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Here’s quite a pair: Geomembranes and butterflies

Products | October 1, 2007 | By:

New liner system installed in the Smithsonian’s Butterfly House


This immersive exhibit explores the processes and patterns of evolution, and provides visitors with a new kind of experience in the National Museum of Natural History (NMNH)—a walk-through living butterfly house.

NMNH will invite visitors to observe the many ways in which butterflies and other animals have evolved, adapted, and diversified together with their plant partners over tens of millions of years.

The specially constructed butterfly pavilion within the exhibit is a walk-though experience featuring hundreds of tropical butterflies in a climate-controlled environment, complete with flower planters and exit vestibules.

Geomembrane lining system

Installation of a technical geomembrane liner was completed this year during construction of the pavilion at the Smithsonian Institution’s Museum of Natural History Butterfly House in Washington, D.C. The membrane was specified in the construction plans in order to develop a series of planters in the pavilion’s enclosed tropical environment.

The new self-contained exhibit was built on the fourth floor of the NMNH. It offers a simulated natural environment that visitors can walk through and experience without barriers, numerous live, exotic butterfly species and even a pupator that will provide visitors the chance to see new butterflies emerging from their cocoons. The micro-climate necessary to support the various life forms in the Butterfly House incorporates precise temperature and humidity controls. One feature of the climate control system is a series of mist nozzles built into the walls of the structure. The high humidity and moisture provided by these mist nozzles required the installation of a geomembrane liner to contain the moisture within the structure and prevent it from harming anything outside of it.

The 45-mil reinforced polypropylene membrane was specified by engineers as a containment system and liquid barrier for the Butterfly House’s planters and flooring system.

The sensitive work in relatively close quarters included furnishing and installing the liner system, with heat and extrusion welding of all seams, attaching the liner to various structures, and performing field testing and quality control.Upon completion of the installation, the liner system was completely flooded as a final test for any previously undetected leaks.

The geomembrane-lined planter walls were finished with a rock facing treatment and the interiors covered with natural materials such as moss, lava rock and plantings to create a natural environment for the butterflies. The exhibit incorporates entrance and exit vestibules that create an air-lock effect to contain the butterflies within the exhibit. Curved semi-opaque exterior walls of the exhibit allow ample natural light to filter in from the museum’s adjacent exterior windows. The “greenhouse” style walls also incorporate two clear observation panels that allow visitors to view the exhibit without paying a walk-through fee. However, these same curved walls and curved planter structures further complicated the installation process as the membrane was cut and seamed to fit as tight as possible.

The project’s success will ultimately be determined by the performance of the lining system, as it will be protecting the floors of the museum beneath the new, enlarged Butterfly House.

The installation was completed by Hallaton Inc. of Towson, Md. Hallaton president, Todd Harman, said: “The Butterfly House project is very similar to the lining of a landfill or a petroleum tank farm, but instead of protecting groundwater from contamination, we are protecting the nation’s treasures from water damage.”

Charging for butterflies

In a rare move, the Smithsonian announced that it will charge an entry fee to patrons of the walk-through Butterfly Pavilion—an institutional first for a permanent exhibit.

The NMNH’s two-tier look at butterflies includes a general exhibition that will focus on the evolution of plants and butterflies. It will include a window looking into a special pavilion filled with live tropical butterflies. All that will be free. But visitors who want to enter the Butterfly Pavilion, a climate-controlled space with about 300 to 400 butterflies floating around, will have to pay a fee.

Butterfly pavilions are expensive ventures because the butterflies and plants have short life spans and need to be replaced frequently. The annual operating cost is estimated at about $900,000. Construction of the complete butterfly exhibition house and pavilion totaled about $3 million.

The butterfly pavilion was designed by Smithsonian staff members to create a hospitable environment for the insects. The butterflies will be drawn to light, with lamps substituting for natural light. It is not clear how long each visitor will stay, because the 1,400-ft2 pavilion will be heated to 80 degrees with 80% humidity. Staff members estimate that 30 people at a time will be able to visit the smaller pavilion area, and they predict 200,000 visitors a year.

The Smithsonian is using farms in Latin America, Africa, Asia, and North America to supply the butterfly pupae.

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