How to Design a Net Zero Energy Building

The building sector emits such huge amounts of greenhouse gases that urgent action is necessary to avert climate disaster. Net zero energy buildings will play a big role in curbing global warming in the decades to come.

Most people probably think of fossil fuels in transportation when they think of global warming and greenhouse gas emissions. So it’s surprising — and important — to note that the building sector produces?nearly 40% of the world’s emissions.

To meet the goals of the Paris Agreement, the building sector must attain net zero carbon by 2050. That means billions of buildings worldwide will need to comply to keep global warming below 2 degrees Celsius.

What Is a Net Zero Energy Building?

Net zero energy buildings are buildings that make, or supply, their energy through renewable resources, which results in zero carbon emissions. Put simply, a net zero energy building is one that produces as much energy as it consumes on an annual basis.

These types of buildings can take energy from electrical grids, and send unused energy back to offset their energy consumption.

Don’t be confused by conflicting terms. NZEB stands for “net zero energy building.” ZNE is short for “zero net energy building.”

They all mean the same thing. They also might be referred to as “green buildings.”

There is a difference between “net zero” and “zero.” For example,?New York state law?says 85% of reductions must come from the state’s own industrial and energy emissions. The remaining 15% may come from carbon offsets, including in forestry and agriculture.

Carbon offsets?work whether an organization stops its own emissions or offsets its emission reductions elsewhere. The climate effects are the same.

During the 1970s,?solar panels?on the roofs of homes began harnessing the sun’s power. This reduced energy costs and helped the environment at the same time.?California?and other states created programs to encourage their use, but they haven’t gotten us where we need to be. And while solar panels are important, they can’t do the job alone.

This is because net zero energy building has to be far more holistic in its approach. It needs to include a number of factors that promote energy conservation. It also should go well beyond single-family renewable energy homes and residential buildings. It must include other building types, including commercial buildings.

Some of the ways to achieve net zero energy will be covered in the sections that follow.

How Does a Building Achieve Net Zero Energy?

Several factors go into designing an energy-efficient building that achieves net zero energy goals.

Location

To construct a net zero energy building, you must take several conditions into consideration. The building site, where you are building, the climate and the building’s exposure all have an effect. Among other things, take into account:

• Climate
• Sun
• Wind patterns
• Temperature
• Rain patterns

Orientation

The orientation of the building depends on the success of achieving net zero energy. Certain renewable energy generation mechanisms, like solar panels, work best when the building is facing south.

But factors that conserve energy are also important. Besides harnessing the sun’s energy, you can conserve by orienting your building to take maximum advantage of the shade. In warm climates, this means you’ll need to use the air conditioning less to keep your building cool.

Lighting is another important factor. Lighting systems can account for?almost 25%?of a building’s total energy consumption. Orienting your building to take advantage of natural lighting can reduce that load. Window arrangement and the use of skylights are strategies that can be considered when deciding on a building’s orientation.

You can also situate your building to take advantage of natural breezes. Using natural resources to power your building’s energy systems and reduce energy requirements, will conserve resources at the same time.

Design

Building design is next. Make sure to select the best-insulating materials possible so the building conserves as much energy as possible. Windows (dual- or, better, triple-pane and effectively sealed) can pose a major factor in conserving energy.

Passive strategies?aren’t about energy production. They’re about minimizing energy usage — and maximizing energy performance. In fact, they operate without energy use, which is why they help buildings achieve net zero energy use:

• High-efficiency appliances?require less energy and lighten the overall energy load.
• Low-energy HVAC systems?do the same.
• Air sealing?prevents cooled or heated air from escaping through cracks, often around openings such as windows and doors. This results in less need for air conditioning or heating to maintain climate control.
• Insulation?performs the same function by providing an extra barrier between the interior and exterior of a building. This layer traps heat (in winter) and cool air-conditioned air (in summer) that otherwise might escape through walls, ceilings, etc.

The effectiveness of insulation is rated in R-values. These vary based on the thickness, density, and type of insulation: the higher the R-value, the better. Types of insulation include:

• Fiberglass
• Wool
• Foam boards or blocks
• Cellulose
• Polystyrene
• Polyisocyanurate
• Polyurethane

Ventilation?is particularly important in tropical climates. It’s necessary to replace stale air with fresh air. This can help to moderate internal temperature while reducing the build-up of moisture that can cause mold and bad odors. The energy used to maintain proper ventilation, by using electrical fans, for example, can be reduced significantly by employing natural strategies.

• Architectural design?in new buildings maximizes efficiency and promotes sustainability.

ASHRAE, or the American Society of Heating, Refrigeration, and Air Conditioning Engineers, has created standards that apply to building design. The group, founded in 1894, has 87 active standards and guideline project committees that address some of the following topics:

• Thermal comfort
• Energy conservation in buildings
• Reduction of refrigerant emissions
• Indoor air quality

Renewables

The final step in designing high-performance buildings is determining the most relevant renewable energy sources based on the building. If the building is industrial scale, wind generators might be used on-site rather than off-site. Solar panels might be the way to go for new homes or even ones that can be converted.

Active strategies?reduce energy consumption during the building process through the use of renewable energy strategies, such as:

• Photovoltaics?— Photovoltaics is the direct conversion of light into electric power using semiconducting materials such as silicon. Each solar panel contains numerous photovoltaic cells, which work together to produce electricity.
• Wind power?— Wind is a kind of?solar energy produced by three factors. It’s affected by the sun unevenly heating the atmosphere, irregularities in the Earth’s surface, and the planet’s rotation. The resulting wind turns propeller blades around a rotor, which spins a generator, creating electricity. Wind farms in mountain passes near?San Bernardino?(San Gorgonio Pass) and Northern California (Altamont Pass) contain hundreds of huge propellers.
• Hydroelectric power?— Hydroelectric plants capture the energy of falling water and convert it into electricity. Water flows downhill and is captured by a reservoir behind a dam. This reservoir acts like a battery, releasing water during periods of peak demand to produce power.
• Biomass?— Biomass stores chemical energy from the sun, produced by plants through photosynthesis. It can be burned directly to produce heat or can be converted into renewable liquid and gas fuels. Biomass can be as simple as a log on a fire. It’s like a solar battery, which releases bioenergy.
• Geothermal power?— Geothermal power involves water pressure in the form of steam. Geothermal wells drilled a mile or two underground pump hot water to the surface. There, the pressure drops and the water turns into steam. The steam spins a turbine connected to a generator, producing electricity.
• Solar power?— Sunlight shining on a panel is absorbed by photovoltaic cells in the panel. This creates an electrical charge in response to an electrical field in the cell, producing electricity.
• Solar thermal?— Solar thermal power systems use mirrors to collect sunlight and concentrate it. This raises the temperature until it is high enough to produce electricity. Examples include curved?parabolic troughs, such as those used in the Mojave Desert.

Net zero energy buildings react in various ways to their local electricity grid. Whether the grid is integrated or conventional affects the way it interacts with buildings and strategies (such as renewable energy sources).

• Energy moves between the grid and conventional energy buildings in a single direction. It flows from the grid to the building, utilizing conventional metering.
• Moderately responsive buildings have interactive demand response.
• Buildings that are fully integrated with the grid include passive efficiency features as well as renewable energy production onsite.

Put another way, the two types of ZNE building typologies must work together to optimize grid performance:

• Renewable-oriented (active strategies)
• Efficiency-oriented (passive strategies)

Utilizing both passive and active strategies will prove most beneficial to the relationship between the utility grid and ZNE buildings.

Conclusion

The challenges are significant, but the methods of meeting and overcoming them are known. We just need to accelerate the methods and make them work together to maximize energy efficiency. If we do this for new and existing buildings, we can meet the goals we’ve set for 2030 and 2040. We can even meet those for 2050, as we work to identify new, longer-term goals.

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