DOE Field Study Methodology Provides States with Better Data on Building Energy Codes

June 7, 2018

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Model building energy codes can save homeowners and business $126 billion in energy cost savings between 2010 and 2040 – but only if buildings are built to code. Construction practices vary significantly across the United States and there is often a shortage of empirical data on how industry standards are applied in the field. The Building Technologies Office’s Building Energy Codes Program (BECP) has supported research teams that gather baseline construction practices and trends across states, helping states and others with a vested interest in energy efficiency and consumer savings better understand the opportunities, challenges, and savings that can result from the building energy codes they’ve already enacted.

2014 FUNDING OPPORTUNITY: PILOT PROGRAM AND METHODOLOGY

In 2014, BECP awarded funding to eight research teams to test a pilot version of a methodology to assess baseline energy efficiency in new single-family residential buildings and quantify the related savings potential. The original methodology was developed by Pacific Northwest National Laboratory (PNNL) for BECP to assist states as they assess energy efficiency in residential buildings and implementation of their building energy codes – as well as to target areas of improvement through energy codes and broader energy-efficiency programs.

Researchers conducted pilot studies in Alabama, Arkansas, Georgia, Kentucky, Maryland, North Carolina, Pennsylvania, and Texas. The methodology outlines procedures for sampling, data collection, and subsequent analysis, and provides guidance on how to implement a successful study. PNNL identified individual key energy-efficiency measures with the largest direct energy impacts: envelope air tightness, window solar heat gain coefficient (SHGC) and U-factor; wall insulation; ceiling insulation; lighting; foundation insulation; and duct leakage. Since the initial pilots were commissioned, several additional states followed in funding similar studies of their own based on the DOE methodology – over 20 states have used the approach to date.

Using the methodology, states, utilities, and others are able to gather insight on trends surrounding key technologies and efficiency measures as observed in real homes. All results are statistically valid at the statewide level (or other specified region such as a utility service territory), and are based on a single site visit to ensure confidentiality. Findings vary between states, but overall, homes are using less energy than would be expected based solely on the prescriptive codes in the states analyzed.

The study findings also indicate that some key measures are met more successfully than others. For example, the vast majority of window u-factor observations across states met or exceeded state code requirements, a trend that was observed across all states and climates studied. Similarly, cavity wall insulation almost always exactly met the prescriptive (R-value) requirement, although there was generally room for improvement in terms of installed quality. Envelope airtightness was commonly observed in the range of 5 to 7 air changes per hour (ACH50), even in states with no explicit testing requirement. Lighting observations were much less consistent, commonly ranging as widely as 0 to 100% high efficacy. With more data, a better understanding of these trends and patterns can be gained – which will help further capture typical construction practice and associated savings opportunities.

Through PNNL, BECP has continued to provide support to states studying the implementation of their building energy codes. BECP provides technical assistance to states using the DOE methodology, providing sampling plans, resources, and analysis to states employing the approach and committing to having their findings incorporated into the public dataset. This significantly reduces the burden of conducting such a study and helps ensure consistency and comparability across states.

NEXT STEPS

The data from these pilot studies portrays baseline construction practices and trends across the United States, including the market prevalence of key building technologies and efficiency measures, as installed in the field. DOE recently published an updated methodology based on insight gathered through the pilot program. States, utilities, and others conducting similar studies are urged to follow this guidance in conducting future studies reviewing the impact of their codes and broader energy-efficiency programs.

Additionally, BECP is conducting a study of commercial buildings and multifamily buildings to provide a broader look at building energy codes and construction in the field.