What Is A Net Zero Energy Building Strategy?

What is a Net Zero Energy Building?

A net zero energy building is a highly energy efficient building that produces as much renewable energy on-site as it consumes over the course of a year (1). The goal is for the building’s net energy consumption from fossil fuels to be zero or very close to zero. This is typically achieved through a combination of energy efficiency measures, on-site renewable energy systems like solar photovoltaics, and grid interaction strategies (2).

There are a few ways that a building can achieve net zero energy status. It can greatly reduce energy use through efficiency and passive design, then meet remaining needs with on-site renewable energy. Or, it can produce more renewable energy than needed and export the surplus to the grid. Some net zero buildings are connected to the electricity grid, while others are disconnected or “off-grid” (3). The balance of production and consumption is calculated over the period of a year.

Benefits of Net Zero Buildings

Achieving net zero energy use provides several key benefits:

Environmental Benefits

Net zero buildings produce as much renewable energy as they consume from the grid. This allows them to greatly reduce greenhouse gas emissions associated with their operations. By minimizing reliance on fossil fuels, net zero buildings help protect the environment and combat climate change.

Financial Benefits

The energy efficiency and renewable energy measures implemented in net zero buildings substantially reduce energy costs. Net zero buildings often see 50-70% reductions in utility bills compared to conventional buildings. The savings from lower energy use can help offset the marginal additional costs of energy efficient design and renewable energy systems.

Marketing and Public Relations Benefits

Constructing a net zero energy building highlights a strong commitment to sustainability. It provides great marketing exposure and helps attract tenants or customers seeking to associate themselves with green buildings. Net zero buildings can also help companies attract and retain employees who value sustainability.

Key Strategies to Achieve Net Zero

Net zero buildings work to minimize energy use through efficiency before generating energy on-site through renewables. The strategies typically focus on three main areas:

Energy Efficiency

Energy efficiency improvements, including high performance insulation, windows, HVAC systems, and appliances significantly reduce the energy needs of a building. Strategies like air sealing, high R-value insulation, ENERGY STAR certified windows and equipment, and high-efficiency HVAC systems like heat pumps can reduce energy use by 30-50% or more (Source).

Renewable Energy

On-site renewable energy systems like solar PV, wind, and geothermal provide emissions-free energy to offset the reduced loads of an efficient building. Solar PV is most common, but all locally available renewable resources should be utilized. Renewables can often supply 70-100% of a net zero building’s energy needs (Source).

Water Efficiency

Water efficient fixtures like low-flow toilets, faucets, and showerheads, as well as rainwater harvesting for landscape irrigation or other non-potable uses, reduce the water requirements of a net zero building.

Passive Building Design

Passive building design focuses on optimizing a building’s efficiency through architectural elements and material choices. This helps reduce energy consumption while maintaining comfort. Key strategies include:

Building Orientation – Properly orienting a building to maximize southern exposure in the Northern Hemisphere (or northern exposure in the Southern Hemisphere) takes advantage of passive solar heating and natural lighting. Windows are strategically placed to optimize solar gain in the winter and minimize overheating in the summer.

Natural Ventilation – Operable windows and careful building design allows passive air flow through the building for natural ventilation needs. This reduces the demand for mechanical ventilation.

Thermal Mass – Materials with high thermal mass, such as concrete, bricks, and tiles, stabilize indoor temperatures by absorbing heat during the day and releasing it at night. This passive thermal regulation reduces heating and cooling loads.

Shading – External shades, overhangs, trees, and other shading devices help block direct sun exposure during the hottest times of day. This prevents overheating and reduces the need for cooling systems.

Active Technologies

Active building technologies refer to systems that require electricity or other external energy to operate. These technologies help reduce energy usage and enable onsite renewable energy production. Some key active technologies used in net zero buildings include:

High Efficiency HVAC – Heating, ventilation and air conditioning (HVAC) accounts for a large share of energy usage in buildings. High efficiency HVAC equipment like variable refrigerant flow (VRF) heat pumps, Energy Recovery Ventilators (ERVs), and demand-controlled ventilation can significantly reduce HVAC energy usage compared to standard systems.

Smart Lighting Controls – Advanced lighting controls like occupancy sensors, daylight harvesting sensors, and dimming systems optimize electric lighting usage. Studies show smart lighting controls can reduce lighting energy usage by 50-70%.

Energy Recovery Ventilators – ERVs recover heating and cooling energy from exhausted indoor air and transfer it to the incoming outdoor fresh air stream. This significantly reduces HVAC system loads for heating and cooling ventilation air.

On-Site Renewable Energy

One of the defining features of a net zero energy building is the use of on-site renewable energy systems to help offset the building’s energy consumption. There are several common renewable energy technologies used for this purpose:

Solar photovoltaic (PV) panels generate electricity from sunlight that can power lighting, appliances, and other electric systems in a building. Solar PV panels can be mounted on rooftops, building facades, or ground-mounted arrays. According to the U.S. Department of Energy, solar PV accounted for over 40% of on-site renewable energy generation in net zero energy buildings as of 2020.^[1]

Solar thermal systems use solar energy to heat water, which can then provide domestic hot water, hydronic space heating, or serve industrial processes. Popular solar thermal collectors include flat plate, evacuated tube, and concentrating technologies.^[2]

Small wind turbines can also generate electricity on-site when mounted on or near buildings. Optimal conditions are sites with consistent wind speeds above 9 mph.^[3]

Geothermal heat pumps use the constant temperatures found just below the earth’s surface to provide heating and cooling for buildings. This is done by circulating fluid through underground pipes or down wells to transfer heat between the building and ground.^[4]

Using a combination of these on-site renewable energy systems can help create a robust net zero energy strategy tailored to the building’s location and needs.

Grid Interaction

Network metering and bidirectional energy flow are key aspects of net zero energy buildings. To enable grid interaction, net zero buildings utilize technologies like smart inverters, batteries, and building energy management systems.

Net metering programs allow buildings to export excess renewable energy to the grid and receive credit for it. This helps balance on-site generation and building loads over time. Grid-Interactive Efficient Buildings can optimize the timing of on-site generation and load to maximize self-consumption and grid exports when most valuable.

Feed-in tariffs provide financial incentives for renewable energy fed into the grid, helping offset net zero costs. Load shifting involves strategies like pre-cooling spaces to reduce peaks when energy costs are high. Overall, intelligent grid interaction is key for net zero buildings to contribute to grid stability as renewable penetration increases.

Embodied Carbon

Embodied carbon refers to the greenhouse gas emissions associated with materials and construction processes throughout the whole lifecycle of a building. This includes emissions from extracting, transporting, manufacturing, installing, maintaining, and disposing of construction materials.¹

To minimize embodied carbon, net zero energy building strategies promote using low carbon and responsibly sourced construction materials such as:²

• Locally sourced materials
• Renewable and recycled materials
• Materials with environmental product declarations

Calculating embodied carbon allows architects and builders to make informed material choices. Tools like life cycle assessment software can estimate emissions across a building’s lifespan. Targets can then be set to reduce embodied carbon through material optimization.

Commissioning

Commissioning is a crucial process for achieving net zero energy in buildings. It involves rigorously testing all building systems to ensure they are installed, calibrated, and performing according to the project requirements and design intent. Thorough commissioning helps identify and resolve any deficiencies before occupancy so that buildings operate as efficiently as designed

Commissioning for net zero projects focuses on testing the performance of the building envelope, HVAC, lighting controls, renewable energy systems, and other energy-related components. Special attention is given to air tightness, insulation, glazing, shading, HVAC controls, and metering. The commissioning agent develops detailed test procedures, oversees performance tests, reviews results, identifies issues, and verifies resolution of any problems.

Another key aspect of commissioning is training building operators and occupants on energy-efficient building operations and maintenance best practices. Proper training helps ensure energy performance persist over the lifespan of the building. The commissioning process also establishes ongoing monitoring and analysis of energy use data to track and optimize building performance.

According to the Building Commissioning Association, robust commissioning is invaluable for achieving net zero targets while meeting comfort and indoor environmental quality requirements. As net zero buildings become more complex, commissioning will continue to play an integral role in their successful delivery and operation.

Net Zero Certifications

There are several green building certifications that projects can pursue to validate their net zero energy performance and strategies, some of the most well-known are:

• LEED Zero – Projects must achieve LEED Platinum certification and TRUE Zero Waste certification at the Platinum level from GBCI. LEED Zero represents a new level of achievement in green building.
• ILFI Zero Energy Certification – Allows projects to demonstrate net zero energy performance. Focuses on net zero energy building over 12 months of continuous occupancy.
• Passive House – Validates energy efficiency and performance. While not specifically a net zero program, achieving Passive House is a key strategy.
• Living Building Challenge (LBC) – Projects must meet requirements including Net Zero Energy. LBC is considered the most rigorous green building program.

These leading programs allow projects to benchmark and validate their net zero energy goals. Certification provides third-party validation of strategies and verifies net zero performance over a occupancy period. Pursuing established green building programs, at the highest certification levels, is key for projects targeting net zero energy.