GAHT® System: Ground to Air Heat Transfer
A Ground to Air Heat Transfer (GAHT®) system, sometimes referred to as a ‘climate battery’, allows the greenhouse to provide its own heating and cooling using the energy of the sun and the soil underground. By utilizing this system, one is effectively able to create a geothermal greenhouse designed for renewable climate control and year-round growing, with a much lower environmental impact of a traditional HVAC system.
*The GAHT® system designed for a greenhouse is patented under US patent number US 11s006s586 B2.
Why Ground to Air Heat Transfer?
Our patented GAHT® system is a form of climate battery that provides year-round, energy-efficient climate control by utilizing the volume of soil under the footprint of the greenhouse as thermal mass to help regulate internal temperatures. Often called a ground to air heat exchanger, climate battery, or earth tubes, the system provides:
- Year round heating and cooling
- Air circulation
- Renewable climate control
Performance of the GAHT® System
How well the Ground to Air Heat Transfer (GAHT®) system functions will depend on:
- Locate climate
- Greenhouse construction
- Crop selection
The GAHT® system offers the best heating performance where there is sufficient sun in the winter time, the greenhouse is oriented towards the sun, and is well insulated.
Ceres Greenhouse Solutions is an industry leader in geothermal greenhouse ground to air heat exchanging technology, as we have designed and installed more systems than any company worldwide.
DO I NEED A GAHT® FOR MY GREENHOUSE?
A guide for whether to opt for this supplemental geothermal heating & cooling system.
Purchase Residential or Commercial GAHT® Plans
GAHT® System Greenhouse Plans
Design Package Includes:
Layout of GAHT® system for your chosen size
Materials list for all parts and sourcing information for necessary components
Step-by-step instructions, with pictures, explaining the underground install and how to install and wire the fans and thermostats
Price: $750 (Standard)
Commercial GAHT® Greenhouse System Design
Our Commercial GAHT® Services Include:
1 hour initial design consultation to learn growing goals and greenhouse design
Final layout depends on greenhouse configuration and floor plan
Customized design and layout of best possible configuration
Customized electrical layout and wiring diagrams, considering electric requirements, greenhouse design and electric supply
Finalized GAHT® system plans showing design and pipe layout
Materials list for final design
Unimitated phone support during installation
For commercial greenhouses, Ceres provides in-depth evaluation and engineering for your high-performance GAHT® system.
Price: Depends on project size and complexity
One centralized system for controlling the whole environment. Monitor temperature, relative humidity, and CO2, leaf/ canopy temp, PAR, lighting zones, and outdoor weather.
We offer Ceres designed EcoLoop™ or EcoPack™ HVAC options depending on growing goals, budget, site constraints, and greenhouse type. All Ceres environmental controls are custom integrated to suit your needs.
The GAHT® system is a ground to air heat exchanger, a system often referred to as a ‘Climate Battery’. Ceres leads the industry in climate battery technology, having designed and installed more systems in greenhouses than any other company in the world.
Different crops may demand specific lighting requirements. We offer a variety of lighting solutions designed to suit the needs of each individual operation.
A NetZero greenhouse will have zero net emissions. This goal is achieved through capturing and storing energy. This can be done using a various system options.
Ethylene tetrafluoroethylene is a durable, high light transmissive glazing option. It offers more than 95% light transmission, including the UV spectrum. More than other greenhouse companies, Ceres is implementing full spectrum glazings for maximum crop growth.
Access Greenhouse Technology Related Brochures
Calculate Your Energy Savings
Find out how much you can save with Ceres Greenhouses compared to standard greenhouses.
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GAHT® System FAQs
“Geothermal” is a broad term, meaning using heat from the earth. GAHT® systems do use the stable temperatures of the soil, however they are very different systems than geothermal heat pumps, often called “geothermal systems” for short. A geothermal heat pump incorporates a refrigeration cycle and circulates a fluid underground. They are much more complicated and expensive systems than GAHT® systems. GAHT® systems, in contrast, simply circulate air and bury pipes relatively shallow, up to 4’ underground.
Ceres Ground to Air Heat Transfer (GAHT®) system is a type of ground to air heat exchanger. Over the years, these have gone by many names including Climate Batteries, coined by Jerome Osentowski and Michael Thompson of the Central Rocky Mountain Permaculture Institute (CRMPI). GAHT® systems and Climate Batteries use the same concepts, with some slight differences in design and air flow rates. Another similar concept is earth tubes. These use one-way air flow: they draw air in run it underground and pump it into the structure. GAHT® systems, in contrast, are a closed loop.
The pipes of a GAHT® system have small perforations so as water condenses underground, it drains out into the soil. This also helps reduce mold issues, which have not been reported in years of testing.
Typically, pipes are buried up to 4’ underground. This can vary by area; the goal is to bury pipes deep enough to reach stable soil temperatures. We additionally insulate around the perimeter of the greenhouse to create an insulated pocket of soil beneath the structure.
In locations where the water table is higher than 4’, it is challenging to integrate a standard GAHT® system. Other heat storage methods, like phase change material can be used to make your greenhouse as energy-efficient as possible.
The cost of a GAHT® system depends on the size of your greenhouse. Typically, residential GAHT® systems (under 1,000 sq. ft.) cost between $2,000-5,000. Larger commercial greenhouses and school greenhouses typically cost $5,000-$15,000 depending on size.
To date we have never installed a house GAHT® system. This does not mean it is not possible. We just have not installed one. Before considering this option there are two concerns you should be aware of:
Radon can be tested. And even if there is radon, it is more significant to watch the rate at which it accumulates. In the worst case scenario, if radon is detected the GAHT® system can always be shut off.
According to studies that were performed by the University of Minnesota on several GAHT® systems where mold was tested no elevated spores were detected. It is important to keep in mind this is one study, and they were conducted on greenhouses and not homes.
When trying to mitigate mold in the home you could use a filtration system with a UV lamp. It is important to look at ducting system- how to get air through the system. We can help with the design of a new system, but it is harder to work with existing ones.
Understanding these precautions is necessary if you decide to try this system on a house. Please consult us if you are thinking of a house GAHT®.
Radon is a radioactive element that seeps into buildings through the soil. Since a GAHT® system circulates air directly through the soil, a common question is whether the GAHT® system adds a radon risk. In areas with high radon levels, this is a possibility and should be taken seriously. However, greenhouses are less dangerous than conventional buildings when it comes to radon. First, you are not in the greenhouse for as much time. Secondly, greenhouses have very high air exchange rates. During much of the year, air (and any radon) will be ventilated outside, and the whole structure will be flushed with fresh air in a matter of minutes. Even if the ventilation system is not on, greenhouses have many more air exchanges than a standard home, mitigating radon build-up. In our tests of GAHT® systems in the Rocky Mountains (an area with high radon levels), the concentration inside the greenhouse was found to be slightly higher than outdoors, but much lower than a dangerous level. By no means is this a comprehensive study, so if concerned, have your soils tested for radon before installing a GAHT® system.
In most cases both supplemental heating and dehumidification will be required for commercial greenhouses. This will depend on what climate you are in, the specifics of your greenhouse design, and what you plan to grow.