Greenhouse Heating & Cooling Load Estimator
Rough heating and cooling load estimation using a simplified conduction + ventilation + solar gain model. Enter dimensions, glazing type, and design temperatures to see approximate peak loads and equipment capacities. Educational only, not an engineering design.
Greenhouse Dimensions
Winter Design Temperatures (Heating)
Summer Design Temperatures (Cooling)
Typical range: 10-25%. Added to peak load for equipment capacity recommendation.
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Enter your greenhouse dimensions, glazing type, and design temperatures, then click Calculate Load Estimates to see rough heating and cooling load estimates.
Understanding Greenhouse Heating & Cooling Loads
Maintaining proper temperature in a greenhouse is critical for plant health and productivity. This educational tool helps you understand the basic concepts behind greenhouse heating and cooling load calculations.
Heat Transfer Mechanisms
Greenhouses gain and lose heat through three main mechanisms:
- Conduction: Heat flows through the glazing material (glass, polyethylene, polycarbonate) from warm to cold areas. The rate depends on the U-value and temperature difference.
- Infiltration: Air leakage through gaps, doors, and vents exchanges warm indoor air with cold outdoor air (winter) or cool indoor air with hot outdoor air (summer).
- Solar radiation: Sunlight passing through the glazing heats the interior. This is beneficial in winter but adds to cooling load in summer.
The Basic Load Equations
This tool uses simplified steady-state formulas:
Envelope Load: Q = U × A × ΔT
Infiltration Load: Q = V × ACH × ρCp × ΔT
Solar Gain (cooling): Q = Floor Area × Solar Factor
Where U = thermal transmittance, A = envelope area, ΔT = temperature difference, V = volume, ACH = air changes per hour, ρCp = volumetric heat capacity of air.
Glazing Materials Compared
| Glazing Type | U-Value (BTU/hr·ft²·°F) | Relative Performance |
|---|---|---|
| Single Polyethylene | ~1.05 | Low insulation |
| Single Glass | ~1.02 | Low insulation |
| Double Polyethylene | ~0.62 | Moderate insulation |
| Polycarbonate (twin-wall) | ~0.53 | Good insulation |
| Double Glass | ~0.49 | Best insulation |
Key Design Considerations
- Climate zone: Colder regions need more heating capacity; hot climates need more cooling.
- Crop requirements: Different crops have different temperature ranges. Tropical plants need warmer conditions.
- Thermal mass: Water barrels, concrete floors, and soil beds store heat and moderate temperature swings.
- Ventilation: Natural or mechanical ventilation affects both temperature control and humidity management.
- Backup systems: Critical crops may need redundant heating in case of primary system failure.
Heating Options
- Hot water/steam: Boilers with piped distribution
- Forced air: Gas or oil-fired unit heaters
- Electric: Infrared heaters, heat pumps
- Radiant floor: In-floor heating for root zone warmth
Cooling Options
- Natural ventilation: Ridge and side vents, rollup sides
- Exhaust fans: Mechanical ventilation with intake shutters
- Evaporative cooling: Pad-and-fan or fog systems
- Shade cloth: Reduces solar gain
- Air conditioning: For high-value crops in hot climates
Important Disclaimer
This tool provides rough educational estimates using simplified formulas. Actual greenhouse HVAC design requires professional engineering analysis considering exact geometry, local climate data, crop requirements, ventilation systems, backup capacity, and local codes. Always consult qualified professionals for real equipment sizing decisions.
Frequently Asked Questions
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