Size infrared heat for tender plants safely. Account for structure, airflow, insulation, and seasonal targets. Get watts, heater count, and running cost instantly today.
| Length (m) | Width (m) | Height (m) | Inside (°C) | Outside (°C) | U (W/m²·K) | ACH | Safety (%) | Radiant factor | Required (kW) | Heaters @ 1500 W |
|---|---|---|---|---|---|---|---|---|---|---|
| 8 | 4 | 2.5 | 18 | 2 | 3.50 | 1.50 | 15 | 0.90 | ~4.2 | 3 |
Infrared heaters warm leaves, benches, and soil first, then air. This matches gardening needs where root-zone stability and canopy temperature matter more than whole-room mixing. In covered beds, radiant heat can limit condensation and reduce fungal pressure by keeping surfaces slightly warmer. Growers also like fast response when doors open briefly.
The calculator estimates losses through the cover and through air exchange. Demand changes quickly with insulation quality, wind leakage, wet surfaces, and your chosen inside setpoint. Use a realistic outside design temperature for your coldest nights, not the seasonal average. If you vent for humidity control, increase ACH to reflect that. Higher plant transpiration often means more ventilation.
The required output is the design power needed to hold the setpoint at the chosen conditions. Heater count divides that load by your selected unit rating and rounds up. If you plan multiple zones, size each zone separately, then sum circuits for the worst case. Consider staged control so only part-load runs most nights.
Radiant heaters work best when aimed at the crop area, not glazing. Mount height, beam angle, and spacing decide how evenly plants receive energy. Avoid shadowing from benches and trellises by overlapping coverage zones. Keep clearances from plastics, hoses, and dry mulch, and protect wiring from irrigation spray. Use thermostats, high-limit cutoffs, and suitable outdoor-rated fittings.
Improve seals around doors, roll-up sides, and vents to cut infiltration. Add double film, thermal curtains, or insulated end walls to reduce U-value. Use circulation fans to prevent cold pockets without adding outdoor air. Run heat when surfaces cool, not only when air cools, and log energy use weekly to refine inputs. Small improvements can reduce required output and operating cost noticeably. Recheck sizing after crop changes, because foliage density alters airflow and effective losses significantly.
It adjusts the heat requirement for targeted radiant coverage. Values below 1.0 assume surfaces are warmed efficiently. Use 0.80–0.95 for good aiming and zoning. Use 1.00 if coverage is uncertain or windy.
Start with 0.5–1.0 for a tight structure. Use 1.5–3.0 if you routinely crack vents for humidity. If fans exhaust continuously, calculate their airflow and convert it to ACH for your volume.
This model focuses on cover and ventilation losses. If your floor is exposed soil, ground losses are usually smaller than glazing losses. For raised floors over open air, add extra safety margin or treat the underside as added envelope area.
U-value multiplies the envelope area and temperature difference. A small drop in U-value reduces conductive loss across every square meter. Upgrading covers, adding double layers, or using thermal curtains can cut required output and monthly cost.
It estimates current using power, voltage, and power factor. Real installations can differ due to staged heaters, thermostatic cycling, and wiring losses. Use it for planning circuits, then confirm with the heater nameplate and local electrical rules.
Run the calculator for each zone volume and insulation level. Use the coldest zone and highest ventilation as the design case. Sum heater counts and circuit loads, but keep independent controls so plants get the right temperature.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.