This article collects the questions that come up when working with the underfloor heating module after the first drawing: why something is not visible, what a warning means, how to fix something. If you are just starting, go through the step-by-step guide first: how to use the underfloor heating module. The EN 1264 calculation model is explained in the guides on pipe spacing and loop length and on flow temperature.
Still gathering information? Start with the planning checklist. Already have a design or quote? Read what an underfloor heating design should include.
What is new in the app this October: the October 2026 update.
Rooms and sections
The room is not calculated. A section drawn on the plan must be assigned to a room. Click it, and in the section panel pick the room in the "Room" field. The list in the side panel shows rooms only. A section with no room has its own "Unassigned sections" message in the notice strip above the list, and its "Assign" link opens that section. Rooms come from the heat loss calculation (the import button in the panel, with the demand and temperature; the label comes from the room's name there, e.g. "1/12") or you add them by hand with "Add", giving a name, floor, demand in watts, type (standard up to 29°C floor surface, or bathroom up to the room temperature + 9 K, i.e. 33°C at 24°C - EN 1264-3, 4.1.1.4) and temperature.
The room balance. The room list shows for each room the underfloor output at the current parameters (e.g. 35/30°C) against the demand: the surplus in W in green or the shortfall in W in orange. Hovering over a row highlights the room on the plan. Clicking opens the room's screen: the figures ("Area", "Floor output", "Demand"), then "Loops", and last "Settings" with the "Name" and "Number" fields. The demand is the room's design heat loss, from the heat loss calculation or typed in, and the floor is sized on that whole demand (EN 1264-3, Formula (5)). Heat lost downward through the floor is not subtracted from it - it enters only the loops' flow.
The notice strip. Above the room list is one strip; the "‹ 1/3 ›" arrows step through the notices. Pressing a notice shows the full sentence, an explanation and its fix, and its link takes you to what it is about.
The free loop. On a free account one loop is fully calculated: the first one you assign to a room - the message "One loop fully calculated on your free account: ..." names it. That room's totals show when the loop is the only one in it. On the free plan we calculate a few projects at a time, so the first loop in a new project may be calculated with a delay, with a date on screen; an unlocked project is calculated in full right away.
A room on the wrong storey. In the room's edit view pick "Move to storey". Rooms with drawn loops are tied to their storey's plan and cannot be moved while the loops exist. The update from the heat loss calculation ("Update data from the heat loss calculation?") moves only rooms without loops. Room names follow the heat loss calculation; a name you changed by hand in the underfloor module is replaced only after you confirm.
Loops, lengths and splitting
A loop too long. The length is computed from the real geometry together with the run to the manifold. The limits depend on the pipe: 16x2 - a warning from 80 m, hard limit 90 m; 17x2 - 90 and 100 m. A loop with issues has a tinted "N issues" header with the fix links "Spacing N mm" and "Split"; the section drawer also shows "Consider splitting this section". With the automatic "Split" you do not pick a direction: the app chooses the cut lines itself and may divide the section into several areas ("Section split into smaller loops (N)"). The arrow beside it opens "Choose the split" with a grid and the expected lengths. When the automatic split fails, you see "No automatic split found - choose the split from the arrow." Beside the storey tabs, at the top left of the canvas, a "Split N long loops" recommendation appears, which finds cuts for the whole storey at once and shows how many sections can be split. Each part after the split has its own run - the split divides the pipe in the room, not the way to the manifold.
Pipe layout. By default "Auto" chooses between a spiral, a classic meander and a bifilar meander and says why ("High confidence spiral for a simple rectangular room", "Bifilar meander covers a narrow room better"). You change the layout in the section drawer in the "Pipe layout" field, and the pipe direction horizontal or vertical. When a shape has no ready drawing, the app says "This section shape is best split into smaller areas" instead of drawing a faulty layout.
Editing node by node. "Edit nodes" in the drawer copies the generated layout as a manual drawing with editable nodes; from then on parameter changes do not redraw it. "Restore auto" discards the manual changes and generates the layout anew. The "Draw pipes manually" tool (O) draws a pipe from scratch inside a section; the list of such sections is in the tool panel under "Hand-drawn pipes".
Holes in a section. Right-click the section and pick "Cut an opening" (e.g. a column, stairs) - the loop avoids the cut-out area. The same menu has "Duplicate section".
A floor without a loop. In the section's settings, the "Heating loop" switch turns the loop off: the section stays on the drawing as a floor with no circuit and no supply route. The report describes each room without a loop on its own, with the supply routes of other loops that cross it and their length.
Flow, spacing and parameters
A small flow in one loop. The supply temperature is set by the leading loop (EN 1264-3, 4.1.3.3); the other rooms need less, so their loops run a wider spread and a smaller flow. That is normal, and the app does not flag it. Each loop is set on the manifold to its own design flow, as the "Flow meters" window shows it (EN 1264-4, 4.1).
Spacing larger than recommended. The spacing warning means that at the project parameters the room's demand needs denser pipe. The loop's issues and the room's screen have a "Spacing N mm" link (full name: "Set the recommended spacing (N mm)"). For the whole storey, an "Apply the recommended spacing" recommendation appears beside the storey tabs - with a preview of whether any loop would exceed the recommended length because of it. Two recommendations at once fold behind one "2 recommendations" button. The recommended spacing is the widest of 200, 175, 150, 125 and 100 mm at which the floor covers the demand; the action only tightens the pipes and leaves hand-drawn loops alone. When the demand exceeds the floor's output even at 100 mm, the app says so plainly: check the supply temperature and the covering, or add a radiator.
Your own spacing. The spacing field in the section panel and in the panel for several selected sections offers 100, 150, 200, 250 and 300 mm, and "Other...", where you type a value from 50 to 300 mm in 5 mm steps. Any other value is refused with "Enter a multiple of 5." This applies to the underfloor heating module; the heat pump module and the public loop calculator keep five fixed values.
Edge zone. The "Edge zone" field in the section drawer tightens the spacing along the walls to 100 or 150 mm. "Zone depth" is 0.5 m, 1.0 m or a value you type, up to 1.0 m (EN 1264-1, 3.2.6). You choose the walls: on the drawing each wall of the selected section has its own band, and a click on a band turns it on or off. The "Walls with the zone" list in the panel does the same and shows the zone's area. A meander tightens only the walls parallel to its rows; for a wall the pipes run into, the panel suggests changing the pipe direction. The loop's output counts the zone as its own area, with a 35°C floor surface limit (EN 1264-3). The zone works only for generated layouts - a manual drawing stays without the tighter band.
Project parameters. The "Project parameters" dialog (from the "..." menu on the toolbar) has three parts: "Temperatures", "Floor" and "Pipe layout". It sets the supply and return temperature (a new project: 35/30°C), the pipe, the default floor covering, the screed over the pipe (typically 45 mm), the "Material over the pipe" (cement screed, anhydrite screed or concrete, each with its conductivity λE from EN 1264-2, Table C.1), the run pair spacing and the "Pipe distance from wall", and shows the design spread and the required supply. The parameters belong to the whole project, not to one storey. The floor output is computed to the EN 1264-2 thermal characteristic from the pipe actually laid in the section, and the flow to EN 1264-3: G = 0.86 · (Q + Φ_FB) · (1 + Ro/Ru) / σ, where Q is the loop's output to the room and Φ_FB its share of the loss through the floor, split between the room's loops by area.
Pipe distance from wall. How far the outermost pipe sits from the edge of the section. 100 mm by default; 50, 80, 150 and 200 mm to choose from, or "Other..." from 30 to 500 mm. A change in the project parameters re-lays the existing sections. A section can have its own distance - the first option in its settings, "Project default (X mm)", returns to the project's value. A hand-drawn loop has no such field. Below 80 mm a meander turns on its 80 mm bend radius, so row ends may sit further from the wall.
Return temperature not above the room temperature. The floor then gives off no heat - raise the return in the project parameters. The supply must be higher than the return, otherwise the flow is not computed.
Manifolds and runs
You place the manifold with the "Manifold" tool (M) with two clicks at the ends of the cabinet. In its panel you set the number of ports; the warning "More circuits connected than ports" means you need to increase the number of ports or add a second manifold. The "Flow meters" link at the foot of the side panel opens a window with the storey's totals at the top: area, pipe, "Water in the pipes, without manifolds" (the litres in the loops and runs), flow and "Heat in the water" - the heat the water carries to the manifolds (rearranged Formula (13) of EN 1264-3). After an import from the heat loss calculation, the building design heat loss sits below them, marked "for sizing the heat pump". The loops are grouped by manifold, in port order, with the columns "Port", "Loop" and "Room"; loops on no manifold come last. Each loop has "Q [W]", "σ [K]", l/min and Δp (the pipe in the room and both runs, with a warning above 35 kPa from EN 1264-3), so l/min = 0.86 · Q / σ / 60 holds on every row. The PDF report has the same table. The window counts every drawn loop, and loops without a flow get one sentence with the reason: their rooms have no heat loss entered - pull it in from the heat loss calculation or type it in the room.
The cabinet's size follows its port count (2 to 14): after a change it grows or shrinks at the far end, and port 1 stays where it is. "Direction" sets which side port 1 is on; you can also turn the cabinet with the handle above it or with O, always by 90°.
You draw the run (route) with the "Draw supply route" tool (R) from a section or a manifold; Enter finishes the route at the last point, Backspace removes the last point, Esc cancels. You set the run pair spacing by default in the parameters and for a single route in its panel; select several routes and right-click to change the spacing of many at once. With the grid on (G), a point placed beside a room wall does not jump onto the grid: it lies along the wall, so the outer pipe of the pair runs against the wall. After you move a manifold with automatic runs, the app offers "Route the feeders again"; the issues of a loop with no run carry the same link.
To remove a bend you no longer need, double-click it, or click it and press Delete; a double-click on a segment adds one. The two ends of a run cannot be removed this way.
A route that does not connect to the loop. The loop's issues say what to change. "The pipes cannot join the loop at this point on the wall. Move the end of the route along the section wall." - moving the route is enough. "The selected pipe layout cannot be bent in this section at N mm spacing. Choose Auto or another layout, change the spacing or split the section - moving the route will not fix it." - the problem is in the section itself, not in the route.
Storeys
Storeys are tabs above the drawing. "Add storey" offers "Storey above" or "Basement (below)"; you rename by clicking, and "Delete storey" removes its backdrop, rooms, loops and manifolds with no undo. Storeys imported from the heat loss calculation are created by themselves. On a free account you draw on one storey - instead of the add menu you see "One floor on a free account", which leads to unlocking the project; storeys from the heat loss calculation do not count towards that limit.
Backdrop and calibration
Formats and limit. PDF, PNG, JPG, HEIC, DWG or DXF; with a multi-page PDF you pick the page in the "Select page" dialog. The plan file can be up to 25 MB. An iPhone photo (HEIC) is converted to JPG, turned upright and stripped of its metadata, location included.
Changing and rotating the backdrop. "Background settings" (an icon on the toolbar) let you change the scan, rotate it by any angle or reset the project. Rotate before drawing - drawn sections, manifolds and routes do not rotate together with the backdrop. Rotating and cropping keep the scale. "Replace background" (confirmed with "Replace the background?") clears it: "The new plan has its own scale - set it again with the ruler tool. Until then, areas and pipe lengths are not calculated."
Calibration. The "Calibration" tool (C): two points a known distance apart and the distance in centimetres; the range message reminds you not to type metres. Recalibration is in the project parameters dialog ("Calibration set - Re-calibrate"). Calibration is per storey - every new one needs its own.
Snapping. When drawing geometry was detected in the file, drawing snaps to walls. You toggle the grid with G and set its origin with Alt and a click; Shift forces a 90° angle, Shift with Alt 45°, and Ctrl (Cmd on a Mac) draws without snapping.
Export and other
The printable plan and the full PDF are described in the article on reports; the messages about the plan preview before export are there too. "Report notes" (the notes icon) go at the end of the PDF. The "Materials" link beside "Flow meters" opens the bill of materials for the wholesaler.
Keyboard shortcuts and gestures are in the "?" dialog on the module bar; the full list is in the "Useful keyboard shortcuts" section of the guide. The most important: V select, H move a section or manifold, P section, M manifold, R route, O manual pipe, Space with dragging pans the view, Ctrl with scrolling zooms, Ctrl+Z undoes.
With exactly one manifold selected, O turns it by 90° instead of picking the manual pipe tool.
"Project was changed on another device" - someone (or you in another tab) saved a newer version; click "Load newer version". "Failed to save the floor plan for storey" - the rest of the project is saved; upload the backdrop again with "Upload again".
"A new generation of drawings" - older projects get an offer to update their layouts and lengths to the new generator. Before updating, download the existing PDF with the button in that dialog, because the layouts and metres will be recomputed; "Later" postpones the decision.
Drawing needs a computer or a tablet. On a phone the module shows the project's documents: download the report and the bill of materials one by one or together as a ZIP (on a free account, only the report preview); the print plan is set and downloaded on a computer.
AI sections on your floor plan
You do not have to trace the sections by hand. Once the plan is uploaded, Algo AI reads its rooms, doors and windows, and the app draws the rest with no AI model, so the same plan gives the same drawing: the loops with their pipe layout, the supply runs to the manifold by the shortest way through the doors, edge zones and movement joints. Algo AI takes the scale from the plan's dimensions or from the room areas printed on it, and asks you to calibrate only when it cannot read one. You review the proposal on the drawing and apply it. One generation per account is free - the first read of a plan spends it, not Apply - and everything stays editable. The whole path is in underfloor heating from a floor plan.
Algo AI names the rooms in the draft from the text on the plan, and gives rooms with no text a name in the app's language. While the draft is open, the drawing is locked: "Apply or discard the draft to edit the drawing." Panning and zooming still work. A request still waiting for a plan or a scale can be cancelled free of charge ("Cancel the request?"), and after discarding a draft you can ask for a new one with "Draw again". On a storey with no manifold, the app places one itself, one per 14 loops, and says so in the draft: "Manifold placed automatically - move it if it belongs elsewhere, then press Recalculate." A manifold already on the storey is never moved. You correct doors and windows in the draft. When no run can reach a loop, the app does not force one: the loop's panel gives the reason, and you draw that run by hand.