Greenhouse Heating Calculator
Estimate steady-state greenhouse heating demand from exposed area, insulation performance and temperature difference
This simplified estimate uses walls plus roof-plan area as exposed envelope area. Actual heat loss also depends on glazing, infiltration and greenhouse geometry.
Recommended heat output
How we calculated it
About the Greenhouse Heating Calculator
Greenhouse heating demand depends on the area of the enclosure, the temperature difference between inside and outside and how easily heat passes through the covering. Air leakage and wind can add further losses.
This calculator provides a planning heat-load estimate rather than a full HVAC design. Actual equipment sizing should consider local climate extremes, ventilation, thermal mass and heater performance.
How to Use the Greenhouse Heating Calculator
- Enter greenhouse dimensions or total exposed surface area.
- Enter the desired indoor temperature and design outdoor temperature.
- Choose or enter an appropriate heat-loss/U-value for the covering.
- Calculate heating load and add infiltration or design margin where the method supports it.
How the Calculation Works
Conductive heat loss is commonly estimated as Q = U×A×ΔT, where U is overall heat-transfer coefficient, A is envelope area and ΔT is the indoor-outdoor temperature difference.
Additional infiltration heat can be estimated separately from air-change rate and air properties. Total design load combines relevant losses rather than using floor area alone.
Worked example
Greenhouse Heating Calculator Worked Example
500 ft² envelope, U=1.2 BTU/h·ft²·°F and 30°F temperature difference
Conductive load = 1.2×500×30 = 18,000 BTU/h before air leakage, wind and design margin.
Result guide
Understanding Your Greenhouse Heating Calculator Result
The result is the heat rate required to offset modeled losses at the design condition. Mild weather will require less heat, while wind or leakage can increase demand.
Before you rely on the answer
Assumptions and Limitations
- Envelope area and U-value reasonably represent the greenhouse.
- Temperature difference reflects a realistic design condition.
- Solar gain is not relied upon unless explicitly modeled.
Practical tip
Using This Result in Practice
Use the coldest realistic design condition for heater sizing but avoid assuming every hour will be that cold. For fuel budgeting, seasonal energy modeling is more appropriate than multiplying peak load by all winter hours.
Related calculations
Useful Calculations to Continue With
If the greenhouse envelope area still needs to be calculated from several shapes, use the Area Calculator first.
If an electric heater’s power and operating hours are known, use the Electrical Energy Calculator to estimate energy consumption.
Common questions
Greenhouse Heating Calculator FAQ
Why is greenhouse heating based on surface area rather than floor area?
Most conductive heat escapes through the walls and roof, so exposed envelope area controls that loss.
What is U-value?
It represents heat transfer through a material or assembly; higher U-values mean more heat loss for the same area and temperature difference.
Does sunlight reduce heating demand?
During sunny periods it can, but a safe nighttime design should not depend on solar gain.