The Ever-Evolving Building Envelope
Richard L. Peck: You've commented in the past on the growing complexity of building exteriors. Would you discourse upon that?
Richard Robison, AIA, CCS: This is indeed a time of increasing complexity. At the high end are new materials like ethylene-tetra-fluoro-ethylene film, or ETFE, and other fun new materials also that are used to enhance a building's appearance and allow for great plasticity of building form. Titanium is a new material that has had a lot of press in recent years. These exotic materials are not the mainstream, but they work their way in over time.
For instance, photovoltaic panels have been used for years to power space satellites, and have now come down to earth to alight on, and light up, our buildings. We are now using them on our research laboratories and other buildings designed to showcase energy efficiency. Not long ago they were relegated to flat panels perched on the roof. A recent development is their incorporation in the building skin. Photovoltaics are now worked into glass exteriors not only to generate clean power from sunlight, but to achieve various design effects-shadings, ceramic frit-like patterns, and the like. Several glass manufacturers are offering these, as well as metal cladding manufacturers. And the roofing people are laminating thin film photovoltaics to single-ply membranes.
Our firm has never done a great deal of work with the all-glass box exterior with mirrored or colored glass, but going back some 15 years, and increasingly since then, we have incorporated sunscreens in very exciting ways. Variations of sunscreen are an exterior product of choice for us. They are an accessible technology that is reasonably economical, something we can model, design, and detail ourselves without relying on exotic technology or experimentation. Whereas our earlier designs were based on time-honored rules of thumb, we now model the concept design in the computer to verify throughout the day and year that the sun and the sunscreen will interact as intentioned. More and more manufacturers these days are offering sunscreens that are a kit of parts and easily customizable.
Peck: Which plays off a comment you once made about the “kit of parts” approach to other components of the building envelope, such as windows-the sheer number of components involved these days to choose from and coordinate.
Robison: Windows are a challenge because they combine so many parts and components at the interface-glass, metal, fasteners, joint sealant, gaskets, anchors, sometimes operating hardware, each of which has to interface with the building skin, mortar, sealants, tapes, moisture barriers and so forth. Will material A stick with B, or will it need an intervening C? Will a manufacturer's given material A, which is similar but not identical to another manufacturer's material A, be more or less suitable for A plus B? There is very little that is truly generic in today's marketplace. If you take three materials that interface with each other, and each is offered by three manufacturers, and all are quite similar but not identical, you can see that the permutations of 3 x 3 x 3 are already 27. A single window or other opening can have many more than three materials that intersect. Complexity is a constant challenge.
Peck: On top of which, add the special requirements of healthcare facility envelopes in terms of infection control, air handling, and moisture resistance, correct?
Robison: That's correct. Clients want skins performing initially and in the long-term to prevent drafts, mildew, or the slightest water infiltration, 24/7. With all the pieces and parts involved these days, it's quite a challenge.
Peck: Doesn't success depend largely on how well contractors in the field implement building envelope plans?
Robison: Success is tied directly to communication and collaboration on the job site among the designer, the general contractor, the installer, and the manufacturer's technical department. The current project will not and cannot be identical to the previous project, so without clear communication and collaboration, you're simply experimenting from one project to the next when putting the envelope together.
Peck: Might this collaboration start as early as design development?
Robison: In today's marketplace it often does. With a construction manager providing preconstruction services, you'll often see an installer at the table early on or, failing that, the manufacturer's technical representative or even outside consultants, all trying to work through in detail how skin construction will be conducted on the job site.
Peck: Is off-site fabrication of building skin components becoming more a factor?
Robison: We've seen unitized curtainwall systems used over the years, although not very much in our area of the country, the Southeast. Here our climate allows stick-built systems to be constructed on almost a year-round basis, and our labor costs aren't as much a factor as in other areas of the country. A unitized system is favored in areas where labor costs and weather are factors, because it allows for shop fabrication of whole units and significant compression of the field construction schedule.
Peck: What is your view of some of the new building envelope technologies coming down the pipe, such as double-skins allowing for air handling via convection, among other things?
Robison: These double-skin exteriors are very interesting but beyond the reach of the garden-variety construction budget right now. They are one of several interesting technologies coming along. Several years ago I gave an in-house “lunch ‘n’ learn” in which I suggested that building skins would evolve into structures that respond actively to the environment. Double skins are part of that evolution. Building envelopes today are typically static; they don't move, they don't change. Responding to demands for light versus darkness, privacy versus views, keeping heat in or out of a building-this is a lot to ask of a static surface. In past years, of course, we did have responsive exteriors-windows opened or closed, awnings were extended or retracted, depending on the circumstances of the moment. I think modern iterations of this will see skins responding with insulation values that rise and fall or that change in other ways. We are already seeing the first attempts in the marketplace, such as moisture barriers that allow moisture vapor to pass and glass that changes from clear to opaque. I believe we will see amazing new products that respond to the environment in very innovative ways.
Peck: Do you think buildings, including healthcare facilities, will become more flexible in their access to and use of fresh air?
Robison: In America we've become accustomed to heated, air-conditioned buildings. No one is willing to put up with drafts, winds, dust, heat, or cold these days. You don't see the paperweights of past years that kept papers on our desks when wind blew in through the window anymore. Fresh air itself is a challenge, of course, in moist or hot climates or where allergens are a problem.
We might see a return to “right-sized” fresh air and creative approaches to doing this someday-we're just not there yet. One new technology I see coming is what I call “dumb building” technology. Right now we can computer model the building's exterior to set a base line for peak energy efficiency in terms of glazing, sunscreens, insulation, air handling and filtration, and the like. This represents the balance point where the minimum energy input is achieved. In the future, “smart” technology will allow the building's exterior to adjust to specific conditions during the day and over the seasons. That's a future development I believe we can anticipate with some confidence. HD
Interview with Richard Robison, AIA, CCS, Principal, Lord, Aeck & Sargent Architecture, Atlanta by Richard L. Peck, Editor
Healthcare design is changing the look and function of hospitals throughout, from lobby to loading dock-but nowhere is the change more obvious than in the exterior appearance of the buildings, the look of the building envelope. From the concrete and/or brick monoliths of yesteryear, hospital exteriors have evolved into the warmer, more inviting, more colorful and more frankly beautiful designs of today. Along the way the challenges of putting the building envelopes together and making them work for healthcare have multiplied exponentially. Envelope design has become, indeed, an architectural specialty unto itself. Recently one such specialist, Richard Robison, AIA, CCS, Principal of Lord, Aeck & Sargent Architecture based in Atlanta, Georgia, discussed this evolution with HEALTHCARE DESIGN Editor Richard L. Peck.