Heating Methods

There are multiple ways to heat a greenhouse; some methods working better than others depending on the type of application. Here you will learn about the benefits and drawbacks of each system. This information will help you select the heating system that best fits your needs. For additional assistance in selecting the best heating system for your particular application, feel free to contact your local product resource or click here to locate one.

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(NEW!) Separated Combustion, Tubular Heat Exchanger Unit Heaters

Fuel savings! Avoid highs costs of wasted heat due to open vents and high ventilation rates required with direct-fired and un-vented unit heaters.
Extend the life of your investment by keeping corrosive chemicals outside of the combustion chamber. When combined with an optional stainless steel heat exchanger, you can add years to your investment.
Create a safer environment for plant growth by venting all harmful combustion fumes outside.
Short heat recovery time reduces temperature fluctuations, promoting a natural growing environment.
Safeguard against mold and fungal diseases while delivering a gentle, uniform airflow.
Maintain uniform temperatures at bench or ground level, from wall to wall.
Installation of multiple multiple heaters builds redundancy and eliminates reliance on only one heater for your entire crop.
Versatility allows air to blow from the top of the greenhouse or through ducts.
Fan only operation may be used to circulate air in the warmer growing periods.
By using a fan to move the air, the heaters provide even heat throughout the entire greenhouse.
Modine gas-fired unit heaters maintain a minimum 80% efficiency.
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Vented Gas-Fired Unit Heaters

Short heat recovery time reduces temperature fluctuations, promoting a natural growing environment.
Provides air circulation to reduce dead spots in the greenhouse, reducing high moisture areas that promote mold growth.
By installing multiple heaters within the greenhouse you build in redundancy. If one unit would happen to go down, you still have others to maintain freeze protection which could save the entire crop.
Versatility allows air to blow from the top of the greenhouse or through ducts.
Fan only operation may be used to circulate air in the warmer growing periods.
Heaters are indirect fired, allowing all combustion products to be vented to the exterior of the greenhouse. Some plants are particularly sensitive to toxins found in the products of combustion.
By using a fan to move the air, the heaters provide even heat throughout the entire greenhouse.
Modine gas-fired unit heaters maintain a minimum 80% efficiency.

Unvented Direct-Fired Heaters

Discharges combustion products into the greenhouse, damaging crops and leading to serious discomfort, injury and/or death if not properly ventilated. These risks far outweigh any benefit that may be sought from CO2 being released in the combustion process.
Direct fired units, often advertised as 100% efficient, are in fact 92% efficient at most. The latent heat of vaporization consumes Btu's to maintain water vapor in its gaseous state, reducing efficiency to roughly 92%. Then, you must provide fresh air to meet safe air requirements. The energy required to heat this air can bring the overall system efficiency below 80%. And, the colder it gets, the less efficient the system is. Refer to unit heater efficiency for additional details.
Risk for increased condensation issues due to the water vapor produced from combustion. This vapor can condense within the greenhouse and cause mold and/or fungal diseases, as well as premature failure of metal objects (structures, conduit, wiring, etc).
Short heat recovery time reduces temperature fluctuations, promoting a natural growing environment.
Provides circulation to reduce dead spots in the greenhouse, reducing high moisture areas that promote mold.

Infrared

Claims that heat source is ‘like the sun’ are untrue because the sun provides light energy in wavelengths necessary for proper photosynthesis to occur. Infrared heat is of a different wavelength.
Infrared has uneven temperatures along the tube. The longer the tube, the greater the temperature differentiation, resulting in uneven plant growth.
Can only heat what it can see; therefore, obstructed plants will not get necessary heat.
Air becomes stagnant with lack of movement, leading to mold.
Tubes that heat plants on cold, sunless days actually block light during warm sunny days.
Recommended by loading docks and customer areas where the doors are constantly opening.

Duct Furnaces

Same benefits as gas-fired unit heaters but have a higher installed cost because of ductwork and the separate air mover.
Allows for higher static pressure from ductwork.
Can be mounted exterior of the space.
Have a larger variety of control options for make-up air.

Hydronic Under-The-Bench

Provides good soil heating.
Does not provide air movement, resulting in mold.
Reacts slowly when called upon to heat.

Hydronic Unit Heaters

Short heat recovery time reduces temperature fluctuations, promoting a natural growing environment.
Provides much needed air circulation to decrease dead spots in the greenhouse, reducing the high moisture areas that promote mold growth.
Usually supplied by one boiler which does not give you redundancy.
Fan may be used to circulate air in the warmer growing periods.
Don’t have products of combustion to be vented.

Hydronic In-floor Radiant

Reacts slowly when called upon to heat.
Usually requires unit heaters as part of the system.
Does not provide air movement