Energy Measurements for Existing Residential Buildings Project

Summary

According to the most recent national census data, the median year in which owner-occupied homes were built in the U.S. is 1976¹. Furthermore, housing starts have declined dramatically since 2005². Considering that most of the country's residential building stock is not new, and that residential buildings use approximately 22% of the total energy consumed in the U.S., this research project addresses the need to improve the measurement science required to improve the energy efficiency of existing homes. The aim is to reduce the uncertainties in tools and techniques that are currently used to make energy-use predictions in this sector, and the approach is two-fold: (1) establish a test method to assess the efficacy of commercially available systems that provide energy consumption feedback to building occupants and (2) standardize the implementation of energy audits and the process by which retrofit measures are recommended to homeowners.

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[1] U.S. Department of Housing and Urban Development 2011 American Housing Survey. http://www.huduser.org/portal/datasets/ahs.html

[2] DOE Energy Efficiency Trends in Residential and Commercial Buildings. August 2010. http://apps1.eere.energy.gov/buildings/publications/pdfs/corporate/building_trends_2010.pdf

Description

Objective: To improve estimates of residential whole-building energy consumption by 2014 through characterization of uncertainties of tools used in providing energy feedback to building occupants and selecting retrofit options to improve the performance of existing buildings.

What is the new technical idea? The new technical idea is to assess the uncertainty and measurement errors in approaches to determine whole-house energy consumption. As homes approach net-zero operation, examination of the house as a system is necessary because interactions between components become more important as overall energy use decreases. Information from these measurement approaches can aid occupants in making decisions regarding energy use on a daily basis or in making asset-based improvements on their homes to save energy in the long-term.

Researchers studying residential energy use and occupancy behavior assert that the "lack of awareness and information on energy consumption and cost" is one of three major barriers to energy efficient behavior³ and estimate that direct feedback of energy consumption information to occupants can lead to energy savings of up to 15%⁴. NIST will evaluate commercially-available residential energy monitoring systems (REMS) for electricity and will develop metrics and a test method to quantify measurement accuracy and communication performance so commercial products provide effective information.

In recent years, federal and state programs, as well as utility companies, have provided incentives for homeowners to obtain energy audits. Through a quick series of assessments and observations, auditors recommend improvements to a home and often provide estimates of savings in utility bills should those improvements be implemented. Recent results from NIST-sponsored studies have suggested that there can be substantial variation in these recommendations even when auditors use the same methods, suggesting that there is room to improve standards and guidelines for the auditing process. The idea pursued in this project will assist standards groups in identifying gaps in their auditing standards and in implementing quality control by formalizing a procedure to implement a round-robin program to identify variations in recommendations and estimates of potential energy savings. The procedure will be implemented into a guideline for use by standards developing organizations or financial sponsors of large retrofit efforts, such as utilities.

What is the research plan? In FY13, NIST developed a testbed to evaluate REMS systems with single-point meter measurements as well as those that employed distributed sensors. The testbed consisted of a series of small appliances that served as typical household loads as well as a single load emulator to simulate larger appliances. In FY14, NIST will complete development of a building load emulator that will include complete residential electrical service and utilize a series of programmable loads that simulate disaggregated buildings loads from the small (i.e., plug loads, lighting, and small appliances) to the large (i.e., water heating and HVAC systems). A set of metrics will be developed to assess REMS accuracy (error rate), communication performance (frequency of data transmission, protocol type, package delay, package error rate), and ability to disaggregate consumption among different end uses as a means of labeling these systems and characterizing their capabilities. Load schedules will be implemented on the building load emulator to evaluate these metrics. By the end of FY14, NIST will develop and validate a whole home load simulation and comprehensive test procedure to grade REMS systems.

To assess the variability in recommendations from energy audits and determine gaps in existing standards and protocols, NIST will work towards producing a guideline document for the implementation of energy audit round robins for quality assurance. In FY12 and FY13, a NIST grantee executed a series of round robin studies, where several home performance contractors trained to implement a specific audit standard reviewed the same home and gave their assessments and retrofit recommendations. Differences in the ways that the audits were conducted contributed to variability in results. For example, use of different tools or approaches to measurement affected results. In FY14, NIST will focus on providing the home energy audit standards community a guideline document that will allow organizations like Residential Energy Services Network (RESNET) and the Building Performance Institute (BPI) to implement their own round-robin-like studies to reduce variability in their audits and to identify additional needs for standardization. NIST will lead a working group with home energy rating organizations and government entities interested in contributing input into this guidance document. The measures called for will be validated in a larger round robin to take place at the Affordable Comfort, Inc. (ACI) National Home Performance Conference in April 2014.

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[3] World Business Council. Energy Efficiency in Buildings. http://www.c2es.org/docUploads/EEBSummaryReportFINAL.pdf

[4] S. Darby. The Effectiveness of Feedback on Energy Consumption: A Review for DEFRA of the Literature on Metering, Billing and Direct Displays. April 2006. Environmental Change Institute University of Oxford.

Major Accomplishments

Outcomes:

• Phase II SBIR grantee developed commercial residential energy monitoring system.
• Testbed created to assess energy monitoring systems.
  

Standards and Codes:

Results of sensitivity analyses of residential buildings models will be shared with ASHRAE Standards Committee 90.2 and a proposed ASHRAE committee on high performance, green residential buildings. Results of energy audit analysis will lead to modifications of standards and guidelines developed by organizations such as the Residential Energy Services Network (RESNET) and the Building Performance Institute (BPI). Test method for residential energy monitoring systems and results of its evaluation will be disseminated to organization deemed most appropriate. Candidate organizations include ASHRAE, ASTM International, and IEEE.