Installer Flow Temps
title: "Flow Temperature Calculator"
description: "Estimate the flow temp needed for each room after adding Add2Rad emitters — no downloads, no forms. Just practical numbers you can use on-site."
template: page
Flow Temperature Calculator
For Installers and Heat Pump Fitters
Use this calculator to estimate the required flow temperature after adding Add2Rad — so you can design systems confidently for heat pumps or hybrid setups.
🔍 How to Use
- Enter the room size in square metres
- Choose the insulation level (average or improved)
- Enter the total length of Add2Rad emitter to be installed
The result will show estimated flow temperature needed (°C) to comfortably heat the room.
🧾 Quick Lookup Table (No Calculator Needed)
| Room Size (m²) | Insulation | Existing Radiator (W) | + Add2Rad (m) | New Emitter Output (W) | Est. Flow Temp (°C) |
|---|---|---|---|---|---|
| 15 m² | Average | 850W | 4m | 1210W | ~42°C |
| 20 m² | Average | 1200W | 5m | 1650W | ~45°C |
| 10 m² | Good | 600W | 3m | 870W | ~35°C |
| 25 m² | Average | 1600W | 6m | 2140W | ~48°C |
Assumptions:
– Add2Rad outputs ~90W/m @ 55°C flow
– Low-temp system designed to ~45°C or below where feasible
⚠️ These figures are illustrative. Always confirm with building heat loss calculations.
🔧 Field Test Method (No Tech Required)
- Install Add2Rad temporarily (use 1–2m sample)
- Set boiler or flow controller to 50°C
- Run until room temp stabilises (30–45 mins)
- Confirm surface and room temperature delta
This quick method can confirm whether a system is “heat pump ready” before full rollout.
👨🔧 Why This Page Exists
You're a professional. You don’t need hand-holding — you need confidence that this setup keeps your customer warm and hits design temps for heat pumps.
Add2Rad makes this calculation simpler because:
- Each metre adds ~90W of emitter area
- You can customise room-by-room
- It works with existing radiators and pipework
📬 Want a Full Excel Calculator?
We’ve put the full version into a spreadsheet with heat loss math, design temp presets and printable output.
More Tools
Add More Heat. Radically Less Disruption.