A System Performance Approach to Building Enclosures
When Everything Works Together, You Get a Building That Works
Those of us who work in building design every day understand that the structures we help create aren’t quite as inanimate as people may imagine. Fully formed by enclosure systems and filled with HVAC, electrical, plumbing and interior systems, they hum. When their occupants move in, they positively buzz.
Like a hive in nature, different elements of the building’s design and construction rely on each other. A masonry surface absorbs heat, changing the loads on climate control from season to season. An insulated wall regulates temperature, but regional and seasonal variations in vapor pressures drive moisture migration that an assembly must manage. In this highly interdependent system, every component has a part to play. Some are often an afterthought in design, but they shouldn’t be.
As building scientists, we’ve spent decades of our careers thinking about system performance and components that aren’t always at the top of an architect’s mind, but that can have a huge impact on the performance of the whole building. We find that when you think about the building enclosure as a system—outside-in and top-to-bottom—that is defined by performance, rather than viewing it as simply an aesthetically driven skin for a building, your finished project can perform as you intended and reduce your worries, too.
What is a System Performance Approach to Building Enclosure?
When you set out to design a building, your vision includes many things: end-use, constructability, aesthetics and performance. Just as these factors can overlap (a beautiful design must also be buildable) so, too, the elements of the building enclosure have overlapping functions that contribute to the overall performance of the building and to meeting your goals.
A system performance approach to building enclosure means simply understanding each component of the enclosure system to determine how it will perform with the others. That means, for example, testing not just a piece of insulation for thermal and moisture resistance, but also determining how its performance affects moisture migration and accumulation within a wall assembly. Then seeing how that same material works in a different assembly and in a different climatic region. And another. It means looking not just at individual product results from a lab, but considering real-world circumstances: What are architects designing and how must the enclosure components adapt to a building’s design, function and location?
A system performance approach to building enclosure brings three big benefits to architects. First, it makes detail development much more efficient. When materials have been evaluated and recommended based on a system performance approach, you can reduce product search time and feel more confident when specifying enclosure materials—you know they’ve been shown to work if not in your precise assembly, in one very similar.
Second, a system performance approach helps you produce a better building product. With a system performance approach, interdependent factors are part of the building plan from the get-go. That means fewer performance surprises for you and your client when the building is complete—so it manages moisture, heats, cools and protects just as you expected from outside-in and foundation to rooftop. Architects increasingly must design to meet standards for specially commissioned or green-certified buildings, manage the potential for moisture accumulation, meet energy expectations and comply with the building code. Amid all of that complexity, a system performance approach makes it easier to get there.
Finally, a system performance approach gives you peace of mind. There isn’t an architect or builder working today who doesn’t spend at least a few sleepless project nights mulling over liability concerns. A system approach backs up your personal commitment to crossing all the t’s and dotting all the i’s. If the components you’ve selected have been tested and demonstrated to work together, you can sleep soundly knowing your building—and your reputation—are protected.
Let’s take a look at how a system performance approach to building enclosures works against the two of the most important considerations in building design: moisture and fire.
The System Performance Approach to Moisture Protection
Here, we begin by quoting one of Bert’s architecture professors: “Water is the most pervasive and sinister of adversaries for an architect.” Water comes at you as a liquid, or a solid or a vapor—sometimes all three at the same time. And, it’s the number one cause of construction litigation. Plus, of course, it behaves differently everywhere. Moisture management system concepts for a building in Miami are a different proposition than for one in Duluth. Concepts are different for a design with a masonry cavity than for one with a glass curtain wall. Not to mention how the building will be used and occupied. The variables are many.
A system performance approach understands that, and looks at the variables of your building, in your location and under your use conditions. It factors in how moisture migrates as a vapor and/or leaks as a liquid and whether it might condense and contribute to mold growth or structural deterioration over time. A choice of one insulation or a particular air/water barrier may mean walls need to be more or less permeable. Regional climatic conditions may dictate a different moisture management strategy, resulting in different types of materials and so on.
So, when you are specifying enclosure components, you want to make sure that material manufacturers understand the complete moisture picture, not just the performance for the part they happen to sell and install. Ask whether what’s been recommended has been used in this same type of system before. Has it been analyzed for use in a comparable climate? With the same kind of air/water/vapor management materials? In a similar building type? Proven systems mean less guesswork, and reduced liability.
The System Performance Approach to Perimeter Fire Containment
Last summer, builders around the world were stunned—and chastened—by the Grenfell Tower fire in London. In all, 71 people died as the 27-story building was quickly engulfed in flames. Investigations revealed the building’s cladding material had contributed to the rapid spread of flames. The Grenfell fire was a reminder that construction materials and systems are complex. With stringent codes, better materials and safety elements such as detective devices, sprinklers and passive fire containment systems, modern buildings are safe. But Grenfell Tower underscored that construction material interdependencies must be understood if they are to produce acceptable system performance.
Indeed, since the Grenfell fire, we’ve seen increased attention to the properties of various materials from our own customers—architects and builders are asking more probing and informed questions about fire resistance. Just as with moisture management, measures of fire performance vary by application and can be affected by a wide range of variables. For example, in the case of floor slab fire resistance-rated perimeter fire barrier details, a tested and proven (per ASTM E 2307-Standard Test Methodology for Determining Fire Resistance of Perimeter Fire Barrier Systems using the Intermediate-Scale, Multi-story Test Apparatus), non-combustible insulation can contain the interior spread of fire, and in some cases, systems provide fire spread protection from exterior fire propagation. But, as an assembly, it also has to be paired with the proper smoke/air sealant to keep deadly smoke from spreading, as smoke inhalation is the leading cause of fire-related deaths.
Perimeter fire barrier (PFB) assembly testing dates back more than 20 years and Owens Corning played a pioneering role in developing the first PFB-rated systems. But even with extensive testing resources, tested assemblies rarely match real-world designs with 100 percent precision—there are simply too many variations in design. Instead, the industry must rely on large sets of data that can be matched up to real designs as much as possible. In our system performance approach, for example, we serve as firestopping consultants with clients. Even if the lab hasn’t fire tested an exact assembly, we’ve most likely tested similar components and systems and our engineers can reliably predict performance. This kind of attention to detail and bank of knowledge are critical in developing “engineering judgments” that architects and code officials can rely on.
Some new designations can help in understanding the ratings of materials and systems, too. For example, the Department of Homeland Security’s new SAFETY Act Designation recognizes products that qualify for protecting builders from liability in the event of an act of terrorism on their building. This can be an important designation for architects and specifiers to consider not only in high-profile buildings, but also hotels and other potential target locations.
Installation is Part of the System, Too
In the system performance approach, installation is where the rubber meets the road (or the insulation meets the cavity!) Even the best-tested and rated assemblies can fail to perform to expectation if installation goes awry, so the system performance approach should through installation as well. Work with your enclosure partner to consult on installation and find out if they are open to providing inspections or quality audits on-site. Choose an enclosure partner who can provide detailed component drawings that outline the proper installation criteria for PFB systems. Make sure the crew has access to any installation instructions or training available from the manufacturer as well. Take advantage of special installation considerations that can maximize performance.
An Enclosure Approach That’s Built to Last
In our Insta-everything world, architecture is an ever-more unique profession: It’s work that sticks around. The building you design today might go from the height of style, to vintage-cool. Occupants will come and go. It will bask in sunny days and weather harsh storms. With the right approach and enclosure components, your building will stand up to all of it and more. A system approach to building enclosure helps you design a building that stands for performance and peace of mind—from the ribbon-cutting ceremony to decades into the future.