When TBDA embarked on the pursuit of sustainability, we knew that energy efficiency would be a central issue since buildings are a major source of the emissions that drive climate change. But how could we know how far to go beyond rules of thumb and code prescription to optimize our designs best?
In 2010, an answer came when Tom’s training from Phius introduced him to a sophisticated tool we’ve been using ever since: the energy model.
The common practice in architecture is to design the thermal envelope (the shape of the building and the insulation values and airtightness strategies of its walls, roofs, floors, windows, and exterior doors) using standard values derived by code and/or tradition. If an architect wants to know how it will perform, he might ask an engineer to figure that out for him after it’s designed. But we knew that wasn’t good enough.
Instead of an after-the-fact assessment, an energy model integrated with design lets us understand the energy implications of our design decisions as we go. It empowers us to know if a deeper overhang will be better for heating or cooling, if more windows will mean we need a larger heat pump, and whether a very compact or a very elongated building will use more energy.
When creating sustainable buildings, we believe we should design to rigorous standards, and we should know that our construction assemblies are appropriately robust.
During the design process, the energy model allows us to do so by means such as:
While the process involves running an advanced tool, the concept is easy. Here’s a step-by-step guide on how energy modeling works:
It all starts by creating a 3D digital model of the building. Think of this as a virtual version of the structure’s outer shell, also known as the thermal envelope. It even considers shading effects from overhangs, nearby trees, and neighboring buildings that could directly affect sunlight exposure.
With the digital model built, we assign properties to the surfaces: walls, roofs, and floors get R-values, which measure insulation, while windows, in addition to glass, frame, and spacer heat loss values, additionally get solar heat gain coefficients (how much heat enters with sunlight). This level of detail allows us to accurately predict how the building will react to varying weather conditions.
Next, the heating, cooling, and ventilation systems come into play. A proper energy model will account for what fuel systems are used, overall heating and cooling efficiencies, water heating systems, and the efficiency of the ventilation system, a key element in Passive design. With these accurately noted, we can understand how much energy the mechanical system will use seasonally and annually.
For residential projects, we account for appliances like washers, dryers, dishwashers, and stoves using the specific appliances’ data, with historical use data to estimate how much those appliances will be used. Similarly for residential projects, lighting is generalized as a power density, and is not a major energy driver in this era of LEDs. In commercial buildings, lighting and equipment use is based on specific fixtures and occupancy schedules for more precision, since there is a wide variation in consumption from, say, a school to an office building to a museum.
Local climate data is foundational to the model. Temperature, humidity, and seasonal variations from a nearby weather station determine how the building will be tested, and are input as the computational backbone of the energy simulations.
Once all the details are entered, the software (we use WUFI-Passive, the modeling tool required for Phius projects) generates a detailed output of the building’s energy use. We analyze the reports (particularly the graphs showing seasonal energy demand) to understand how we may improve performance, like adding or reducing insulation, adjusting overhangs or HVAC systems, or changing window placements. Various iterations can be saved as “Cases” in the software for presentation and comparison.
At TBDA, the tool of choice is WUFI-Passive, a program designed for Phius-certified projects. It’s particularly useful because it allows architects to analyze nearly every aspect of a building’s energy use, from solar heat gain to thermal bridges.
What’s more, WUFI-Passive has a built-in library of materials and assemblies. This means architects can quickly assign properties to different building parts, making the process efficient and thorough.
Many architecture firms outsource energy modeling to consultants, but TBDA takes a different approach. By handling energy modeling of our designs in-house, the team ensures it’s fully integrated into the design process. This allows for faster decision-making, better collaboration, and a seamless client experience.
At TBDA, energy modeling is a cornerstone of every project. By integrating it into the design process, clients get efficiency and beauty integrated in the design of buildings that align with sustainability goals.
Whether you’re building your dream home, upgrading your current space, or working on a large-scale commercial building, incorporating energy modeling into your plan can save money, reduce environmental impact, and improve quality of life.
At TBDA, energy modeling is more than just a technical process. It’s a way to ensure that every building is designed with its occupants and the planet in mind. By integrating energy modeling into our design philosophy, TBDA is shaping the future of sustainable architecture.
Learn more about our residential design services, discover our commercial and institutional design expertise, or connect with us for consulting services to bring your ideas to life.