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A free U-value calculator that shows its working. Build any wall, roof, floor or curtain wall layer by layer. Turn it as a 3D cutaway, and check its U-value, embodied carbon, condensation risk and fire performance against UK rules, with the maths shown.
01 / How it works
Fill in the project once. Every check after that uses the right limits for your nation, building and element.
Pick the nation, new build or renovation, the element and the building use. These set the U-value limit, the fire rules and the climate.
Start from one of 44 systems, import an IFC file, or add layers yourself. The model redraws to scale as you edit.
U-value, condensation, fire and driving rain, each with a pass or fail and the source it comes from.
Download images, a PDF report and a carbon report, export to Rhino, or send a share link.
02 / What it checks
Each result shows its working, so you can follow it, check it and quote it.
Layer resistances, surface resistances, bridged layers, and the corrections for air gaps and mechanical fixings, all set out as in BS EN ISO 6946. The result is compared with the limit for your project.
A carbon report covering stages A1 to A5, using EPD and ICE data, with a plain comparison such as car kilometres driven.
A month-by-month Glaser check to BS EN ISO 13788 and BS 5250, using the climate of the nearest station and the humidity class of the building.
Reaction to fire of every layer, checked against Approved Document B for the height of the top storey and the distance to the boundary.
The exposure zone and the cladding type set whether a full-fill cavity is suitable, from sheltered to very severe.
Cavity and framed walls, rainscreens, flat and pitched roofs, ground and suspended floors, rooflights, and curtain walls from stick to unitised. Pin options side by side and compare them.
03 / In and out
Bring in a wall type from your model, and take a drawing, report or 3D model back out.
Read wall types, roofs and curtain walls from Revit or other IFC2X3 and IFC4 files, with their layers and thicknesses.
The build-up, the drawings, every check and its sources, ready to attach to a submission.
One object per layer, named and coloured, ready to place in your model.
Copy the cutaway or 2D section as an image, copy the specification as text, or send a link that opens the same build-up.
04 / Sources
Material data and rules come from published standards and guidance, and the tool lists where each figure comes from.
The results are indicative and meant for design and teaching. Check final figures with the manufacturer or a qualified assessor.
See the UK U-value limits for walls, roofs, floors and windows, or browse the U-values of 69 common build-ups, each with its layers and a section drawing.
No account and nothing to install. Your build-ups are saved on your device.
Open the visualiser