This is a whole-house wet UFH layout: warm water in pipe loops in overlay boards, not electric mats. The same board and pipe pack is specified on every floor — 20 mm Wundaboards with 16 mm MLCP, 150 mm centres, and a 100 m maximum loop length. Heatmiser Neo stats run the rooms. Emmetti manifolds sit on the first and ground floors; the loft loops are fed from the first-floor manifold rather than a third manifold in the loft.
The heat source on this note is a Viessmann 100-W 19 kW four-pipe boiler with weather compensation, plus a high-recovery cylinder. That pairing is a condensing system boiler feeding UFH and stored hot water. Low-temperature floors also suit a heat pump later if the cylinder coil is sized for it — the cylinder options below include a heat-pump coil — but this note is the boiler-led design as written, not a completed as-built record.
Loft
- Wundaboards 20 mm with 16 mm MLCP, 100 m maximum loop length
- 150 mm centres
- UFH pipework from the first-floor manifold (no loft manifold on this note)
- Heatmiser NeoStat X1
- Pump and blend set for different floor finishes
- Cat6 to each room from the manifold, for possible future room sensing and automation
First floor
- Emmetti manifold
- Wundaboards 20 mm with 16 mm MLCP, 100 m maximum loop length
- 150 mm centres
- Heatmiser NeoStat
- Heatmiser junction box
- Pump/mixer set for different floor finishes — leave space for later
- 5-core flex from the manifold to the boiler
- Cat6 to each room from the manifold, for possible future room sensing and automation
Ground floor
- Emmetti manifold
- Wundaboards 20 mm with 16 mm MLCP, 100 m maximum loop length, 150 mm centres
- Heatmiser Neo thermostat with a zone valve
- If the ground floor is multi-zone: add a Heatmiser junction box, stats, and actuators
- Pump/mixer set for different floor finishes — leave space for later
- 5-core flex from the manifold to the boiler
- Cat6 to each room from the manifold, for possible future room sensing and automation
Boiler
- Viessmann 100-W 19 kW, four-pipe
- Weather compensation: outdoor sensor and cable to a north-west / north wall
- De-aerator and dirt filter
Cylinder
The note lists a high-recovery store that will fit the cupboard, not a single locked-in model:
- Viessmann 250 L high-recovery coil / heat-pump coil 26 kW, or twin coil
- Joule High Gain Indirect, 210/250 L, short-stand tall to the compartment size
Design reminders
- Record circuit length per manifold port. Loop length is how you balance the manifold and stay inside the 100 m MLCP limit. Write the metres against each port before the boards go down.
- Leave space for a later pump/mixer on the first-floor and ground-floor manifolds. Different floor finishes need different flow temperatures; the blend set may not go in on day one.
- The loft is served from the first-floor manifold. Size that manifold and the home-run pipework for loft loops as well as the first-floor rooms.
Misc
An alternative overlay pack is noted if a thinner build-up is required:
- Wundaboards 16 mm with 12 mm MLCP, 60 m maximum loop length
Related
- Underfloor heating vs radiators
- Why heat pumps work well with underfloor heating
- Nest underfloor heating
- Heat pumps
This is a project-specific design note and guidance for HA39NS, not a DIY install guide and not an as-built record. Information is for competent heating engineers. Gas work in the UK must be carried out by a Gas Safe registered engineer. Design UFH to BS EN 1264 and the manufacturer’s instructions; treat the system water to BS 7593.