{
    "name": "Greenhouse Heating Load Calculator",
    "url": "https://calculators.geekmidst.com/calculators/greenhouse-heating-load-calculator",
    "markdown": "https://calculators.geekmidst.com/calculators/greenhouse-heating-load-calculator.md",
    "category": "Agriculture",
    "description": "Estimate the heater size a greenhouse needs from its covering area, U-value, the inside–outside temperature difference and air leakage.",
    "summary": "Heat loss is the covering area × U-value × temperature difference, plus the heat carried out by leaking air. Size the heater for the coldest night you plan for.",
    "also_called": [
        "Greenhouse heater size calculator",
        "Greenhouse BTU calculator"
    ],
    "applies_to": "Worldwide",
    "last_updated": "2026-10-29",
    "computation": "Results are computed in the visitor’s browser on the HTML page. This API describes the calculator; it does not compute results.",
    "inputs": [
        {
            "name": "units",
            "label": "Units",
            "type": "segmented",
            "default": "metric",
            "options": {
                "metric": "Metric (m, °C, W/m²K)",
                "imperial": "US (ft, °F, BTU/h·ft²·°F)"
            }
        },
        {
            "name": "length",
            "label": "Length",
            "type": "number",
            "default": "30"
        },
        {
            "name": "width",
            "label": "Width",
            "type": "number",
            "default": "9"
        },
        {
            "name": "eave_height",
            "label": "Side-wall (eave) height",
            "type": "number",
            "default": "3"
        },
        {
            "name": "ridge_height",
            "label": "Ridge height",
            "type": "number",
            "default": "5"
        },
        {
            "name": "u_value",
            "label": "U-value of the covering",
            "type": "number",
            "default": "4"
        },
        {
            "name": "inside_temp",
            "label": "Inside temperature to hold",
            "type": "number",
            "default": "15"
        },
        {
            "name": "outside_temp",
            "label": "Coldest outside temperature",
            "type": "number",
            "default": "-5"
        },
        {
            "name": "ach",
            "label": "Air leakage",
            "type": "number",
            "default": "1",
            "unit": "air changes/h"
        }
    ],
    "outputs": [
        {
            "key": "heat_loss_kw",
            "label": "Heating load",
            "format": "number"
        },
        {
            "key": "heat_loss_btuh",
            "label": "Heating load",
            "format": "integer"
        },
        {
            "key": "conduction_kw",
            "label": "Loss through the covering",
            "format": "number"
        },
        {
            "key": "infiltration_kw",
            "label": "Loss by air leakage",
            "format": "number"
        },
        {
            "key": "surface_m2",
            "label": "Covering area",
            "format": "number"
        },
        {
            "key": "volume_m3",
            "label": "Greenhouse volume",
            "format": "number"
        }
    ],
    "formula": {
        "text": "Q = U × A × ΔT + 1206 J/(m³·K) × V × ACH × ΔT ÷ 3600;  A = walls + gable ends + roof",
        "variables": {
            "U": "heat transfer coefficient of the covering",
            "A": "covering area",
            "ΔT": "inside minus outside temperature",
            "V": "house volume",
            "ACH": "air changes per hour; air holds 1.2 kg/m³ × 1005 J/(kg·K)"
        }
    },
    "worked_example": {
        "inputs": {
            "units": "metric",
            "length": "30",
            "width": "9",
            "eave_height": "3",
            "ridge_height": "5",
            "u_value": "4",
            "inside_temp": "15",
            "outside_temp": "-5",
            "ach": "1"
        },
        "steps": [
            "Area = walls 2 × 39 × 3 = 234 m² + gables 9 × 2 = 18 m² + roof 2 × 30 × √(4.5² + 2²) = 295.47 m² → 547.47 m².",
            "Covering loss = 4 × 547.47 × 20 = 43.80 kW.",
            "Leakage = 1206 × 1080 × 1 × 20 ÷ 3600 = 7.24 kW; total 51.03 kW (174,133 BTU/h)."
        ],
        "result": "Holding 15 °C at −5 °C outside needs about 51 kW (174,000 BTU/h) of heat for this 30 × 9 m house."
    },
    "interpretation": "Choose a heater with output at or above the load (allowing for its efficiency), and consider a second skin or thermal screen to cut the covering loss.",
    "assumptions": [
        "Steady-state loss at the design temperature; no solar gain.",
        "The floor and soil heat exchange is ignored."
    ],
    "limitations": [
        "Wind, radiation to a clear night sky and thermal screens change the real load."
    ],
    "rules": null,
    "faqs": [
        {
            "question": "Why does the covering dominate?",
            "answer": "Glazing and films conduct heat far more readily than insulated walls, so area × U-value is usually most of the load."
        },
        {
            "question": "How do I convert kW to BTU/h?",
            "answer": "Multiply by 3,412.14."
        }
    ],
    "sources": [],
    "related": [
        {
            "name": "Greenhouse Ventilation Calculator",
            "url": "https://calculators.geekmidst.com/calculators/greenhouse-ventilation-calculator"
        },
        {
            "name": "Temperature Converter",
            "url": "https://calculators.geekmidst.com/calculators/temperature-converter"
        }
    ],
    "disclaimer": null,
    "publisher": "GM¹X CalcVerse"
}