Calculator Inputs
Example Data Table
| Room | Area (m²) | System | Tube Spacing (mm) | Heat Load (W) | Loops | Total Tube (m) | Flow (L/min) |
|---|---|---|---|---|---|---|---|
| Living Room | 27.00 | Slab Embedded | 150 | 1,226.00 | 2 | 194.40 | 2.51 |
| Bedroom | 16.80 | Dry Panel | 200 | 816.00 | 1 | 90.72 | 1.95 |
| Office | 12.00 | Staple Up | 150 | 724.00 | 1 | 86.40 | 1.73 |
Formula Used
Area = Length × Width
Volume = Area × Ceiling Height
ΔT = Indoor Design Temperature − Outdoor Design Temperature
Envelope Loss = Area × Insulation Factor × ΔT
Infiltration Loss = 0.33 × Air Changes per Hour × Volume × ΔT
Perimeter Loss = Exposed Perimeter × Edge Factor × ΔT
Design Heat Load = (Envelope Loss + Infiltration Loss + Perimeter Loss) × (1 + Margin)
Required Output = Design Heat Load ÷ Floor Area
Estimated Floor Output = ((Mean Water Temperature − Room Temperature) × 5.4 × System Factor × (200 ÷ Tube Spacing)) ÷ (1 + 2.2 × Floor R-Value)
Tube Length ≈ (Area ÷ Spacing in meters) × 1.08
Flow Rate = Design Heat Load ÷ (4180 × Water Temperature Drop) × 60
These equations provide an engineering estimate for conceptual sizing. Final construction design should still confirm structural buildup, manifold pressure drop, pump head, and manufacturer limits.
How to Use This Calculator
- Enter the room size, ceiling height, and indoor and outdoor design temperatures.
- Choose the insulation quality, edge insulation quality, and radiant system type.
- Provide floor covering resistance, tube spacing, tube diameter, and water temperatures.
- Set air changes, design margin, and maximum loop length.
- Leave exposed perimeter as zero to let the calculator estimate it automatically.
- Press Calculate Heating Design to show the result above the form.
- Review the design load, output density, loop count, flow rate, and temperature guidance.
- Use the CSV or PDF buttons to export the generated results for reporting or review.
FAQs
1) What does this calculator estimate?
It estimates room heat load, required floor output, tubing length, loop count, flow rate, water volume, and a basic design adequacy check for radiant floor heating.
2) Why does floor covering R-value matter?
Higher floor resistance blocks heat transfer. Thick wood, carpet, or underlay can reduce delivered output and may require tighter spacing or warmer water.
3) What is the difference between slab, dry panel, and staple up?
Slab systems usually transfer heat most effectively. Dry panels perform well with good plates. Staple up systems often need more careful temperature and spacing control.
4) Why is airflow included in the calculation?
Air changes represent infiltration and ventilation losses. Drafty rooms lose heat faster, which increases total load and the required radiant floor output.
5) Is this tool suitable for final construction drawings?
It is best for preliminary sizing and comparison. Final project design should confirm local codes, structural layers, pressure drop, pump head, and manufacturer data.
6) Why might the design check fail?
The room load may be too high for the selected spacing, covering resistance, system type, or water temperature. Better insulation can also reduce the load.
7) What is a reasonable maximum loop length?
Many residential layouts stay near 80 to 120 meters per loop, depending on tubing size and pressure drop limits. Always verify manufacturer recommendations.
8) Can I export the calculated results?
Yes. When results are available, use the CSV and PDF buttons above the form to save the output summary for documentation or sharing.