Natural gas heaters are a common choice for greenhouse heating thanks to reliable output and fuel availability. Below is a concise comparison of five suitable units for greenhouse environments, selected for coverage, BTU output, and mounting/venting options.
| Product | Type | Max BTU | Coverage |
|---|---|---|---|
| Dyna-Glo IR30NMDG-1 | Infrared Wall Heater | 30,000 | Up To ~1,000 sq. ft. |
| Mr. Heater Big Maxx MHU80NG | Unit/Forced Air Heater | 80,000 | Up To ~2,000 sq. ft. |
| ProCom MN300TPA-B | Ventless Infrared | 30,000 | Up To ~1,400 sq. ft. |
| ProCom MN300TBA-B | Ventless Blue Flame | 30,000 | Up To ~1,400 sq. ft. |
| Comfort Glow 17,000 BTU Direct Vent | Direct Vent Wall Heater | 17,000 | Up To ~570 sq. ft. |
Dyna-Glo IR30NMDG-1 30,000 BTU Infrared Wall Heater
Type: Infrared wall-mounted heater designed to radiate heat directly to surfaces and objects rather than just heating air.
Key Features: Natural gas ready (no conversion allowed), infrared heating that warms objects and people, up to 30,000 BTU, rated coverage up to approximately 1,000 sq. ft.
This heater uses infrared technology to deliver heat that is felt quickly at target areas, which can be beneficial in greenhouses where plants and benches absorb radiant heat. Wall mounting saves floor space and positions radiant panels to warm plant zones. The model is specified for natural gas without fuel conversion, so confirm gas supply type before selecting.
Mr. Heater F260560 Big Maxx MHU80NG 80,000 BTU Unit Heater
Type: High-output natural gas unit heater intended for larger spaces and forced-air distribution.
Key Features: 80,000 BTU, coverage up to ~2,000 sq. ft., includes angle brackets and LP conversion kit, requires venting options (category 1 vertical or category 3 horizontal), electrical connection for fan and controls.
This unit is a forced-air heater suitable for larger greenhouses or areas requiring faster air temperature control. The fan-driven design circulates warmed air, which helps reduce cold pockets but may increase humidity redistribution. Review clearance and venting requirements carefully; installation typically requires experienced HVAC or licensed contractor work and attention to combustion air for greenhouse enclosures.
ProCom MN300TPA-B Ventless Natural Gas Infrared Space Heater
Type: Ventless infrared heater with thermostat control for indoor residential use.
Key Features: 30,000 BTU, heats up to 1,400 sq. ft., thermostat with High/Medium/Low settings, slim profile for wall mounting or floor placement, includes wall mount and base feet.
As a ventless infrared heater, this model delivers radiant heat without a flue, which increases indoor heat efficiency but releases combustion byproducts into the greenhouse air. The thermostat control helps maintain setpoints. For greenhouse use, ensure adequate ventilation and monitoring of CO and oxygen levels when using ventless appliances where plant respiration and human presence coexist.
ProCom MN300TBA-B Ventless Natural Gas Blue Flame Space Heater
Type: Ventless blue flame heater that heats air and surfaces with visible flame-based convection.
Key Features: 30,000 BTU, heats up to 1,400 sq. ft., thermostat control with multiple heat settings, slim design for wall or floor placement, includes base feet and wall mount.
The blue flame design produces a convective warmth that mixes with greenhouse air, offering even heat distribution for multiple plant benches. Ventless operation means no flue, but also direct combustion products are present in the space. An integrated thermostat and multi-setting control provide basic automation for temperature stability. Consider indoor air quality safeguards and local codes for ventless appliances in greenhouse applications.
Comfort Glow 17,000 BTU Direct Vent Natural Gas Wall Heater
Type: Direct vent wall-mounted heater with sealed combustion chamber.
Key Features: 17,000 BTU, heats up to ~570 sq. ft., sealed burn system with matchless piezo ignition, safety pilot and built-in pressure regulator, compact wall-mount design.
This direct vent model isolates combustion from greenhouse air by routing intake and exhaust through a vent, improving indoor air quality for both plants and people. Lower BTU output suits smaller greenhouses, propagation rooms, or supplemental heating near sensitive seedlings. Direct venting increases installation complexity relative to ventless units but provides better combustion safety and fewer emissions inside the structure.
Buying Guide: Choosing The Right Natural Gas Greenhouse Heater
Selecting the appropriate greenhouse heater involves balancing heat output, air quality, efficiency, installation complexity, and plant–human safety. The sections below break down the key considerations and comparisons.
1. Heater Type And Heat Distribution
- Radiant/Infrared Heaters: Heat objects and plant surfaces directly, useful for spot heating benches and reducing heat loss through circulation. Infrared can reduce cold leaf stress during night-time drops.
- Forced-Air/Unit Heaters: Use fans to move warm air and are effective for whole-house/large greenhouse heating. They create more uniform air temps but can disturb humidity layers and increase air movement.
- Blue Flame/Convective Heaters: Mix warm air into the space, offering even heating for bench arrays. Ventless blue flame units warm air quickly but introduce combustion byproducts indoors.
- Direct Vent Heaters: Provide sealed combustion and exhaust, preferred where indoor air quality and CO/O2 control are priorities.
2. Output (BTU) And Space Sizing
- Match BTU capacity to greenhouse volume and insulation. Typical guidelines: small propagation tents may need 10k–20k BTU, medium greenhouses 20k–60k BTU, large commercial spaces 60k+ BTU depending on insulation and climate.
- Account for extreme cold days and desired nighttime setpoint. Always use a safety margin rather than running at maximum capacity continuously.
3. Venting And Indoor Air Quality
- Ventless heaters are efficient but introduce combustion products (CO2, water vapor, other gases) into the greenhouse. This can increase CO2 beneficially for plants but requires careful oxygen monitoring and adherence to safety codes.
- Direct vent or flued units keep combustion gases out of the space and are preferable when enclosed spaces house workers frequently or sensitive plant stages.
4. Thermostat, Controls, And Automation
- Digital thermostats, programmable controls, and safety sensors (odors, oxygen depletion, CO) enable precise climate control and help avoid overheating or unsafe combustion conditions.
- Consider integration with greenhouse controllers that manage heating, ventilation, and humidity together to maintain balanced microclimates.
5. Installation, Clearance, And Code Compliance
- Check manufacturer clearance requirements, venting categories, and local building/gas codes before purchase.
- Professional installation is often required for high-BTU unit heaters and direct-vent systems to ensure safe combustion air supply and proper exhaust routing.
6. Humidity And Condensation Effects
- Gas heaters produce water vapor through combustion, especially ventless models; this can raise greenhouse humidity and increase condensation risk. Pair heating with ventilation or dehumidification strategies as needed.
7. Safety Features To Prioritize
- Oxygen Depletion Sensors (ODS) or automatic shut-off for ventless units
- Sealed combustion for direct vent models
- Overheat protection and tip-over or mounting safety where applicable
8. Maintenance And Fuel Considerations
- Plan for annual inspection of burners, pilots, vents, and gas lines. Clean radiant surfaces for efficiency.
- Confirm natural gas pressure and supply capacity for chosen BTU load; multiple heaters may require dedicated gas lines or regulators.
9. Comparison Perspectives
- Energy Efficiency vs. Air Quality: Ventless units are efficient but affect air quality; direct vent sacrifices some efficiency for cleaner greenhouse air.
- Spot Heating vs. Whole-Structure Warming: Infrared/radiant units are effective for bench-level spot heating, while forced-air units suit full-structure temperature control.
- Initial Cost vs. Long-Term Operation: Higher-capacity or vented models often cost more to install but can reduce long-term ventilation and health risks.
When selecting, weigh the greenhouse size, insulation level, crop sensitivity, local codes, and whether people regularly occupy the space. For larger or commercial greenhouses, consult HVAC professionals to size and design a safe, code-compliant heating system.