Heating a greenhouse can be quite expensive, especially during the cold winter months. When trying to find the most cost-effective heating method, greenhouse owners must consider factors like climate, greenhouse size, budget, and type of plants being grown. With some careful planning and research, there are affordable options to keep your greenhouse warm all year long.
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Types of Greenhouse Heating Systems
The main types of greenhouse heating systems include:
- Electric heaters – These use electric coils or fans to blow hot air through ductwork. Electric heaters can warm up quickly but running costs are higher.
- Propane heaters – Propane fuel is burned inside a chamber and the heat is distributed by fans. Propane is relatively affordable but units require ventilation.
- Natural gas heaters – Like propane heaters, these systems burn natural gas fuel to provide radiant heat. They are efficient and have lower operating costs.
- Geothermal heating – Underground pipes circulate water through the greenhouse which is warmed by the earth’s natural geothermal heat.
- Wood/pellet stoves – Stoves burn wood pellets or chips for radiant heat. Fuel costs can be low but regular loading/ash removal is needed.
When comparing heating system options, the main considerations are: upfront installation costs, ongoing fuel/electricity expenses, maintenance needs, greenhouse climate control capabilities, and safety.
Most Cost-Effective Heating Methods
Here are some of the most budget-friendly greenhouse heating solutions:
Passive Solar Heating
Passive solar heating takes advantage of natural sunlight to warm the greenhouse during the daytime. Greenhouse glazing materials like polycarbonate or fiberglass panels allow sunlight to enter and then trap the resulting heat inside the structure. Vents and shutters should be installed to regulate temperatures.
Benefits of passive solar heating include:
- Very low operating costs
- Renewable solar energy
- Lower carbon footprint
The main limitations are an inability to provide heat at night or during cold/overcast periods. Passive solar gain works best in milder climates as a supplementary heat source.
Rocket Mass Heaters
Rocket mass heaters are wood-burning systems that utilize a high-efficiency combustion unit for clean burning. A insulated thermal mass made of bricks or cob is installed alongside the burner to absorb and radiate heat over longer periods of time.
Benefits of rocket mass heaters include:
- Affordable materials like cob or clay
- Long burn times up to 24 hours
- Up to 90% efficient
- Can be DIY or professionally installed
Downsides are reliance on dry firewood supply, small heated area, and ventilation requirements. Rocket mass heaters are a low-cost option but work best paired with other heat sources.
Wood Stoves
Wood stoves that burn wood pellets, chips, or logs can be an economical heating choice depending on local fuel prices. These stoves use radiant heat and natural air circulation to warm greenhouses up to 300 square feet. Installing interior masonry around wood stoves boosts heat retention.
Benefits of wood stoves include:
- Affordable wood fuel prices
- Lower electricity costs
- Suitable for small to mid-sized greenhouses
Drawbacks are smoke, manual ash removal, and regular refueling. Proper installation with safety clearances is also crucial with wood stoves. Overall they can be a cost-effective primary or backup heating source.
Comparing Greenhouse Heating Costs
When evaluating the annual costs of different greenhouse heating systems, main factors to consider include:
- Fuel or electricity rates in your area
- Size of your greenhouse
- Your climate zone and seasons
- Type of greenhouse glazing material
- Heating system efficiency ratings
Here is a cost comparison table for heating a sample 30′ x 48′ greenhouse in USDA Zone 5b for one year:
| Heating System | Output BTUs | Annual Cost |
|---|---|---|
| Natural gas heater | 84,000 BTU | $1,500 |
| Propane gas heater | 60,000 BTU | $2,100 |
| Electric heater | 54,000 BTU | $2,400 |
| Wood pellet stove | 40,000 BTU | $950 |
As you can see, wood pellet and natural gas heating provide the most affordable options for a greenhouse of this size in Zone 5b. Geothermal and solar passive systems would also be less expensive to operate but have higher upfront installation costs.
DIY Low-Cost Heating Methods
For budget-friendly home greenhouse heating, here are some simple DIY solutions:
Water Containers
Large plastic jugs or containers filled with hot water can release gentle radiant heat as the water cools. The containers should be placed near plants overnight or on cold days only, removing them when temps increase.
Grow Lights
LED growing lights suspended over plants generate a surprising amount of warmth along with light for growth. Run times can be increased in winter to provide heat.
Thermal Curtains
Installing insulating curtains or plastic sheets along the interior walls helps retain heat overnight after the greenhouse warms up during the day.
Electric Space Heaters
A small electric space heater can take the chill off for a hobby greenhouse under 100 sq. ft. Use a unit with thermostat settings and safety auto shut-off.
Bed Warmers
Terracotta bed warmers filled with compost or sand can absorb heat during the day. Place these under seed trays or plants at night to provide gentle warmth.
While DIY heating options work for small hobby greenhouses, larger growing structures will benefit from more substantial heating systems for adequate climate control.
Conclusion
Finding affordable greenhouse heating solutions comes down to matching the system size and type to your climate, greenhouse specs, budget, and crops being grown. Wood stoves, propane, and natural gas offer the most cost-effective options for larger greenhouses. Smaller hobby greenhouses can utilize passive solar, grow lights, thermal curtains, and other DIY methods to provide low-cost supplemental heating.
Partnering passive solar gain with a backup propane or wood stove heater provides a balanced approach. The key is creating an efficient greenhouse structure with thermal mass to maximize heat retention. With some creative planning, you can keep your greenhouse warm through winter for an affordable cost.