About this calculator
This calculator helps estimate how many insulation boards, how much adhesive, how many mechanical anchors, and how much reinforcing mesh a wall needs for insulation (an ETICS system) — enter the wall dimensions, insulation thickness, and board size, and add any openings separately so they are deducted from the calculated area. Works for facade insulation with polystyrene, mineral wool, or another board-form insulation.
Formula
The calculator converts the wall and board dimensions to whole millimetres, then:
wall area = length × height
openings area = Σ (opening width × opening height)
net area = wall area − openings area
boards required (excl. waste) = ceil(net area / (board length × width))
waste boards = ceil(board count × waste% / 100)
total boards = board count + waste boards
insulation volume = net area × insulation thickness
adhesive mass = net area × adhesive coverage (kg/m²)
anchor count = ceil(net area × anchors/m²)
mesh area = net area × (1 + overlap% / 100)
R = insulation thickness / λ (ISO 6946)
Boards are joined with no gap (edge to edge, with no joint-width input), so the board
"pitch" is simply the board's own area. Openings are deducted as net area, not as
individual board subtraction — the same logic as the masonry-wall calculator. Insulation
volume is computed exactly from the geometry (net area × thickness) — waste is not applied
to it. Mesh area is increased by the overlap percentage, since adjacent mesh strips are laid
overlapping, not edge to edge. The thermal resistance R is computed by the ISO 6946 formula
R = thickness / λ — this is only the insulation layer's own resistance, not including the
wall's other layers (masonry, render, and so on).
Worked example
Defaults: wall length 4 m, height 2.5 m, no openings, insulation thickness 100 mm, board 1200×600 mm, λ = 0.035 W/(m·K), adhesive coverage 5 kg/m², 6 anchors/m², mesh overlap 10%, waste 10%.
wall area = 4 m × 2.5 m = 10 m² (no openings, so net area is the same)
boards excl. waste = ceil(10,000,000 / (1200×600)) = ceil(13.89) = 14
waste boards = ceil(14 × 10 / 100) = 2
total boards = 14 + 2 = 16
insulation volume = 10 m² × 0.1 m = 1.0 m³
adhesive mass = 10 m² × 5 kg/m² = 50 kg
anchor count = ceil(10 m² × 6) = 60
mesh area = 10 m² × (1 + 10/100) = 11 m²
R = 0.1 m / 0.035 W/(m·K) = 2.857... ≈ 2.86 m²·K/W
For these inputs the calculator returns exactly this: 16 boards total (14 excl. waste + 2 for waste), 1.0 m³ of insulation, 50 kg of adhesive, 60 anchors, 11 m² of mesh, and R = 2.86 m²·K/W.
FAQ
Are openings (doors, windows) deducted from the board quantity? Yes. Every added opening is deducted from the wall area before computing every quantity — boards, adhesive, anchors, and mesh.
Does the R value cover the whole wall assembly?
No. Using the ISO 6946 formula R = thickness / λ, the calculator computes only the
insulation layer's own thermal resistance — the results panel shows a warning to that
effect. The whole wall's combined resistance (masonry, render, and other layers) will be
higher, but needs to be computed separately.
What determines the λ (lambda) value? λ (W/(m·K)) is a value you enter, printed on your specific chosen insulation product's technical data sheet — it differs by product (polystyrene, mineral wool), so the calculator doesn't derive it itself.
How many anchors should be allowed per square metre? The default is 6 anchors/m², but the real density depends on building height, wind load, and substrate type — that's set by the specific ETICS system's technical approval, which this calculator doesn't evaluate.
Are the anchors and the layer cross-section shown in the drawing accurate? No, both are schematic. The anchor marks in the drawing show only an illustrative "W" pattern (one at each corner, one at the centre), not each board's real anchor count or position. In the layer cross-section, only the insulation layer's own thickness is real (your own entered value) — the wall, adhesive, mesh, and render layer thicknesses in the drawing are fixed illustrative constants, not real dimensions.
Assumptions and limits
meta.standards cites ISO 6946 — the source of the R = thickness / λ formula, applied only
to the insulation layer. No standard was found for the board/adhesive/anchor/mesh quantity
calculation — these depend on the specific ETICS system's manufacturer and technical
approval, not one universal standard.
λ, adhesive coverage, anchor density, and mesh overlap percentage are user inputs with sensible defaults, not constants derived from a standard.
The R value covers only the insulation layer — not the whole wall assembly — and the calculator's own R-value result says so explicitly, citing ISO 6946.
The anchor marks in the drawing show a representative pattern (one near each corner, one centred), not a literal layout — the real per-board count and position depends on the specific ETICS system's technical approval (wind zone, building height, edge and corner zones), none of which this calculator models. Compare against "Anchors" in the results for the total quantity, not a count of the marks shown.
The layer cross-section drawing is schematic too: only the insulation layer is drawn to its real thickness. The wall, adhesive, mesh, and render layers are illustrative only — this calculator has no input for their thickness. In the elevation drawing, the row/column count is decimated for a large area so the SVG stays legible.