Assessment of Energy Code Compliance in Western States

Client: Northwest Energy Efficiency Alliance

Project Team: Industrial Economics, Incorporated (IEc), Resource Refocus

Project Date: 2023

Project Summary

Industrial Economics, Incorporated (IEc) and RR are conducting a series of field assessments on behalf of NEEA to quantify the extent to which the energy savings goals of recent residential building energy codes are realized in Idaho, Montana, and Oregon. These research efforts are based on the methodology specified in the Department of Energy’s Residential Building Energy Code Field Study, which quantifies the baseline energy use and savings potential in residential new construction. The RR team is leading the energy modeling and savings calculations which involve developing custom “code-compliant” EnergyPlus models for each state based on PNNL’s residential prototype models. A Monte Carlo sampling approach is used to generate a representative set of possible measure combinations based on data from recently constructed homes.

The studies assesses statewide compliance levels for the following seven key measures:

  1. Envelope tightness (air changes per hour (ACH) at 50 Pascals).

  2. Windows (U-factor and solar heat gain coefficient (SHGC)).

  3. Wall insulation (assembly U-factor).

  4. Ceiling insulation (R-value).

  5. Lighting (percent high-efficacy).

  6. Foundation insulation (including floor insulation, basement wall insulation, crawlspace wall insulation, and slab insulation R-values).

  7. Duct tightness (expressed in cubic feet per minute (cfm) per 100 sq. ft. of conditioned floor area (CFA) at 25 Pascals).

Using data collected on the seven individual code requirements, the study provides estimates of statewide energy code compliance based on the share of the homes that meet the minimum code requirements from an energy consumption perspective.

The results of the Idaho study are discussed below. The Montana and Oregon studies are ongoing.

Idaho Residential Code Compliance Evaluation

Report: Idaho Residential Code Compliance Evaluation Methods and Results

The Idaho study provides insight into 2018 IECC with Idaho amendments code compliance both at a measure and whole home level. Two IECC climate zones are found in Idaho: climate zone 5B cool dry (CZ5) and climate zone 6B cold dry (CZ6). 

Some of the report findings include:

  • From an energy perspective the average Idaho home is estimated to use 8% less energy than a home built to exactly meet the code minimum. 

  • Improving the wall insulation U-factor could realize more than three-quarters of the state's cost, energy, and emissions savings potential. Two key areas for improvement are insulation installation quality (IIQ) statewide and insulation R-value in CZ6.

  • Ninety-six percent of the space heating systems are natural gas furnaces, while 4% are some form of electric. 90% of the domestic hot water (DHW) heating uses natural gas, while 10% is electric.

Graph of observed and code minimum EUIs

Figure 1. Statewide EUI analysis for Idaho

Table 1. Annual statewide savings potential

Figure 2. Wall U-factor

Table 2. Wall U-factor

 

Resource Refocus LLC is a WBE certified business and is listed through The Supplier Clearinghouse. Resource Refocus is also a certified Small Business through the California Department of General Services.

Resource Refocus LLC, based in Berkeley, CA, is a limited liability company registered in the state of California. The firm was founded in 2010 by Anna LaRue and Noelle Cole.