Within the building and construction industry, embodied carbon refers to the carbon dioxide emissions produced from building materials and construction methods throughout the manufacturing and construction process, including building maintenance and future demolition. Additionally, buildings generate carbon dioxide emissions through their operations. Operational carbon includes carbon generated from heating, cooling, lighting, ventilation and other mechanical systems integral to the daily use of the building. The Global Alliance for Buildings and Construction highlighted in their 2018 Global Status Report the significant impact of the building and construction industry on global CO2 emissions, at 39 percent. Of that number, less than one-third is generated from building construction and materials. The remaining portion (28 percent of total global CO2 emissions) is attributed to CO2 emissions resulting from building operations. While strategies selected for building materials and construction methods have substantial benefits for the environment, as an ongoing generator of carbon, decreasing the carbon emissions from building operations can likewise provide a lasting opportunity to reduce environmental impact.
Using Autodesk Insight to model and compare The Branches R+D concept design with a typical building in the same location, assuming typical annual energy billing, design decisions consider model-driven data regarding the following factors: window-wall ratio (glazing area to gross wall area impacts daylighting, heating and cooling), window shading (impacts HVAC energy use), photovoltaic (PV) surface coverage (assuming areas for maintenance access, rooftop equipment, and system infrastructure), and wall construction (ability to resist heat losses and gains).
The orientation and massing of the building must consider a number of variables simultaneously for maximum overall performance. Balancing the desire for sunlight to reach the podium courtyard with the need for a large surface area on the south-facing façade, the building was oriented with the courtyard facing north. By widening the open edge of the courtyard and stepping the building massing
down toward the south, sunlight still reaches the courtyard. At the same time, a large surface area is dedicated to photovoltaic panels.
While most of KTGY’s R+D concepts exist on theoretical yet typical site locations, The Branches concept addresses a specific site in Washington, D.C. By selecting a specific site, the location-specific parameters, such as climate considerations, solar orientation, prevailing winds, and typical energy usage, guide critical design decisions leading to a high-performance solution. Using site-specific data, design choices more effectively reduce energy consumption while addressing other localized sustainability concerns, including access to natural resources. However, the design strategies utilized for The Branches are also intended to easily adapt to other sites in alternative locations.
The Branches incorporates an array of strategies for high-performance multifamily design with the intent of reducing environmental impact throughout a building’s functionality. Beginning by minimizing the need for heating and cooling systems through deliberate solar orientation, directional shading devices, and natural ventilation, The Branches concept design then proposes a variety of systems for on-site energy generation. Features, including water collection, recycling, waste management and composting, further support the high-performance design goals of this concept design.
In addition to a series of high-performance design elements, environmental education components and resident wellness features integrate throughout The Branches’ building design for a holistic approach to sustainable building design. Subtle design choices, such as wider feature stairs, biophilic interior design, and prioritized alternative transportation, encourage lifestyle choices that promote individual health and wellness. Distinctly exhibited sustainability features, including a clear explanation of their relevance, urge residents and visitors to participate and support the successful implementation of the many green building strategies.
A metal scupper panel façade collects rainwater to be treated for on-site reuse and irrigation. A river of harvested rainwater runs beneath the floor of the residential lobby, exhibiting the rainwater collection process to residents and visitors. Integrated educational features highlight sustainability, health and wellness.
Windows placed on opposing walls allow natural ventilation through the units, providing fresh air and reducing the cooling load. From the energy use prediction given by the Insight model for The Branches of 30 cents per square foot per year, each unit’s energy expenditure is estimated to be approximately 125 to 308 dollars per year, as compared with 320 to 790 dollars for typical units of the same square footage.