Analysis of Code-Compliant Construction in Texas Based on Texas Building Energy Performance Standards (TBEPS)

This paper presents a detailed technical analysis comparing the stringency of the Texas Building Energy Performance Standards (TBEPS), based on Chapter 11 of the 2009 International Residential Code (IRC) for residential construction and Chapter 5 of the 2009 International Energy Conservation Code (IECC) for commercial construction, to the recently published editions of the IRC and IECC: 2012 IRC for residential construction and 2012 IECC for commercial construction. A series of simulations were performed using the Laboratory’s single-family and large commercial office building simulation models based on the DOE-2.1e program and the appropriate TMY2 weather files for three counties representing three 2009 IECC and 2012 IECC Climate Zones across Texas: Harris County for Climate Zone 2, Tarrant County for Climate Zone 3, and Potter County for Climate Zone 4. The analysis determined that the residential provisions of 2012 IRC are more stringent than the 2009 IRC that used the relevant 2009 IECC residential provisions, which is one of the two paths to comply with the 2009 IRC per Section N1101.2 of the code. The annual total source energy savings of the 2012 IRC ranges from 16.3% to 21.4% with the performance path and from 14.3% to 20.1% with the prescriptive path, depending on the climate zone and the heating system type of a house. The analysis for large office buildings also determined that the commercial provisions of 2012 IECC are more stringent that the 2009 IECC. The annual total site energy savings of the 2012 IECC ranges from 7.3% to 11.6% based on site energy use and from 4.1% to 7.0% based on source energy use, depending on the climate zone. 1 Present address: School of Architecture and Planning, The Catholic University of America, Washington, DC. 2 The energy efficiency provisions of the 2009 IRC are adopted as the energy code in Texas for single-family residential construction and become effective on January 1, 2012. Meeting the requirements of the 2009 IECC is one of the compliance options of the 2009 IRC per Section N1101.2 of the 2009 IRC. INTRODUCTION In 2007, the 80 legislature mandated the Energy Systems Laboratory (Laboratory) to take part in Texas rule-making process. As detailed in the Health and Safety Code, Chapter 388., Texas Building Energy Performance Standards (TBEPS), Sec. 388.003 (b-1), the Laboratory is required to submit written recommendations to the State Energy Conservation Office (SECO) on whether the energy efficiency provisions of the latest published editions of the International Residential Code (IRC) or the International Energy Conservation Code (IECC) for residential or commercial energy efficiency and air quality are equivalent to or more stringent than the provisions of editions previously adopted as the TBEPS. This paper presents a detailed technical analysis comparing the stringency of the current TBEPS, based on Chapter 11 of the 2009 IRC for residential construction and Chapter 5 of the 2009 IECC for commercial construction, to the recently published editions of the IRC and IECC: Chapter 11 of the 2012 IRC for residential construction and Chapter 4 [CE] of the 2012 IECC for commercial construction. The analysis used the relevant 2009 IECC residential (Chapters 1-4) provisions, which is one of the two paths to comply with the Chapter 11 of the 2009 IRC per Section N1101.2 of the code 2 . The residential provisions in Chapter 11 of the 2012 IRC are identical to the 2012 IECC. For the commercial comparison the analysis used relevant provisions in the 2009 IECC for large office commercial buildings. 3 The commercial sections of both the 2009 and 2012 IECC include provisions for several building types. However, for the purpose of this analysis only one building type – the large office building was selected. 4 In addition to the commercial simulation analysis described in this paper, a more concise desk-check was performed at the Energy Systems Laboratory comparing the all commercial provisions in the 2012 IECC with the corresponding provisions in the 2009