Tropical Forest Conservatory

A total rethinking of greenhouse technology, from earth tubes and fuel cells to computer-driven ventilation and shading.

The Most Energy Efficient Conservatory in the World

Truth be told, Phipps did not originally set out to build the most energy efficient conservatory in a public garden in the world. Construction documents were already complete for the new Tropical Forest Conservatory. But a funny thing happened on the way to the jungle—Phipps turned "green."

The success of the Silver LEED certified Welcome Center inspired Phipps to rethink its next project. Could they apply what they learned and question all conventional design assumptions that defined conservatory construction since the 1840s?

A Revolutionary Approach to Heating & Cooling

Eliminating many of the high costs associated with supplemental heating and cooling was top priority. Phipps started with a question: "What would happen if the design didn't follow conventional roof venting with a single high and low vent and instead had every other row of glass on the roof open?"

Conventional conservatory design is based on the chimney effect to maximize passive cooling or it relies on massive fans to force air exchange in the building. By completing a computational fluid dynamic study, Phipps confirmed that mechanical ventilation and cooling of the building could be eliminated and that 100% passive cooling would be sufficient for visitor comfort and plant performance with the new vent design.

The next concern had to do with conserving heat to minimize energy consumption in the winter. Historic Review Commission concerns led the architects to design a Tropical Forest building with a high south wall and a roof that sloped downwards from south to north.

Originally, Phipps specified single pane glass for the whole building. While double pane insulated glass reduces heat loss, it blocks too much light for plant performance. The architect did a winter sun tracking study, which showed that almost all of the direct winter sun enters through the south-facing wall, not the roof. What if Phipps left the south wall as single pane glass, but changed the roof glass (where most heat is lost) to insulated double pane? Engineers estimated that the double pane insulated roof glass would save 1,526 million BTUs annually.

Tropical Forests Innovations At a Glance

• Unconventional building shape allows use of energy-saving insulated roof glass while still maintaining proper light levels for growing plants.
• Radical roof venting system, coupled with earth tubes, fogging and computer controlled thermal blankets, make the structure 100% passively cooled.
• A solid oxide fuel cell, manufactured by Siemens Power Generation, converts natural gas into electricity with remarkable efficiency. It is the world's first use of a fuel cell in a public garden.
• Root-zone heating and thermal massing in the surrounding walls amplify energy savings.
• Excess heat generated by fuel cell provides tempered water for the reverse osmosis system and for watering the tropical plants.
• Special Events Hall adjacent to the Conservatory features Solarban 70 XL solar control low-emissivity glass, the most energy-efficient glass made, designed and manufactured by PPG Industries, Inc. Phipps represents the first commercial installation of this glass.

The final result? The most energy efficient conservatory in a public garden in the world. Cooling costs are practically zero; heating costs are estimated to be $2,400 per annum. This can be compared to $16,800 that would be used to heat a traditional conservatory of the same size.