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Designing for Net Zero Energy

Trimble technology helps maximize efficiency in designing Net-Zero Energy building

The interest in constructing Net Zero Energy (NZE) buildings has been steadily rising in the developer market and the building and design community is responding to the challenge. In fact, in many cases they are helping to spearhead progressive projects that are marvels of ingenuity, engineering and forward-thinking design.

Zero-energy buildings are optimized to produce as much energy as they use over the course of a year. They include a wide variety of energy efficiency measures such as high-efficiency heating and cooling equipment, appliances, windows and doors, and more advanced renewable energy solutions such as solar photovoltaics and geothermal energy systems.

Developing a NZE building or home begins with smart design.

The eCasa Project in Washington, DC, aims to deliver affordable, high-performance housing with a specific performance goal of achieving NZE status. The six-unit two-story buildings were designed by Inscape Publico, a nonprofit architecture firm, for Mi Casa, Inc., a non-profit organization that serves low-income families and focuses on sustaining diverse and healthy communities. 

When it comes to designing NZE buildings, each option for walls, roofing, windows, lighting, etc., impacts energy usage. The type of materials selected also contribute to the initial cost to build and the cost over time to heat, cool and maintain a home. Trimble’s Sefaira software takes the guesswork out of evaluating various design choices by identifying the options with optimal impact, helping the design team to refine not only the project design but also the project goals.

Faced with challenges to the project—limited budget, limited palette of building materials, tight project timeline—Inscape Publico proceeded to design the building blocks for the eCasa Project and demonstrate that the project was on track for NZE status.

To achieve their NZE goals, the design team had to minimize energy consumption by utilizing high-performance building construction methods and specifying high-efficiency appliances and systems. They had to specifically include highly efficient water fixtures; they also needed to calculate how much renewable energy would be generated using pre-specified solar photovoltaic panels. The baseline building performance using the selected materials determined how much renewable energy needed to be generated to achieve net zero. 

To get started, the design team set up the analysis model in Sefaira, inputting the pre-determined envelope, HVAC values and baseline variables such as occupancy, lighting power density, plug load, temperature set points and diversity factors. Potential strategies were investigated related to shading and water fixtures, with a goal of high efficiency and reduced energy use.

Having optimized the building envelope for performance, the next step was to offset the energy consumed by generating as much, or more, energy on site. At this point, the team input predetermined solar photovoltaic specifications to calculate the expected output and confirm that NZE consumption could be achieved with two arrays of 18 photovoltaic panels per block.

Sefaira enabled the team of Inscape Publico and Mi Casa to calculate the annual energy consumption, investigate energy-saving strategies, and estimate renewable energy generation, helping the project reach NZE status. Future collaboration between Mi Casa and the DC Department of Housing and Community Development will make the eCasa Project scalable to multiple sites, while addressing the need for energy efficiency to meet cost and conservation goals.