In short: you need about 10m of pipe per m² at 100mm centres, 6.7m per m² at 150mm centres and 5m per m² at 200mm centres, plus the tails to and from the manifold. Each loop must stay under a maximum length (about 80m for 12mm pipe, 100m for 16mm and 120m for 20mm) and every loop needs its own manifold port. Add your rooms below and the calculator works out the pipe, loops, coils, manifold and fixings.
What you need
Parts list
How the calculator works
- Pipe in the floor = area x pipe per m². At 150mm centres that is 1,000 / 150 = 6.7m per m².
- Tails: each loop runs from the manifold to the room and back, so it adds twice the distance to the manifold.
- Loops: a room is split into as many equal loops as it takes to keep every loop, tails included, under the maximum loop length.
- Coils: a loop must be one unbroken length with no joints in the floor, so loops are fitted into coils whole. The calculator picks coil sizes that leave the least waste.
- Manifold: one port per loop. Our Dualmix manifolds run from 2 to 12 ports. Over 12 loops, use two manifolds.
- Eurocone cores and support bends: two of each per loop, one for the flow and one for the return.
- Tacker clips: one about every 500mm on straight runs and three on each bend. The number of bends is estimated from the room shape, and 5% is added for spares.
- Edge insulation: estimated from the room area as a square room, plus 10%. Measure your rooms for an exact figure.
Which pipe centres should I use?
150mm suits most rooms on a boiler. Heat pumps run cooler, so they often use 100mm or 150mm centres to get enough heat into the room. 200mm can suit well insulated rooms with low heat loss. The right answer comes from the room's heat loss.
Maximum loop lengths
The defaults are common guide figures: about 60m for 10mm pipe, 80m for 12mm, 100m for 15mm and 16mm, and 120m for 20mm. Longer loops need more pump head to push water round. If you have a design with flow rates, use its figures.
Frequently asked questions
How much underfloor heating pipe do I need per m²?
About 10m per m² at 100mm centres, 6.7m per m² at 150mm centres and 5m per m² at 200mm centres. Then add the tails from each loop back to the manifold.
How long can an underfloor heating loop be?
As a guide, about 80m for 12mm pipe, 100m for 16mm pipe and 120m for 20mm pipe, including the tails to the manifold. Longer loops need more pump head.
How many manifold ports do I need?
One port per loop. A 30m² room at 150mm centres with 16mm pipe usually needs two or three loops, depending on how far it is from the manifold.
Can I join underfloor heating pipe in the floor?
It is best not to. Each loop should be one unbroken length from the manifold and back. That is why the calculator fits whole loops into coils.