As the effects of climate change intensify across the world, the AEC industry is shifting toward green building to effectively address the climate crisis. In 2020, members of The American Institute of Architects (AIA) overwhelmingly approved a resolution making environmental stewardship the organization’s top priority. Since then, steady progress has been achieved to develop a Climate Action Plan, evolve the Framework for Design Excellence, and increase participation in the 2030 Commitment. The building and construction sector is responsible for 36% of energy consumption, 38% of energy related carbon emissions, and 50% of resource consumption globally. These percentages are expected to double in total footprint by 2060, exacerbating the negative effects of climate change on the environment. The Intergovernmental Panel on Climate Change (IPCC) 2021 Report warns of increasingly extreme heatwaves, droughts and flooding, and a key temperature limit being broken in just over a decade. The world must act fast to avoid these catastrophic events, and decarbonizing the built environment is a major step in the right direction.
Many government organizations and climate-conscious entities are pushing for all new buildings, developments, and renovations to achieve carbon-neutrality by 2040. Architects, engineers, and all parties involved in the building design process must begin implementing sustainable strategies into their workflows to achieve these goals and make a significant impact in the fight against climate change. In this e-book, we outline the differences between net-zero energy and net-zero carbon and provide key design strategies to help architects and engineers meet performance targets.
What is Net-Zero Energy (NZE)?
Net-Zero Energy refers to the ability of a building to offset the amount of energy required to build and operate throughout its lifetime. A building can be designed toward net-zero and offset its energy use in three ways:
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Producing energy onsite via equipment like solar panels or wind turbines.
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Accounting for its energy use through clean energy production offsite.
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Reducing the amount of energy required through design optimization.
These are typically complementary strategies, with the first option directly linked to the initial costs of the building design. Achieving NZE is not technically dependent on the building being efficient, but the most effective and cost-efficient strategy to achieve NZE is reducing the energy load and then utilizing renewable energy to offset the remaining energy use requirements. Optimizing the energy requirements of a properly designed building exponentially helps reduce power demand and the amount of power to produce or offset.
What is Net-Zero Carbon
Achieving NZC requires the reduction and offsetting of non-sustainable building materials and construction practices that cause high carbon emissions, like specifying building materials with low kgCO2e values. Similar to achieving NZE, the reduction of carbon has an exponential effect on a building design that is net-zero carbon.
Net-Zero Carbon = Total Carbon Emitted - Total Carbon Avoided
Design Strategies
Reduction is the overarching design approach for all net-zero strategies as it directly affects the energy/carbon required to offset later. Reducing the energy demand on a building provides the appropriately sized system for building operations and can lead to large cost savings. Reducing embodied carbon through material decisions often results in enhanced occupant experience by decreasing harmful off-gassing from chemicals that affect the occupants' productivity.
It’s important to note that rule-of-thumb concepts are not enough to make a net-zero building, as each building and its conditions are unique and optimization is the key to striking the neutral-balance. However, there are common design strategies that help teams understand the impact of their decisions. Applying any number of the below strategies during your design process will guide your work toward energy and embodied carbon reduction and keep your project on track toward net-zero.
1. Passive Strategies
Designing with passive strategies is about understanding the environmental constraints of the site and designing a response that does not require active mechanical systems. Examples include using ambient energy sources to cool, heat, shade, or ventilate a building space. Working with the existing natural conditions without requiring added electrical load helps decrease the energy required to offset for a net-zero building. Environmental qualities have a critical role in design to know what is specifically needed to minimize heat transfer through the building envelope (exterior walls), which will then rely less on mechanical systems to maintain occupant comfort levels. The challenge with designing for passive strategies is that they must be incorporated in the early stages of the process to be effective.
2. Solar Shading
Solar shading is a form of solar control that can be used to optimize the amount of solar heat gain and visible light that is admitted into a building. Solar Shading is a powerful passive strategy that if fully utilized can have a massive impact on a building’s overall performance and space quality. A good way to think about this is to consider that the heat added to the inside of your building has to be adjusted to stay at set temperature levels, typically by an HVAC system. The less the mechanical system has to work, the less energy you need to use, and the more likely your design will reach net-zero. Solar shading encompasses a large scope of design strategies, like WWR (Window to Wall Ratio), Glazing Placement, Fenestration Performance, Shading Elements, among others.
Using this strategy, designers can reduce energy use and have a strong impact on the thermal and visual comfort of the occupants by preventing overheating and glare during sunny seasons in the year. However, the effectiveness of the shading strategy is dependent on multiple factors, including shading device type, depth, context, and building program.
3. Active Strategies
A building's energy use refers to the energy required to operate and sustain the project once it's occupied. The metric is expressed as the energy per square foot per year (kBtu/ft2/yr), or as it is more commonly known, as the EUI or energy use intensity. By calculating the energy a building consumes annually, designers can better predict the project’s cost as it is directly linked to a building's energy consumption.
EUI breakdown includes heating, cooling, lighting, equipment, fans, pumps, and hot water, representing the mechanical system of a functional building. A more detailed overview of what is covered in these categories can be found here.
The goal is to increase the efficiency of the active system to decrease the demand for energy overall. Showing a reduction of energy use is helpful, but to reach net-zero energy the optimal overall solution is crucial as every project has many variables and entities involved that don't all have net-zero as the top priority. Optimizing for energy reduction and initial cost helps the whole team quickly reach an informed decision on the best route forward with the best performing options at the table. Optimization is the core powerhouse of reaching net-zero building design.
4. Renewable Energy
On-site renewable energy is another essential tool for reaching net-zero. Off-site renewable energy is also essential but requires live operational data from the source energy (power plant) and is thus outside the scope of building design. Providing energy generation is the final tool for net-zero energy design and is possible through technologies that produce electricity, like wind or photovoltaic "solar" panels. The strategy is simple: Use natural energy sources like the wind or the sun to generate electricity.
For a building to reach net-zero, this strategy must produce enough electricity to cover what it uses annually. For example, solar panels are an assembly of silicon cells mounted in a frame with wiring that helps absorb and convert sunlight into usable electricity. By calculating the total square feet of panels and the type of panels used, designers can calculate the annual power generation of the building project. Power generation is the final piece of building design to reach both net-zero-energy and net-zero-carbon status.
To achieve positive results, it is necessary for the designers and all the actors present in the construction to have access to information and data so that they can choose the best solutions and strategies for each situation. In this sense, analysis and simulations are valuable resources. Cove.tool’s drawing.tool is a free modeling platform that supports the designer during design, analysis and prototyping. In addition, the company is launching the International Architecture Design Competition: Carbon Positive Affordable Housing to discover design ideas that can be replicated in multiple neighborhoods, while fighting climate change and mitigating the housing crisis.
Learn more about the tool in our catalog.
