One batch of changes, but in the module where the numbers matter most: the underfloor heating calculations have been rebuilt from the ground up and now compute to EN 1264. Below is what changed, what you will see in a project you already have, and why some figures look different from yesterday.
New features
Loop output answers to what is in the floor
Until now the "loop output" in the section drawer did not move when you changed the spacing or the pipe layout. Not a defect - an unfinished model: the loop was showing its share of the room's demand, split by area, and that figure has by definition nothing to do with the pipe.
The drawer now names both quantities separately. Loop output is what the loop delivers at the project parameters, computed from the pipe actually laid in the section: effective spacing = area / in-room pipe length. So it answers to the spacing, to the layout (a spiral lays more pipe than a meander), to the edge zone, to the covering and to every node you move on a hand-drawn loop. Demand is the loop's share of the room's heat load - what the loop has to carry, and what the flow is derived from. Where a room has several loops, the share follows what each can deliver, not its square metres.
The recommended spacing is no longer a three-step table either. It is the widest spacing (up to 200 mm) at which the floor's output covers the room's specific load - at the project temperatures, with this section's covering, under the surface temperature limit. The recommendation and the room balance read one model, so one no longer says "150 mm" while the other says "deficit".
Thermal and limit characteristics from EN 1264-2
Output per square metre is now computed on the standard's thermal characteristic (type A - pipe in screed): spacing, the covering's thermal resistance, the screed cover over the pipe and the pipe diameter give the floor's heat transmission coefficient, multiplied by the logarithmic water-to-room temperature difference. Above it sits the limit characteristic - the output at which the surface reaches 29 °C, or 33 °C in a bathroom. The standard's tables are in the code with the interpolation the standard prescribes, and every transcribed value is checked by a test against the text of the standard itself.
What it changes in numbers: at 35/30 °C on tile at 150 mm the floor gives 51 W/m² instead of 50, at 200 mm 46 instead of 42, at 300 mm 36 instead of 29 - the old model was too cautious at wider spacings. The ceiling from the surface limit is 100 W/m² instead of 90 in a 20 °C room, and less in practice, because the floor between the pipes is cooler than the floor above them. The project parameters gained one field: screed over the pipe (45 mm by default - a 61 mm screed over a 16 mm pipe laid on the insulation).
Each loop's spread and flow from EN 1264-3
Every loop used to run the same spread and the same flow formula. The standard does it differently, and so does HeatAlgo now: a loop asked to deliver less than it could at the project's supply temperature runs a wider spread and a smaller flow - exactly what happens once its valve is set on the manifold. A single loop's spread has a ceiling of 10 K (never below the design spread): beyond it the water would return a fraction of a degree above the room, at a flow so small the standard stops describing it. The section drawer shows the loop's return, and the rotameter table in the report has a new column with each loop's return.
The flow also carries the loss downward: some of the heat from the pipe leaves through the slab before anything reaches the room. That loss factor comes from the floor element in your heat load calculation (its U-value), and for a room typed by hand from the minimum insulation EN 1264-4 requires. The building flow is the sum of the loop flows.
The project parameters now show the required supply: the temperature at which the leading loop (bathrooms excluded) runs at the design spread. If the project's supply is well above it, the "flow below 0.5 l/min" warning now tells you something true and names it: lower the supply or widen the spacing, do not tighten the pipe. A return set no higher than the room temperature gets its own warning - such a floor gives off no heat, and the report says so instead of showing zero and "deficit".
A note on the numbers: floor output is computed at the thermal resistance of the covering you pick for the section (tile 0.05, vinyl 0.08, wood 0.12, carpet 0.15 m²K/W). EN 1264-3 assumes 0.10 for residential design and says to take higher values where they apply - so for tile and vinyl the required supply and the balance come out more favourable than the standard's procedure would give. The methodology page in the report says so.
The floor's own loss is not counted twice
A heated floor supplies the loss through itself from underneath, so the room does not need it from above. The import from the heat load calculation records the loss of the room's floor elements, and the balance compares the loop output with the load less that loss; the heat load column in the report keeps showing the full load, and a footnote under the table says how much of it the floor supplies. Typing a load by hand clears that deduction - we do not know what a typed figure contains.
Improvements
- A new project starts at 35/30 °C, not 30/25. The old pair could not cover 40 W/m² at any spacing, so every new project opened on a deficit before anyone touched the parameters.
- A hand-drawn loop is computed from the drawn pipe, not from the spacing in a select that describes nothing for it. The spacing warning judges the drawn density; the loop-length warning judges the drawn metres.
- Heat pump sizing checks underfloor heating on the same characteristic as the underfloor module. It used to have a less accurate one of its own and could disagree with the underfloor report by over ten percent on the same floor. A covering the pump module has no name for is computed at 0.10 m²K/W - the resistance the standard assumes.
- The flow-temperature guide and the room pages publish tables from the new characteristic; the sentences about "HeatAlgo's model" are gone, because the model is now the standard's.
Fixes
- The "q out of range" warning names the number. It says how many W/m² the room needs and that no recommended spacing covers it at these parameters, instead of repeating a threshold from the old table.
What you will see in an existing project
Loop outputs, flows and recommended spacings recompute when you open the project - the inputs do not change. A room's balance will usually come out slightly better (the new characteristic gives more at 200 and 300 mm), and the flows of loops that delivered less than they could will drop. A project saved at the old 30/25 °C will show more spacing and output warnings than yesterday: the same rooms the old table could not name. This applies to heat pump projects too - the sizing module computes underfloor heating on the new characteristic, so a reopened project may show a different supply temperature and a different SCOP than the report you already handed the client; the new figures are the right ones. To check where a figure comes from, the "Calculation methodology" page of the report lists every formula with its clause number in the standard.
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