Growing conditions
Heating a greenhouse through winter
A cold-night heat estimate helps you plan the project without pretending to size an HVAC system.
Short answer
Heating demand rises with exposed envelope, temperature difference, glazing losses, and air leakage. Use the Finder estimate as a planning range, then confirm equipment, fuel, electrical service, clearances, controls, and installation with qualified professionals.
What the estimate includes
The Finder combines exposed envelope conduction with an infiltration range using the selected greenhouse dimensions, glazing evidence, target temperature, and a location-specific design-cold temperature when one is available. Foundation/perimeter loss is shown as unresolved when the catalog cannot support it.
Why it is a range
Glazing construction, door and vent leakage, wind exposure, foundation details, thermal curtains, and the actual cold-night design condition can move the result. A rounded BTU/hr range is more honest than an exact number.
What remains to confirm
Choose equipment only after the load is understood. A qualified installer should confirm heater suitability, combustion venting, electrical/fuel service, clearances, controls, freeze protection, and what happens during a power outage.
Common mistakes
- Using the record low as the design temperature.
- Treating average winter temperature as a heat-load input.
- Sizing from footprint alone.
- Assuming a plug-in heater or an accessory listing proves greenhouse suitability.
A judgment call
Use the estimate to understand project scale and ask better questions. It is not a guarantee of indoor temperature or a replacement for local installation advice.