The National Aviary’s Wetlands habitat is a jewel box of bird conservation, an immense mid-century structure covered in more than 1,200 panes of glass. Now, thanks to recent renovations, the Wetlands shines more brightly than ever. In 2022 the habitat was stripped to its bones and re-clad with brand-new glazing. Starphire Ultra-Clear® acid-etched glass improves daylighting, prevents bird strikes, and presents visitors with a breathtaking vision of this legacy bird conservatory in all its glory.

Our thanks to James Smith of Montgomery Smith Inc., and Conor McGarvey and Molly Toth of the National Aviary for their help in writing this article.

A modern greenhouse

Constructed in 1969, the National Aviary Wetlands habitat is an unusual mixture. According to glasshouse consultant James Smith of Montgomery-Smith, Inc., “It’s not a typical conservatory. It’s more of a mid-century modern design with full curtain wall systems, not lapped glazing. So it’s a very different building than we typically consider a conservatory or a greenhouse exhibit space, and that posed challenges due to the construction.” This modernist design, and the material choices from the original construction, had some unexpected implications for the building as it aged.

Acid-Etched Glass Improves Daylighting at the National Aviary Wetlands Habitat

The National Aviary Wetlands habitat during its initial construction in 1968/69.
Image credit: Allegheny Conference on Community Development, Detre Library & Archives Division, Senator John Henry Heinz History Center Pittsburgh, PA.

Acid-Etched Glass Improves Daylighting at the National Aviary Wetlands Habitat

Guests inside the Wetlands shortly after it opened in 1969.
Image credit: Allegheny Conference on Community Development, Detre Library & Archives Division, Senator John Henry Heinz History Center Pittsburgh, PA.

Good intentions, mixed results

As James Smith mentioned, the Wetlands’ shell uses a full curtain wall glazing system instead of the lapped glass approach more common in traditional greenhouses. Whereas lapped glass allows some air exchange through the unsealed lap and encourages airflow through passive ventilation, the airtight curtain walls of the Wetlands building held the habitat’s warm, moist air in place, which caused the metal hardware and other components to degrade over time.

Overhead, the building had other challenges from the original design. The roof was covered with frosted glass panels with the textured surface facing the inside of the building. This was meant to accomplish three things: to increase visible light transmittance, to diffuse sunlight so it wouldn’t burn the plants inside, and to minimize condensation runoff from the inside surface of the glass. The first two goals were straightforward enough. However, positioning the rough surface toward the building’s interior and giving minimal slope to the glass had unintended consequences.

The rough surface was meant to catch water from condensation on the sloped ceiling tiles, preventing droplets from “raining” down inside the habitat. It worked a little too well. The glass caught and retained moisture, which caught and retained dirt particles, which reduced light flow into the space. Furthermore, the constant moisture caused hardware in the roof to age more quickly than it would have in a dry setting. This led to leaks and breaks, to the point where the National Aviary had to install a layer of plastic underneath the original roof. Of course, this extra layer reduced daylighting in the interior even more.

By the time of renovations, according to Smith, natural daylighting in the Wetlands was down to around 45% visible light transmittance (VLT). It was a far cry from the 80% VLT they were aiming for. Higher light transmittance would boost plant growth and make the Wetlands a much more pleasant space for birds and visitors.

Restoring this mid-century structure was going to take a lot of problem-solving.

Levelling up: daylighting, bird-safe glass, and privacy

James Smith and the Aviary staff got creative. They had experience working with Walker Glass material in earlier projects; Montgomery-Smith had used Walker Textures® Velour etch on Starphire Ultra-Clear® glass to improve daylighting at the Aviary’s Tropical Rainforest habitat in 2018. Conor McGarvey, the National Aviary’s Director of Facility Development and Operations, had overseen the construction of The Garden Room, whose windows deter bird strikes while delivering great views through AviProtek® bird-friendly custom pattern. This was an experienced team who knew what they were doing. This time around, they came to the project with an ambitious mix of goals for the glass:

  • To increase VLT and improve daylighting for birds, plants and people;
  • To ensure longevity – no one was in any hurry to go through the restoration process a second time!
  • To deter bird strikes from inside and outside the building;
  • To give visitors a view of the surrounding trees and sky;
  • To hide the exhibit’s nuts and bolts. Even the most luxuriously designed space has its workaday parts, and the team wanted to maintain visitors’ sense of wonder by keeping these parts out of visitors’ view.

Seeing the light through low-iron acid-etched glass

To increase light transmittance, James Smith of Montgomery-Smith Inc. went right back to the basics of material selection. For the roof, in place of the old clear glass panes with a frosted interior surface, he chose Walker Textures® full surface acid-glass with a Velour finish on position 1 (exterior). This way, the space would still reap the daylighting benefits of etched glass but the inside surface would shed its condensation more easily, leading to better longevity with less accumulation of dirt and grit (more on that later).

The glass substrate itself is 3mm Starphire Ultra-Clear® glass from Vitro Glass, which transmits daylight significantly better than regular “clear” glass. Combined with a light-scattering Velour etch, this glazing material transmits approximately 89% of visible daylight – nearly double the light transmittance of the old roof!

The Glass

The National Aviary’s Wetlands habitat uses a combination of Walker Textures® full-surface Velour acid-etched glass and AviProtek® bird-friendly pattern 214, all on a base of Starphire Ultra-Clear® glass from Vitro.

Roof and lower sidewall: two layers of 3mm Starphire Ultra-Clear® glass with Walker Textures® Velour finish on surface 1 and an N-UV interlayer.

Sidewall rows 3 and 4: two layers of 3mm Starphire Ultra-Clear® glass with AviProtek® pattern 214 on surface 1 and an N-UV interlayer.

Upper sidewall: Monolithic 5mm Starphire Ultra-Clear® glass with AviProtek® pattern 214 on surface 1.

Every project comes with its own unique criteria that require different solutions. The Wetlands habitat involved several different glass compositions, all developed with the help of glass samples. Walker Glass samples are available by request, in Walker Textures® or AviProtek® sample boxes, or as custom 12” squares. Let us know what you need, and we’ll provide solutions.


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Of course, the acid-etched glass improves daylighting in other ways as well. The etched surface scatters light particles, diffusing them throughout the building’s interior. This reduces harsh sunlight and glare, protecting plants from sunburn (yes, plants can be sunburned) while ensuring that daylight reached the furthest depths of the habitat. The result: an environment filled with soft, diffused daylight.

If you’re interested in daylighting in architecture, you may enjoy our recent blog post on Lisa Heschong’s Seven golden rules for great daylighting in architecture. The article consolidates advice from one of the industry’s leading experts in natural daylight, straight from the horse’s mouth.

Glazing goal: increase VLT and improve daylighting for birds, plants and people – success!

Acid-Etched Glass Improves Daylighting at the National Aviary Wetlands Habitat

Diffused daylight fills the newly renovated Wetlands habitat.
Photo by
Jim Cunningham Photography, courtesy of the National Aviary.

Building to last

The original curtain wall system used in the Wetlands building incorporated good ideas, but it wasn’t perfectly adapted to the warm, wet environment of this habitat. To ensure that the new glazing system would outlive its predecessor, the teams at Montgomery-Smith and the National Aviary made some key changes.

One deceptively simple improvement was to etch the exterior surface of the roof glass and leave the interior face unetched. A smooth interior surface means the glass holds far less moisture and lets the condensation “run” down the slope better than the original frosted panes. A dry ceiling means a longer lifespan for the metal frame and joints, with the added advantage of gathering less dirt over time. That’s a big perk, as anyone who’s cleaned a greenhouse will agree.

What about condensation raining down? You may recall that reducing interior “rain” was one reason for having a textured ceiling in the first place. The restored roof addresses the issue with condensation gutters at the lower end of the glass panels. Problem solved!

Glazing goal: build for longevity – success!

Bird-friendly, inside and out

As one of the nation’s leading bird conservatories, the National Aviary is committed to protecting bird life in and around its habitats. Part of this responsibility is preventing bird strikes against its buildings’ windows. The Aviary had seen great success with its previous bird-friendly glazing projects – The Garden Room and the Tropical Rainforest – and the team wanted similar bird deterrence for the restored Wetlands habitat.

Montgomery-Smith and the Aviary team selected AviProtek® bird-deterrent pattern 214 for the Wetlands walls. It’s a nature-inspired design of gentle curves winding back and forth, reminiscent of tall grass or cattails. Pattern markers are spaced closely enough to meet the 2×4 rule for bird-safe glazing, yet far enough apart to offer clear views of the outdoors. The team chose pattern 214 for this project because it reminded them of the leafy plants and grasses that flourish in natural wetlands environments.

Acid-Etched Glass Improves Daylighting at the National Aviary Wetlands Habitat
The renovated Wetlands habitat’s curtain walls are safe for local birds, thanks to AviProtek® bird-friendly pattern 214 on surface 1. Photo by Jim Cunningham Photography, courtesy of the National Aviary.

Positioned on the outer surface of the glass, the pattern prevents bird strikes from inside and outside the building. From the outside, wild birds can see the markers in any weather conditions, even when sunlight reflects off the glass. From the inside reflections are less of a concern, since light is almost always brighter outdoors than indoors. Thus, these exterior-surface markers are the best choice for bird-deterrent glass.

Glazing goal: deter bird strikes while giving visitors a view – success!

Glaziers installing panels of AviProtek bird friendly glass

Installing AviProtek® bird-friendly glass in the Wetlands habitat curtain walls by the craftsmen of Greenhouse Renovation Services, Inc.
Photo by
Jim Cunningham Photography, courtesy of the National Aviary.

Keeping some mystery

The National Aviary’s habitats present immersive wildlife experiences, but they’re also working buildings. Behind the polished public face of each exhibit, there’s a myriad of air exchangers, humidity control, structural support, and other nuts-and-bolts pieces that keep the whole system working smoothly. At the Wetlands, those details are concealed behind Walker Textures® full-surface acid-etched glass with a Velour finish. These panels use the same low-iron substrate as the bird-friendly windows in the upper part of the curtain wall, so they harmonize perfectly with the rest of the building.

Glazing goal: hide the nuts and bolts – success!

Acid-Etched Glass Improves Daylighting at the National Aviary Wetlands
Walker Textures® full-surface acid-etched glass in the curtain wall’s lower panels keeps the Wetlands’ machinery discreetly hidden. Photo by Jim Cunningham Photography, courtesy of the National Aviary.

The big reveal – the Wetlands habitat with new acid-etched glass

In November 2022, the Wetlands habitat reopened to the public. Conor McGarvey, who spearheaded the project, describes the experience of seeing the completed project for the first time:

“One of my favourite moments was when the scaffolding was removed, and I could walk into the habitat and see it all, how much brighter it was.” He continues, “Living in Western PA, we don’t get the most sunlight, but the sunlight that came through the clouds really popped. It was a very noticeable change. The etching on the glass is a very pretty one as well, and that was well-received by our staff and visitors. People genuinely loved it.”

The Wetlands habitat is a legacy conservatory that deserves to be seen and loved. It’s been through its share of wear and tear over the last fifty-odd years, but today it stands once again as a luminous environment full of natural light. A fully renovated Starphire® curtain wall using acid-etched glass improves daylighting in the space, while an AviProtek® bird-friendly pattern on the exterior walls supports the National Aviary’s commitment to bird conservation.

These days the Wetlands habitat has a new lease on life, thanks to dedication, ingenuity and expertise from the staff at the National Aviary and Montgomery-Smith, Inc.

If you like what you see in this structure, you’ll love the variety of options available with Walker Textures® and AviProtek® glass. It all starts with samples. Why not refresh your sample library today?

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Acid-Etched Glass Improves Daylighting at the National Aviary Wetlands Habitat

About the National Aviary

The National Aviary is America’s only independent indoor nonprofit zoo dedicated to birds. Located in Allegheny Commons Park on Pittsburgh’s historic Northside, the National Aviary is home to more than 500 birds representing more than 150 species from around the world, many of them threatened or endangered in the wild.

The National Aviary’s large walk-through habitats create an experience unlike any other—an intimate, up-close interaction between visitors and free-flying birds, including opportunities to hand-feed and meet many species rarely found in zoos anywhere else in the world.

The Wetlands presented by Peoples is an expansive, indoor habitat where more than 30 different bird species fly freely. The largest habitat at the National Aviary, the Wetlands underwent a total renovation, reopening in 2022. Today, this space includes hundreds of plants and trees with ample natural light filtering through more than 1,200 panels of bird-friendly glass. Every element of the habitat’s design was planned to encourage the natural behaviours, like nesting and preening, of the more than 100 birds that call the Wetlands home.

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About Montgomery-Smith, Inc.

For over thirty-seven years, Montgomery Smith Inc. has been providing professional services for the preservation of historic greenhouses and conservatories throughout North America, as well as design services for the construction of new greenhouse structures for research, education and public facilities. Montgomery Smith Inc. also offers expertise in the design and development of new innovative environmental control equipment and controls for the rehabilitation of period glasshouses, new greenhouses and conservatory spaces.

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