Geothermal Greenhouse Calculator
Model the cold-night heating load for a greenhouse, then translate that demand into geothermal tonnage, loop footage, circulation flow, and thermal buffer volume using greenhouse-specific envelope and infiltration assumptions.
Choose a greenhouse profile or start from scratch. The calculator uses planning-grade assumptions for geothermal pre-sizing and reports both imperial and metric outputs.
| Glazing system | Approx. U-value | Night load band | Design note |
|---|---|---|---|
| Single poly film | 1.20 BTU/hr-ft2-F | 68-82 BTU/hr per sq ft | Fast payback for spring houses, but loop fields grow quickly in true winter duty. |
| Double poly film | 0.70 BTU/hr-ft2-F | 52-66 BTU/hr per sq ft | Common all-round baseline for year-round hobby and commercial greenhouse sizing. |
| 8 mm twin-wall polycarbonate | 0.58 BTU/hr-ft2-F | 46-60 BTU/hr per sq ft | Useful in windy sites where lower infiltration and lower U-value both matter. |
| Double glazed greenhouse glass | 0.62 BTU/hr-ft2-F | 48-62 BTU/hr per sq ft | Higher solar transmission than many plastics, but framing thermal bridges still matter. |
| Insulated north wall mix | 0.50 BTU/hr-ft2-F | 42-56 BTU/hr per sq ft | Pairs well with slab or root-zone delivery where one orientation can be opaque. |
| High-performance glass / triple-wall | 0.42-0.45 BTU/hr-ft2-F | 40-54 BTU/hr per sq ft | Best when precision climate control justifies tighter envelope targets and higher upfront detail. |
Night load bands assume average greenhouse air change control and crop temperatures between 56 and 66°F.
| Crop profile | Typical night target | Humidity impact | Best delivery fit |
|---|---|---|---|
| Seedlings / propagation | 64-68°F | High moisture, strong latent reserve | Root-zone loops or hybrid slab plus air |
| Leafy greens | 54-58°F | Moderate moisture, lower air temp okay | Bench hydronic or low-temp slab |
| Tomatoes / peppers | 60-64°F | Balanced sensible and latent demand | Hybrid emitters for night setback recovery |
| Cut flowers | 58-62°F | Consistent RH target during dark hours | Radiant slab with trim air movement |
| Orchids / tropical foliage | 66-70°F | High humidity reserve and tighter shell | Vertical loop plus bench or root-zone heat |
| Loop type | Field footprint | Soil sensitivity | Greenhouse use case |
|---|---|---|---|
| Horizontal trench | High | Medium to high | Best for hobby houses, high tunnels, and broad sites with easy excavation. |
| Vertical boreholes | Low | Low to medium | Useful where greenhouse land is precious or paved support areas surround the structure. |
| Slinky trench | Medium | Medium | Fits retrofits that cannot spare full horizontal trench length but still allow excavation. |
| Pond loop | Very low on land | Low if deep water exists | Excellent for aquaponic greenhouses and rural sites with a suitable water body. |
| Energy baskets | Very low | High | Compact solution for small structures where moisture-rich soil and careful header design are available. |
| Project | Footprint | Typical geo size | Best loop fit |
|---|---|---|---|
| Backyard hoop house | 12 x 24 ft | 1.5-2.0 tons | Horizontal or baskets |
| Four-season herbs | 20 x 40 ft | 2.5-3.5 tons | Basket or vertical if site is tight |
| Flower range | 24 x 60 ft | 4.0-5.5 tons | Vertical or slinky trench |
| Commercial tomato house | 30 x 96 ft | 6.0-8.5 tons | Slinky, vertical, or pond loop |
| Propagation complex | 30 x 72 ft | 5.0-7.0 tons | Vertical or hybrid field |
Greenhouses often see large daytime solar gains, but geothermal field length is usually set by the coldest dark-hour load. Size with the true winter night temperature, not midday averages.
If curtain performance improves from none to double layer, the required geothermal field may shrink more than switching from one loop layout to another on the same site.
Bench hydronic, slabs, and root-zone circuits usually var the heat pump run cooler supply water than unit heaters, which supports better compressor efficiency and steadier crop comfort.
Moist loam, clay, or shoreline soils reject and absorb heat better than dry fill. If field conditions are uncertain, keep the design buffer or confirm conductivity before trenching.
The right size of heater for greenhouse depends on two main things. It relates to the size of the greenhouse and to the need of heat. For small greenhouse a smaller heater is enough.
Big greenhouses require stronger heaters. A calculator for heating of greenhouse helps to go through that step. It points what size electrical, natural gas or propane heaters you must choose for a kit.
How to choose the right heater size for your greenhouse
That tool help with warming, cooling and control of moisture.
Geothermal heater calculator estimates how much heat you require to keep the wanted temperature. This is main spot because first comes calculation of heating. You can compile needs for warming by BTU, size of heater and estimated costs.
They base on size and insulation. Any calculator uses past weather for a place to find degrees of warming and cooling. It takes also size and data about covering of tunnel to set size of heater, use of fuel, needs for cooling and first cost of it.
There exists also utility for simulate heaters and use of energy what lowers costs for warming.
Heat pump is needed because usual heating for greenhouse requires heat that is high. Now gears work well at a lower price than some years ago. When you want heat at low temperature such as for keep air a bit above freezing you can use it directly.
Most geothermal systems pay itself in less than ten years if energy prices reach $25/MBtu. Some cases give even better result between 3 and 7 years. That depends of geothermal source cost of system and amount of fossil fuels removed.
When prices of fossil fuels grow return for alternative heating systems become faster.
Geothermal system draws heat from the soil. It regularly gives difference of 35 until 40°F between air entering the ground and exiting. The space receives heat of huge crowd of sunradiata heat stored in the ground under greenhouse.
Fans enter cool overnight air through a tube net to add heat and humidity back into the greenhouse. The soil keeps almost permanent temperature already in 8 feet under surface. For estimate greenhouse and geothermal system you can use on-line calculator for climate.
