“How many heaters” rarely has a single answer because a terrace is almost never one zone. The pro approach is to size by genuinely occupied zones, then validate the geometry (height/angle/distance), wind exposure and the level of enclosure.
1) Rule #1: size zones, not square metres
“Table” zone
Seated, static: needs consistent, even comfort.
“Lounge” zone
Larger area, varied posture: prioritise wide, gentle coverage.
“Walkway / waiting” zone
Short stay: a small top-up is enough—don’t oversize it.
2) The pro method in 5 steps (simple & repeatable)
- Draw occupied zones (tables, lounge, bar) and note dimensions.
- Validate mounting constraints: available height, structure (wall/ceiling), obstacles.
- Classify exposure: open / under pergola / partly enclosed / enclosed (veranda-like).
- Choose a coverage strategy: multiple aimed points vs one very powerful unit.
- Add a “reality” buffer: prevailing wind, large voids, table rotation, peak occupancy.
3) Why “one big heater” is often a mistake
Radiant density issue
One unit often pushes you to mount higher or spread wider. Result: radiant density drops and warmth feels weaker.
Comfort issue
Too hot directly underneath, too cool on the sides. Multiple well-aimed points deliver more even comfort.
4) Quick guide: which terrace profile means more (or fewer) units?
| Configuration | Impact on quantity | What works best |
|---|---|---|
| Very open & windy | ↑ (more points, more targeted) | Strict zoning, closer mounting, precise aiming |
| Under pergola / canopy | ↔ (more stable sizing) | Even coverage, regular distribution |
| Partly enclosed (screens/panels) | ↓ (lower losses) | Fewer units, ideally zone-controllable |
| Enclosed (veranda-like) | ↓ (near-indoor logic) | Soft distribution + control to avoid overheating |
5) Real examples (logic, not “magic”)
Example A: 2 tables under a pergola
- Zones: 2 tables (2 separate occupied zones)
- Strategy: 1 point per table, or 2 points covering both depending on layout
- Goal: heat seating, not circulation paths
Example B: Large open lounge area
- Zone: sofa + armchairs (wide occupied zone)
- Strategy: multiple aimed points to avoid a central “hot spot”
- Goal: soft, distributed comfort for varied positions
Example C: Restaurant, bar and hotel terrace with table rotation
- Zones: table rows + waiting areas
- Strategy: zoning by “rows” + zone control
- Goal: power only occupied areas and handle peak times
6) Final checklist (anti-mistakes)
Geometry & mounting
- Realistic mounting height (not “higher to cover more”)
- Aim into the occupied zone (seating)
- Obstacles: beams, lights, awnings
- Safety clearances respected
Context & use
- Prevailing wind / airflow corridors
- Enclosure level (screens/panels)
- Real occupancy (peak periods)
- Need for zoning/control (pro)
7) FAQ
Is there a reliable “kW per m2” rule?
How do I know if I have too many or too few heaters?
Why is zoning critical in hospitality?
Pro tip: start with the zone plan and mounting geometry. The “number of heaters” follows from that.
The expert blog for premium outdoor infrared heating
Expert insights and guides on premium infrared outdoor heating. Technical analysis and radiant innovations for pergolas and professional terraces.
