wofati greenhouse Q&A

Kickstarter and Project Plans

• The Wofati greenhouse Kickstarter reached its funding goal within about three hours and was described as more than triple-funded at the time of the livestream. The team had recently announced stretch goals.
• The greenhouse is intended as an experimental build. The team hopes to test a combination of solar gain, earthen thermal mass, air movement, and graywater treatment rather than rely on a single heating system.
• If additional funding allows, the project might expand the greenhouse and add more test wells and air pipes. A separate, more ambitious idea is a Wofati freezer.

Greenhouse Design and Thermal Approach

The proposed greenhouse would use sunlight to warm its growing space and thermal mass, which is intended to moderate temperature swings. The team hopes the interior might stay around 65°F on the coldest days and 85°F on the hottest, but emphasized that this is a goal to test, not a proven result.

The team’s broader Wofati concept uses annualized thermal inertia: storing warmth in the ground during warmer periods and drawing on it during colder periods. They expect it may take three to five years for the ground mass to settle into a stable annual pattern.

The greenhouse is being designed around the site’s terrain, though its chosen location is only moderately sloped and may need to be built up. The speakers noted that Wofati designs usually benefit from a slope.

An existing Wofati structure, Allerton Abbey, was intended to test thermal mass without passive-solar gain. Early observations were suggestive but not conclusive: the mass had not been fully charged, and the building reached about 39°F during a period when the team was away.

The greenhouse’s growing area is modest and still subject to design changes. Figures mentioned included roughly 10 by 3.5 feet for a rear growing area and about 3 by 6 feet near the front windows; the exact dimensions were not settled.

Proposed Thermal Trench and Pipes

The current plan was described approximately as follows:

1. Make a walking trench about 3 feet deep, with a deeper trench below it about 5 feet deep.
2. Place vertical well casings at the bottom of the deeper trench. The planned casings are about 6 inches in diameter and 20 feet long, for a total depth of roughly 28 feet from ground level.
3. Install air-stratification pipes to encourage air exchange with the deeper, cooler or warmer ground. The initial plan included a 1-inch pipe, with larger or additional sizes potentially tested if funding permits.
4. Compare pipe configurations experimentally. The speakers debated whether larger pipes would improve airflow or instead encourage internal circulation that could reduce the desired draw from the bottom of the pipe.
5. Consider a branched pipe arrangement if the initial pipe design does not create enough airflow. This was an idea raised during the discussion, not a finalized design.

The speakers stressed that these choices remain experimental and that they do not yet know which arrangement will work best.

Graywater System

The greenhouse is also meant to process household graywater, with a target capacity of roughly 30–50 gallons per day. The system is intended to operate by gravity, without a pump, and remain passive throughout.

One option is a constructed wetland using plants such as reeds, rushes, cattails, and grasses. In that design, plant roots are exposed to the water, and root activity helps support oxygen-rich biological treatment. Another possibility is a mulch-basin-style system, which would allow plants suited to ordinary soil rather than plants that tolerate inundated roots.

As a rough planning guideline for a constructed wetland, the speakers cited about one square foot of growing area per gallon of daily graywater flow. They planned to consult graywater designer Art Ludwig before settling on a design.

The team emphasized that this is a small, experimental system. If it receives a temporary surge beyond its intended capacity, some final treatment might occur in soil outside the greenhouse.

Passive Design and Alternatives

The team’s stated goal is a system that does not depend on electricity, wood heat, mechanical equipment, or continual human intervention.

They contrasted that goal with compost-heated greenhouses based on Jean Pain’s method. In their view, such systems can produce useful heat but are not fully passive because the compost pile must be rebuilt periodically.

They also discussed a greenhouse approach that uses a fan to move air through buried tubing. They regarded it as a useful, low-energy technique, but not a truly passive one.

A possible passive air-to-air heat exchanger was sketched out: a darkened pipe divided by a metal plate, with separate air paths for incoming and outgoing air. Solar heating could drive airflow and transfer heat between the streams. The speakers also considered how to manage condensation, potentially routing it into the graywater system or soil. This remained a concept rather than a confirmed feature.

Freezer Concept

The proposed Wofati freezer would be a separate structure, sunk into the ground on a north-facing slope, with no windows and a single opening on the uphill side.

The idea is to use cold air and the ground’s thermal conditions to help keep stored food frozen, potentially allowing a fall harvest to remain frozen through summer. The team was unsure whether it could make ice or only preserve already-frozen items.

A “passive cold pump” was discussed as a way to move heat out of the freezer, but the speakers repeatedly noted that its effectiveness would need to be tested.

Climate and Testing

The team discussed possible suitability for different climates, including Tennessee, but said the design would need to be adapted to local conditions. They thought the approach would be less suitable for the Gulf Coast of Texas, where winters are mild and temperature swings are small.

They also noted uncertainty about local climate-zone classifications in Montana, citing estimates ranging from Zone 4 to Zone 5.

The central lesson was that these designs involve many interacting features. The greenhouse may show whether the combined system works, but it will be difficult to isolate the contribution of each individual improvement. Experiments and variations by future builders may help build that understanding.

Speakers and Sources Featured

• Paul Wheaton — Main presenter and host of the Q&A.
• Kyle — Participated in the discussion and was identified as the greenhouse designer; the exact full name is unclear from the subtitles.
• Jake — Mentioned in connection with a question about ventilation and overheating; it is unclear whether he spoke directly.
• Vention — A participant whose comments and questions were read or discussed.
• Eleonora Justice — Viewer whose question about the freezer was read aloud.
• Shawn and Jim — Viewer names mentioned in connection with questions or comments.
• Art Ludwig — Graywater design expert the team planned to consult; his book Creating an Oasis with Greywater was referenced.
• Mike Aylor — Discussed in relation to pipe sizing.
• Jean Pain — Referenced as the source of a compost-heating approach.
• Don Stephens — Referenced for earlier experiments and the annualized geo-solar approach.
• Jack Spirko — Mentioned in connection with an interview and an expert-council segment.
• Fred and Josiah — Mentioned as members of the project team; Fred was expected to help guide the build, and Josiah to lead it.