening — completely free, including the Building Control-ready PDF.

Full detail — method, standards, pricing and FAQs — is on the U-Monkey page. The clip moves quickly, so if you would rather follow it at your own pace, the complete U-Monkey tutorial covers every step in the video and the parts that did not fit into 28 seconds.

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