Designing Green: The Seen and the Unseen

Integrating components to achieve holistic performance

By Peter J. Arsenault, FAIA, NCARB, LEED AP

The movement for green and sustainable building design continues to grow and pick up steam for multiple reasons that operate totally outside the realm of politics. Building owners recognize real financial and personnel advantages with green buildings and are coming to expect that their design and construction teams have the knowledge and expertise to create energy-efficient, environmentally sensitive, and healthy buildings as part of their normal design process. Accordingly, architects and other design professionals have become better educated on how to produce and advocate for such designs, sometimes taking advantage of advanced computer software tools to help in the process. Similarly, construction professionals have developed standard practices or teamed with specialists to be sure they can provide green building work competitively. Concurrently, product manufacturers have invested heavily in finding ways to both operate in a sustainable manner and to create products that pass muster as green and sustainable too.

Pushing this movement along is the existence not only of energy codes and even the International Green Construction Code (IgCC), but also a number of voluntary standards and rating systems to help identify just how green or sustainable a building really is. The U.S. Green Building Councils’ LEED program is probably the best-known one, but there are others being used too. The WELL standard is recognized by LEED but focuses on the health and well-being of occupants in more categories and in greater detail. Passive House is raising the bar on energy efficiency not only for single-family residential buildings but also for multifamily construction—its fastest-growing area of certification. And the International Future Living Institute has developed the Living Building Challenge (LBC) which goes beyond “doing no harm” to being truly regenerative and contributing to a positive built environment in multiple respects. It includes 20 imperatives organized into seven “Petals,” all of which must be achieved in order to receive full LBC Certification. Separate certifications are also available for certain petals and for a net-zero energy building.

Regardless of the standard being followed, the challenge for design teams is not necessarily how to address any individual aspect of green or sustainable design, but rather, how to synthesize multiple needs into an integrated, holistic design. That can often take some trial and error attempts at different design combinations to determine an optimal balance of benefits without detracting from other sought-after characteristics. The development of different design iterations, commonly using computer modeling or simulations, has given rise to a 21^st century “iterative design process.” Ideally, this process allows for several different design scenarios to be developed, first at a large scale or “massing” level, to compare the differences between them on environmental, energy, or wellness terms. Once a conceptual design is settled upon, then a more detailed analysis can take place where individual components can be studied to determine how to optimize each of them in relationship to overall design and other components. Finally, specifications for materials need to be coordinated with the design to maximize the green and sustainable qualities being sought for the materials that are used in the building.

With all of the above in mind, this course will look at several aspects of green and sustainable design, specifically with the idea of integration and optimizing design iterations, components, and specifications.

Durable, Multifunctional Building Enclosures

Buildings, by definition, separate the outdoor environment from the indoors to provide shelter and comfort for people. The building enclosure (walls, roofs, floors) defines that separation and, in addition to structural and finish materials, is comprised of four fundamental building components: a water-resistive barrier, an air barrier, a thermal barrier, and a vapor retarder. Each of these barriers is intended to control or thwart the movement of air, water, moisture, or heat through the enclosure. The premise of green and sustainable design in regards to these items is to go beyond code levels of performance and pay attention to the details enough to be sure that all four of these components operate at a higher level for several reasons. First is to create a durable, long-lasting building enclosure system. This is required in building codes but is also the essence of what it means to be sustainable over the long term—making repeated repairs or replacing materials on a building is the antithesis of that. Second is the premise that a well-designed building enclosure will reduce energy requirements for heating and cooling that building. This is true for all of the barriers, not just the thermal barrier (i.e., insulation). A poor air barrier can cause drafts and air leaks that could require more heating or cooling energy than poor insulation would. Water or moisture penetration into a wall or roof assembly can damage and compromise the effectiveness of insulation, not to mention creating mold or other conditions that are not conducive to good human health. Hence, all of the barriers are critical.

There are numerous ways of course to create a sustainable, durable building enclosure. In framed wall construction, the place where most of these critical barriers come into play is along the line of the structural wall sheathing. Typically, in wood-framed construction, this is an engineered wood panel that is fastened directly to stud framing, providing shear support and a nailing surface for final cladding or other finishing. It is the exterior surface of this sheathing that also needs to be treated to provide a water-resistive barrier (WRB) and an air barrier to meet code and energy performance requirements. These barriers are critical not only along the surface of the sheathing but at all seams and penetrations as well. Separate products are commonly available that are either fastened (i.e., house wrap or sheet goods), adhered, or sprayed on in the field to achieve these characteristics with their performance subject to the skills of the applicators and the site conditions during construction.

While the combination of field-applied barriers has been traditional, there are products that have emerged to simplify construction, improve durability, and meet high-performance criteria. Such products were developed with the recognition that the ones that have the most chance of performing successfully over time are the ones that are easy to integrate into a building design and streamlined to install. As such, new structural sheathing products have entered the market in the past decade that integrate factory-applied water-resistive barriers plus rigid air barriers all into a single-panel system. These next-generation structural sheathing solutions help framing crews reduce the risk of improper installation of multiple product layers to help assure better performance over time. Further, such integrated structural sheathing systems rely on sealing the seams between the sheathing and around the penetrations with acrylic tape specifically designed to seal against water and air. The entire system has passed third-party testing and been shown to meet or exceed the requirements for proper water and air barriers.

Taking integration one step farther, it is also possible to specify and design with structural sheathing that incorporates a built-in layer of exterior continuous rigid insulation on the interior side of the sheathing, leaving the air and water barriers unaffected. Continuous insulation is promulgated by energy codes and green building standards, particularly Passive House, for its superior thermal performance. Walls, floors, and other building components that are only insulated between the framing members ignore the reduced thermal performance of those framing members compared to insulation. Heat can flow somewhat unrestricted through that framing and cause a thermal bridge that lowers the overall performance of the building. By providing continuous insulation over the outside of all framing, the thermal bridging is reduced or eliminated. Integrated structural sheathing that includes an air, water, and thermal barrier builds on the simplicity, effectiveness and high performance that are possible with this advanced type of product offering. A factory-installed layer of polyisocyanurate (polyiso) continuous foam insulation is available in thicknesses between ½ inch and 2 inches. When used in conjunction with stud cavity insulation, this continuous insulation provides additional R-value for reduced heat transfer in advanced wall assemblies. Combined with the high performance of the air and water barrier, the total system becomes extremely energy efficient.

Laura Gamble is a project manager for the Philadelphia-area-based architectural firm BartonPartners and has seen the need for increased energy performance first hand. “Building codes in general are driving up insulation thicknesses and tightness standards,” she says. Further, she points out, “Many of our clients are seeking out certifications that go above and beyond code such as LEED, NGBS, ENERGYSTAR certification, and others.” To meet these needs, her firm is involving building envelope specialists to review both construction documents and contractor’s installations to support the high performance expected in today’s homes and buildings. In this regard, Gamble says, “An all-in-one product that includes sheathing, a weather-resistive barrier, and flashing tape speaks to the evolution of building science. For clients who are interested, we’re specifying such systems because the building can be made weathertight quicker than with traditional sheathing and building wrap systems, which generally requires extra labor and time.”

There are also other practical implications of using this type of integrated structural sheathing product. The combined capabilities mean there are fewer products to order and install, thus changing the way design and construction teams plan materials and framing schedules. On site, the resistive nature of the sheathing means that if it is left exposed before the siding or cladding is installed, then the barriers aren’t necessarily compromised the way other materials can be, such as house wrap that is seen blowing loose. In fact, at least one manufacturer offers a 180-day exposure guarantee and a 30-year limited warranty based on the tested integrity of the system to ensure a fully weatherable exterior wall. In addition, because of its streamlined approach to achieving structure and air and water management in a single product, integrated sheathing and tape is used in many panelized and modular buildings. Here, the integrated sheathing not only compresses time schedules but helps achieve higher quality control of installation—another critical component of long-term durability.

An integrated water-resistive and air barrier sheathing also creates a unique system that improves the chances for greater long-term moisture resistance, one of the greatest threats to building envelope degradation. Typically, vapor retarders are required to be placed on the interior side of walls in colder climate zones. If any moisture does penetrate the wall and enter the construction, it may condense on the interior face of the sheathing. Products that provide moisture permeance to allow panels to dry to the outside can help alleviate this condition and contribute to the longevity of the construction.

It should be noted that such integrated systems are not limited only to exterior walls. Integrated sheathing and tape products are also used for roof construction. In fact, they have been shown to meet the FORTIFIED HOME™ national resilient building standards for a sealed roof deck. This means that they are much more likely to survive severe weather, such as hurricanes, tornados, and heavy rain, as compared to traditional sheathed roofs that do not use the tape sealing or integrated air and water barriers.

Overall, whether designing to meet the latest building codes or voluntary high-performance standards, managing air tightness, bulk water, and thermal bridging, all can be effectively addressed with this integrated approach to design and construction.

Combining Natural Ventilation and Daylighting

Virtually all of the green and sustainable building standards recognize the importance of life-giving elements in the interior environment. These elements include fresh air and daylight with specific provisions in LEED, WELL, and the Living Building Challenge (LBC) that seek positive, healthy indoor conditions. In fact, one of the required imperatives of the LBC (07) states: “Every regularly occupied space must have operable windows that provide access to fresh air and daylight.” The design challenge in providing air and daylight, however, is balancing them with the energy use implications that can accompany them. Specifically, too much daylight can also cause unwanted solar heat or glare if not controlled properly. Similarly, providing abundant fresh air into the building means that air not only needs to be moved in some manner (often involving electric fans), but it may also need to be conditioned for temperature and humidity level to maintain comfortable interior conditions. Finding creative ways to provide the right levels of daylight and ventilation while minimizing the energy required to do so is a great example of the usefulness of iterative design.

The first thing to recognize in ventilating commercial or industrial buildings is that natural ventilation is still an option. Most of us are accustomed to simply opening a window in our residences for fresh air, but too many people incorrectly assume that doing something similar in commercial or industrial buildings can’t be done. The use of HVAC systems that are assumed to run 24/7 tends to drive that perception. The reality is that natural ventilation is used very successfully in buildings of all types all around the world and has been for centuries. In some cases, there are certain times of day or times of year where outside air is very comfortable and suitable for indoor use. The incorporation of “economizer cycles” in HVAC systems is based on this, although fans are still needed for such a system to operate. Other systems use carefully placed, operable windows or louvers that allow fresh air to enter naturally in one location and exhaust out in another based on the building design. Some even use internal or external heat gains to warm the air and allow it to rise and ventilate accordingly.

A modern, sustainable version of this approach to natural ventilation is the use of top-hinged operable windows that can respond easily to different building conditions and needs. Such windows offer very effective natural ventilation and daylighting that can be controlled manually or with electric motors. In some cases, they can also be fitted with electronic controls as part of a larger energy management system in a building to allow for automatic operation based on indoor and outdoor conditions, schedule, or other criteria. Hinging at the top allows the windows to remain open even during rainy times since the water will shed off of the angled open window and away from the building.

Some manufacturers have created a fully coordinated system that can be installed as single units or in continuous runs up to 150 feet wide. When placed in long runs, they are installed in sections designed to snap together when one unit is mated with another. In at least one case, the design of that ‘snap together’ joint includes weather stripping, which creates an effective continuous louver effect. The flexibility of the weather stripping can also accommodate thermal expansion and contraction of the system. Incorporating lightweight, but thermally efficient glazing into the system allows for natural daylight in addition to the ventilation. Bill Voegele, CEO and Founder of EXTECH/Exterior Technologies, Inc., points out, “Continuous top-hinged windows have been around for years, mainly for industrial applications, and now the world is understanding that they are an architectural resource as well. They deliver massive natural light and ventilation economically and sustainably. The fact that they can be left open during normal rainfall adds to this system’s list of benefits.”

Top-hinged window/louver systems are popular with warehouses, data centers, and other new or existing facilities that need to meet high cooling demands and/or rigorous sustainability goals. They are available in systems that accept glass or lightweight, translucent polycarbonate glazing up to 1 inch thick. Typically, they are “dry glazed” with low-friction gaskets to maintain good air and water infiltration seals while allowing for thermal movement of the glazing. Polycarbonate glazing is often used because it is available with a Class A fire rating and can achieve R-values up to R-3.8. The lighter weight of the polycarbonate compared to glass means that large, continuous runs are possible up to 8 feet tall and 150 feet wide, or smaller systems can be selected to suit the particular needs of the building. Either way, the need for multiple building penetrations can be reduced. The finish on the aluminum framing can be a choice of anodized or high-performance factory-baked paints.

When using these systems in the design of a building, a computerized daylighting study can be done to place the project in a virtual environment and allow the architect to modify the design to maximize the daylighting delivered and control the solar heat gain. Similarly, the massive ventilation offered by the system relieves demand for the HVAC system. This reduces energy costs and can help with optimizing energy usage consistent with LEED or other programs. Because the system can be left open during normal rainfall, it facilitates ventilation despite inclement weather. The natural daylighting provided also reduces the cost of artificial lighting and provides the wellness benefits of natural light. When used with polycarbonate glazing, it is nearly 100 percent recyclable, further lending itself to its overall, long-term sustainability. Even when installed in a long run, each glazing panel can be repaired and replaced individually, saving on maintenance and excess waste.

Solar Screening

While allowing light and ventilation into a building is commonly achieved with window systems of some sort, there are other considerations for green and sustainable buildings too. In cases where the amount of sunlight needs to be controlled to limit solar heat gain and control energy usage, one of the most effective methods is to add an exterior treatment, such as a sun screen or awning. The exterior treatment stops the sunlight and resulting heat gain before it ever enters the window or the building, making it one of the more effective strategies for reducing heat gain in buildings. It also provides real opportunities for the creative design of building facades and exteriors.

When looking at options for sun shade materials, one common approach is to use perforated metal. This choice has the benefit of being able to select or design the amount and style of perforation to provide differing levels of light penetration and/or reflectance. In addition to keeping the building cooler in the sunlight, perforated metal can also allow controlled light and views either directly through perforations in the sunscreen or between vertical louvers or baffles. There are also any number of other creative design options for daylight and views with this material based on the needs of the building and the overall design intent.

Beyond daylight, perforated sunscreens allow air to pass through them. For building occupants, that means they can still open windows or operate ventilation systems and receive plenty of fresh air. For exterior structural design, it means that wind loading is dissipated compared to an all solid material. Both of these conditions make it easy to add perforated metal sun screens to most building types.

Of course, any material used in a green building needs to be looked at in terms of its overall attributes. Perforated metal sun screens can be specified to be made from a high recycled post- and pre-consumer content to avoid the use of virgin raw materials. On-site, the sun screens can be sized and manufactured to reduce or eliminate waste. Further, at the end of its service life, 100 percent of perforated metal can be recycled. The finishing of the metal can also be a concern, particularly if volatile organic compounds (VOCs) are involved with the finishing. Hence, it is possible to use low-VOC finishes, or for certain metals and in some building designs, no finish may be required, thus eliminating the concern altogether.

From a building use perspective, perforated metal is an economical and very durable option. It typically requires very little maintenance compared to other materials since it needs less refinishing and less cleaning over time. It is quite common for it to hold up for decades, not just years. On and within the building, perforated metal can support biophilic design, which is one of the Imperatives (number 09) of the Living Building Challenge. Under this requirement, the intent is to foster and nurture the connection between people and nature in the form of light, air, and environmental features as well as the use of natural shapes and forms. The perforated metal can be shaped and formed specifically to provide light and ventilation where it is needed but also to mimic shapes and forms from nature.

Overall, the use of perforated metal sun screens is another example of a single product or design solution that can address multiple aspects of green and sustainable design in a balanced way. As such, they can contribute to points and credits for green building certification programs, such as LEED, WELL, and LBC.

Paints and Finishes for Responsible Interiors

LEED, WELL, the LBC and other programs are specifically concerned with the impacts of the interior environment on human health. In particular, they focus on the products and materials used inside a building and their specific chemical makeup. It is easy to understand that in a closed, indoor environment, people may react poorly when regularly exposed to products that emit certain chemicals or compounds, even if the quantities are small. Hence, there has been a considerable focus to require manufacturers to declare what is in the materials or products that they create, just as food products need to list the ingredients in them for health reasons. This allows designers, specifiers, and consumers to make informed choices and compare different products for use or exclusion in buildings.

A good example of where this responsible interior concept applies is the use of paints and finishes that are formulated out of a variety of chemical compounds and elements and which can be quite ubiquitous inside buildings. Recognizing this, they are often scrutinized particularly for the amount of volatile organic compounds (VOCs) and other ingredients. In particular, under LEED v4, flat paint must meet a VOC level of 50 grams per liter (g/L) or less, while non-flat paint is allowed 100 g/L or less, as well as be emissions certified. This is a restrictive but increasingly achievable requirement as paint manufacturers work to reduce or even eliminate VOCs from their formulations.

In addition to this basic requirement, LEED v4 awards credits where an environmental product declaration (EPD) is provided as a way of communicating the results of a detailed life-cycle assessment (LCA) of the ingredients and processes involved in a product. The American Coatings Association and the U.S. coatings industry have developed a standardized format for measuring the environmental impacts of architectural paint based on a defined set of criteria. Individual manufacturers are using this format to conduct an LCA and ultimately an EPD that would allow certain brands to qualify for the appropriate LEED credits. A similar process can create a health product declaration (HPD), which discloses the chemical profile of a product, including both hazardous and nonhazardous ingredients, in more detail. LEED recognizes both the EPD and HPD as a means to demonstrate qualification for certain credits/points.

Beyond LEED, the WELL program similarly seeks to reduce VOCs and achieve transparency in product makeup. WELL Feature 04 specifically focuses on VOC reduction, while Features 11, 26, and 97 address fundamental and enhanced material safety and transparency. Some of these requirements are aligned or equivalent between the LEED and WELL standard, while others only overlap partially. Therefore, when seeking to obtain certification in either standard, it is important to review the specific language and details of what is being assessed for human health impact. Note that when reviewing the information, both the paint base and the colorants are important since adding colorant to a low-VOC paint can increase levels significantly. Some colorants alone can meet or exceed the 100 g/L threshold separate from the paint base, while other manufacturers have produced zero-VOC colorants (according to EPA Method 24): Determination of Volatile Matter Content, Water Content, Density, Volume Solids, and Weight Solids of Surface Coatings. Further, if a full life cycle (or duty cycle) of the paint or coating is being considered, then the anticipated number of repaintings will influence the total VOC emissions over time.

The Living Building Challenge takes a slightly different approach to interior health and materials used in construction. Rather than trying to identify acceptable levels of certain chemicals or compounds, they simply call for them to be eliminated completely from buildings that seek certification. Specifically, they have researched and identified a “Red List” of chemicals and compounds that are known to pose serious risks to human health and the environment. Under required imperative 10, a project must be free of anything on the Red List. The means to identify this and other imperatives comes from third-party verified information on manufactured products under the Declare program of the LBC and covered in imperative 12. This initiative focuses on product ingredients and uses an intentionally simple, color-coded summary label that declares any potential hazards. The choices for each ingredient listed can be a warning that something is 1) on the Red List; 2) another chemical of concern identified by the U.S. Environmental Protection Agency; or 3) not a hazardous chemical.

Designers and specifiers can request Declare labels directly from manufacturers and can use this information to specify materials that are free of Red List ingredients or other chemicals of concern. The International Living Future Institute, which administers the Living Building Challenge, also keeps a list of products and materials on its website that have filed declare labels (https://living-future.org/declare/). A search can be initiated by manufacturer name, by CSI Specification Division, or by geographic location in the world. Given the extensive list of products and materials, a helpful tab for “status” also provides sorted lists based on either Red List free, LBC compliant, declared, third-party verified, or LEED v4 listed.

It is worth noting that some paints and finishes can also be Cradle to Cradle Certified™. This product standard guides designers and manufacturers through a continual improvement process based on five categories: material health, material reutilization, renewable energy and carbon management, water stewardship, and social fairness. A product can receive an achievement level in each category, with the lowest representing the product’s overall mark. Product assessments are performed by a qualified independent organization trained by the Cradle to Cradle Product Innovation Institute, a nonprofit organization that manages the certification program. Every two years, manufacturers must demonstrate good faith efforts to improve their products in order to have their products recertified. Some paints meet this ongoing recertification, and evidence of the same can be requested from the manufacturers or the Cradle to Cradle Product Innovation Institute (www.c2ccertified.org/).

Architectural and HVAC Specialties

When designing a green or sustainable building, the use of rating systems and standards helps in determining the degree to which different goals are achieved. While programs like LEED and WELL recognize different certification levels, allowing designs to pick and choose which attributes to pursue, full certification in the Living Building Challenge requires that 100 percent of the building needs to comply with the criteria. The LBC does allow recognition for individual Petals that make up the total program, but everything in the requirements for the Petals must be met. The implication of this total approach is that everything in the design and/or specifications for a project needs to be looked at through the lens of a truly regenerative, healthy, and positive built environment. This can be easy to think of for the major components of a building, such as structure, facades, finishes, etc., but total compliance means that it applies to specialty products too, such as accessories, trim, grilles, and similar items used in a building.

To illustrate this concept, let’s take a look at a common and required product in most buildings in the form of metal grilles, which cover HVAC openings in walls, floors, ceilings, or exposed ductwork. Architects often like to select such products based on their contribution to the overall design intent of the building, while engineers are focused on the amount of air flow and net free area in them—both legitimate and important design considerations. Of course, there are choices in such products, and many come with the attributes of being lightweight, versatile in design characteristics, available in a variety of styles, and being manufactured from a variety of material choices. When used in a building pursuing LEED or the LBC, the additional considerations of the grilles as an installed product in a green or living building come into play, just as for any other products used. That means they need to be looked at and assessed on several fronts:

• Recycled metal content: Up to 94 percent post-consumer content recycled aluminum is possible and should be part of the specification for linear bar grilles, perforated grilles, or custom-fabricated products.
• Wood specification: For some designs, the grilles may be specified as being fabricated from wood instead of metal. In this case, the use of reclaimed wood is possible, but otherwise the wood should meet the same sustainability criteria as other wood in the building, such as Forest Stewardship Council (FSC) certification.
• Durability and ease of maintenance: The most sustainable product is one that lasts and doesn’t need to be replaced or repaired unduly over time.
• Finishes: If any finish is used on the grilles, then they need to be low- or zero-VOC content. Some powder coatings that are electrostatically applied and then cured under heat without the use of solvents may be the best choice here.

Just like other products used in a building, the use of Declare labels issued by the International Living Future Institute can be asked for and used to compare different manufactured products based on the relevant criteria above. This information can be used for LBC projects, but note too that Declare has been approved as a compliance pathway for the LEED v4 Building Product Disclosure and Optimization Credit, Option 1. Regardless of the program being pursued, all products of all sizes and types used in a building need the transparent data and information that such declarations provide.

Conclusion

Green and sustainable design requires attention to many details and many different aspects of a building. Some are obvious and visible, while some are embedded within the materials used or the nuances of the design. Either way, they all need to work together toward a whole project that is good for the people who use the building and the environment where it is located. The use of certification programs is a good way to delve into the issues and details, but ultimately, it is the design and construction team working with a building owner that can collaborate successfully to create truly sustainable, even regenerative facilities.

Peter J. Arsenault, FAIA, NCARB, LEED AP practices architecture, consults on green buildings, presents continuing education seminars, and writes prolifically on topics related to design and high-performance buildings. www.linkedin.com/in/pjaarch