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Net-Zero Energy, High-Performance Buildings Program

Summary

Buildings account for 40% of the primary energy consumption, 74% of the electricity consumption, and 39% of the CO2 emissions in the United States. That energy use is associated with more than $200B in expenditures in residential buildings and $150B in commercial buildings. The energy efficiency sector accounts for more than 2.2M U.S. jobs, with about 1 million of those associated with the manufacture, installation, and maintenance of systems for space heating and cooling and water heating. The economic impact of buildings’ indoor environment, however, goes beyond energy costs, as studies report that employees’ annual salaries exceed building operation and rental costs by a factor of 25 and that improving the indoor environment of workplaces could result in productivity increases of $12B to $125B annually. To minimize the costs associated with building energy consumption, to support technical innovation and job growth in the building and HVAC&R industries, and to provide workplaces and residences with indoor environmental quality that improves productivity and well-being, NIST will develop and deploy the measurement science to move the nation towards net-zero energy, high-performance buildings. This program will focus on achieving high performance buildings in a cost-effective manner while maintaining healthy indoor environments. The research program will target the objective of net-zero energy buildings by developing measurement science for 1) reduced building heating and cooling loads, 2)efficient heating and cooling equipment, 3) onsite energy generation technologies such as photovoltaics, 4) whole-building metrics for energy consumption, indoor air quality, economics, and sustainability, and 5) promoting implementation of program results in industry consensus standards, state and local building codes, and best practices to support the building industry.

Description

Illustrated cutaway showing the inside of the Net Zero Energy House
Credit: Building Science Corporation

Objective:
To develop and deploy advances in measurement science to move the nation toward net-zero energy, high-performance buildings while maintaining healthy indoor environments.

What is the problem?
Buildings account for 40% of the primary energy consumption, 74% of the electricity consumption, and 39% of the CO2 emissions in the United States. (i)  Reducing the energy consumption from the building sector poses a national challenge and opportunity, as it will lead to significant financial and job growth of the HVAC&R industries and reduced costs for building and home owners.  To reduce dependence on energy imports and decrease building operating costs, the building industry has embraced the concept of net-zero energy buildings, which are buildings that generate as much energy through renewable means as is consumed by the building.  The goal of reduced building energy use has been documented by leading industry organizations such as the American Institute of Architects (AIA) (ii), the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) (iii), and the National Association of Home Builders (NAHB) (iv).  The movement towards green buildings is a key part of the building industry’s response to this goal, with the global green building market estimated to be over $300 billion by 2023 (v, vi). It is also estimated that 20 % of all new U.S. commercial real estate construction is pursuing green building design, and that commercial building owners and managers will invest $960 billion globally between 2015 and 2023 on greening existing built infrastructure. (vii)

To achieve net-zero and low energy buildings, the building industry will use existing energy-efficient building technologies, develop new equipment and approaches to increase efficiency, and increase on-site generation of energy.  Industry groups including ASHRAE, HVAC&R equipment manufacturers through the Air-Conditioning, Heating, and Refrigeration Institute (AHRI), the American Home Appliance Manufacturers (AHAM), NAHB, and others are all heavily engaged in these efforts.  However, measurement science is lacking in a number of areas for both improving the implementation of existing technologies and advancing new technologies as documented in the “Measurement Science Roadmap for Net-Zero Energy Buildings” (vi), an effort led by NIST to gather research needs from a range of industry stakeholders.  That roadmap reports that improved implementation of existing building technologies can reduce energy consumption by 30-50%, with an additional 50-70% of energy savings from advanced technologies and on-site energy production.  

While energy expenditures are a key operating cost that will be addressed in this program, it is vital to also ensure comfortable and healthy indoor environments for occupants. Annual salaries of employees outweigh energy bills and rental costs by a factor of up to 25 (xii). Increased productivity, even marginally, can yield dividends between $12B and $125B annually in the U.S. (ibid). This research program will also investigate ways to maintain healthy and productive indoor environments while decreasing energy consumption so that buildings continue to meet their intended objectives, i.e., to provide shelter for living, learning, healing, and working. 

What is the new technical idea?
To help the U.S. building industry achieve net-zero energy, high-performance buildings, NIST will focus on four thrust areas.  The first covers whole building metrics, while the final three view the building from a component perspective.  

Thrust 1:  Whole Building Metrics.  The first thrust will address the building as a complete system, evaluating indoor environmental quality, water quality, energy consumption, cost-effectiveness, and overall sustainability of whole buildings. Work in this area will build on that from the other thrust areas and ensure the goal of achieving sustainability and maintaining indoor environmental quality while managing energy usage and economic costs.

Thrust 2:  Building Envelope Load Reduction.  Space conditioning, consisting of heating, cooling, and outdoor air ventilation, is the largest energy consumer in buildings.  In the U.S., it accounts for 40% of primary energy consumption in commercial buildings and 43% in residential buildings. (ix) Space conditioning is required to manage heat loss or gain through the building envelope, unwanted leakage of outside air (e.g., infiltration), and ventilation to control the concentrations of airborne contaminants within the building. The first step in reducing energy intensive space conditioning is by reducing the need for it. NIST is working to minimize this need by evaluating the insulating capabilities of the envelope. Novel methods are continuing to be developed for incorporating airflow into building energy simulation design processes so that improvements to building envelope airtightness can be better accounted for. Lastly, controlling outdoor ventilation in buildings is important as it impacts indoor air quality and energy, and NIST will work on developing control algorithms that can maximize both. 

Thrust 3:  Equipment Efficiency.  Once building loads are reduced, the next step towards net-zero energy buildings is through the use of efficient equipment. Under this thrust, NIST focuses on space heating, space cooling, and water heating, as these end uses are the largest consumers of primary energy in buildings. NIST research will help industry to improve the design and installation of vapor compression heat pump systems for energy efficient buildings, evaluate the effectiveness of the low global-warming potential alternatives to hydrofluorocarbon refrigerants that industry is committed to using, and the performance of alternative methods to distribute air in residential buildings. NIST addresses these equipment issues through partnerships with industry groups including AHAM, AHRI, ACCA, and ASHRAE, as well as other agencies, specifically DOD and DOE. Research will also be conducted on assessing water heating system performance in the field. Closely related to this topic, NIST will merge its expertise in water heating systems with broader issues facing the premise plumbing industry to ensure that efforts to conserve water and energy do not impact water quality or the durability of plumbing systems.  

Thrust 4:  On-Site Energy Generation. After loads are reduced and efficient equipment is installed, the remaining energy must be supplied by on-site generation to meet the goal of net-zero operation. NIST will address measurement science issues associated with photovoltaics, which are currently the predominant means of harnessing renewable energy for on-site building use. The solar industry has experienced tremendous growth in the United States in recent years, with an average annual growth rate of 50 % in the last decade (x) and the employment of over 240,000 workers in 2018 (xi). This growth heightens the need for performance assessment and rating, understanding the physics of new technology, and service life prediction to ensure systems operate as promised and are durable over their expected lives. 

What is the research plan?
The research plan will follow the four thrusts described previously. 

Thrust 1:  Whole Building Metrics. Knowledge of the overall sustainability of buildings and the economics of high-performance buildings will be advanced through the development of online tools for evaluating sustainability. A relatively new research area related to water use and water quality in buildings will continue, with the goal of developing data, models, and guidelines for designing effective plumbing systems to address the increasingly pressing needs of reducing building water usage while minimizing exposure to waterborne pathogens and contaminants. As part of this thrust, indoor air quality knowledge will be advanced by developing new measurement science using the NZERTF as a testbed for understanding indoor chemistry and interzonal airflow.  

Thrust 2:  Building Load Reduction. NIST will aim to minimize the unwanted heat losses and gains through the building envelope by developing reference materials that allow precise evaluation of thermal insulation and by investigating the measurement science that is needed to support the use of advanced insulation systems. NIST will develop the measurement science necessary to determine required ventilation rates by developing reference materials and test procedures that can be used to assess emissions from building products and measurement methods to characterize the most important contributors to adverse indoor air quality. NIST will build upon previous work to integrate the EnergyPlus building energy simulation software with the CONTAM airflow and contaminant transport software by improving the user interface to enable more widespread use of the tool. Novel methods to control outdoor air ventilation in residences will be developed to create strategies for maintaining indoor air quality in a net-zero energy home while maximizing energy efficiency.

Thrust 3: NIST will focus on vapor compression equipment used for space heating, cooling, and water heating. In particular, research will be conducted to provide industry greater understanding of system performance as buildings become more efficient and will address industry challenges in modifying equipment in response to its transition to a new generation of refrigerants. In addition, as building envelopes become more efficient, heating and cooling systems must manage smaller thermal loads, but moisture management and the need to mechanically ventilate buildings impose new demands on the systems. NIST will develop software tools and data sets to support stakeholders in the optimal design, selection and installation of heat pumps and air conditioners in energy-efficient buildings. The industry has committed to adopt a new generation of refrigerants for use in heat pumps and air conditioners. To optimize those systems, designers need to understand the thermodynamic performance limits of the refrigerants and their thermophysical characteristics as they impact the refrigeration process. Alternative refrigerants and refrigeration systems will also play a role in increasing the efficiency of water heating systems, and research will be conducted on two approaches to improving water heating efficiency: the use of CO2 as a refrigerant in heat pump water heaters, and the integration of a water heating system with a ground-source heat pump unit. The safety of these refrigerants is also a significant concern to the industry because many of the identified replacements are mildly flammable, which is a new hazard. Therefore, NIST will develop test methods and data to assess the flammability of these compounds and their mixtures for use by manufacturers in developing efficient and safe equipment.

Thrust 4:  On-Site Generation. NIST will support the increasing use of photovoltaics (PV) through development of techniques to better rate PV performance and generation of the measurement science to assess the service life of polymers used in PV modules. The first effort will focus on decreasing the uncertainty in PV ratings by developing a measurement service for calibrating PV cells for use in test equipment. Additionally, measurement approaches will be developed as part of this effort to assess new photovoltaic technologies that promise higher efficiencies and enable use of PV technologies in new applications. The second effort will provide information and standards on the lifetime of polymers in PV systems through accelerated aging tools and model development that will help assess long-term performance.

Major Accomplishments

Some recent accomplishments for the Net-Zero Energy, High-Performance Buildings Program include:

Created October 27, 2011, Updated April 7, 2021