The 2015 IECC keeps the traditional pathways of compliance explained above but introduces the Energy Rating Index path (ERI). The ERI has three main components:
- As with all pathways of compliance, the ERI path requires compliance with all the mandatory provisions of the IECC such as air leakage, duct leakage, ventilation, and air barrier/insulation requirements. This means that the air leakage requirement of 3 ACH50 cannot be traded off.
- The ERI path requires the minimum component insulation levels of the 2009 IECC which means that the R-values and U-values of the 2009 IECC become mandatory. You can add more insulation but you cannot trade off for lower component R-values or U-values.
- The ERI is utilizing a fixed Energy Rating Index to help demonstrate compliance with the code. For now the RESNET HERS Index will be what is used. The House will have to meet or exceed the climate zone specific required Index to be code compliant.
As mentioned before, the structure of the IECC requires that, regardless of the pathway chosen through the code, all mandatory requirements in chapter 4 “Residential Energy Efficiency” must be met.
Confusion often arises due to another heading in the code titled “Prescriptive.” Unlike mandatory requirements, prescriptive requirements describe measures that must be accomplished when utilizing the prescriptive and total UA alternative pathways through the code. Although they are not mandatory for all pathways, the prescriptive requirements are often referenced as they embody best practices and are at time referred to in the mandatory sections.
The “Air leakage” section 402.4 of the IECC is mandatory for both the 2009 and the 2015 IECC. However, there are some significant changes in the 2015 version of the code. First, the 2009 allowed a choice between testing the home to achieve less than 7 ACH (air changes per hour) or a visual inspection utilizing the air barrier and insulation table (when utilizing the simulated performance path both of these options were utilized). The 2015 IECC, alternatively, requires both compliance with the air barrier and insulation table, as well as air leakage testing utilizing a blower door. In addition, the 2015 IECC ramped down the air leakage requirement in Climate zone five to 3 ACH, a substantial increase in house tightness. It introduces a new mandatory requirement to ventilate the house properly utilizing whole house controlled mechanical ventilation. This will be brand new to builders coming from the 2009 unless they were using the simulated performance path where house tightness was often used to trade off R-values and U-values in the envelope. EnergyLogic is seeing that by following the 2015 air barrier and insulation table, which was broken out into separate air barrier and insulation columns for clarification in the 2015 IECC, builders are not having any difficulty meeting the 3 ACH requirements in their single family homes. However, Multi-family projects are often struggling to achieve 3 ACH and additional air sealing measures are often needed.
The air leakage section of the 2015 IECC has a significant addition in section R402.4.4 “Rooms containing fuel-burning appliances.” This section now requires a combustion closet or sealed combustion appliances. The change applies to climate zones 3 through 8 and states that “where open combustion air ducts provide combustion air to open combustion, space conditioning fuel burning appliances, the appliances and combustion air openings shall be located outside of the building thermal envelope, or enclosed in a room isolated from inside the thermal envelope.” When a room is used to isolate the appliances from the conditioned space, the room must be sealed and insulated in accordance with the below-grade wall R-value requirement in Table R402.1.1.
Duct leakage testing is another mandatory section of the 2009 and 2015 IECC and there have been changes in the newer versions of the code. Specifically, the 2009 allowed four possible scenarios for testing of the duct system including total duct leakage testing and duct leakage to outside testing at rough or final. The 2012 and 2015 IECC, written slightly differently, moved away from allowing duct leakage to outside testing and now only requires a total duct leakage test if any portion of the duct system is located outside of the building envelope. This is very clear if a portion or all of the duct work is located in a ventilated attic, for example, but is at times difficult to assess if the duct is located within the building envelope such as ducts in a floor system over a garage or an exterior wall in our open floor plans.
Although the early chapters of the IECC do not correspond directly to field construction of the house, they are important to read and understand as the last of the big changes between the 2009 and 2015 IECC occur outside of chapter 4 “Residential Energy Efficiency.” Chapter 1 of the IECC is titled “Scope and Administration.” This chapter includes information that is required on construction documents most significantly:
- R-values and U-values of the thermal envelope
- Mechanical system design criteria
- Duct sealing, duct and piping installation and location
- Air sealing details
- And section R103.2.1 building thermal envelope depiction. “The building’s thermal envelope shall be represented on the construction documents.”
Chapter 1 also includes section 104 “inspections”. In this revised section of the 2015 IECC a detailed description is given on the type of inspections that are required including footing and foundation inspection, framing and rough-in inspection, plumbing rough-in inspection, mechanical rough-in inspection, final inspections, and re-inspections.
Chapter 2 “Definitions” includes some new terms such as circulating hot water system which was needed to help describe an entirely new mandatory section of the 2015 IECC R403.4.1 “Heated water circulation and temperature maintenance systems.” I did not discuss this in this article as the provisions are only mandatory if a hot water circulation system has been installed. In addition, definitions of terms used in the Energy Rating Index path were added to this chapter.
Chapter 3 includes the addition of a new tropical climate zone as well a better defined requirement that the insulator “shall” provide a certificate listing the manufacture and R-value of installed insulation in each component of the building, as well as, the installed density for wall and attic blown insulation and coverage area, installed thickness, settled thickness and R-value of blown attic insulation. “The insulation installer shall sign, date, and post the certification in a conspicuous location on the job site.” I am highlighting this here as we recently learned that insulation companies are installing wall insulation at different densities to achieve different R-values. It was standard practice to insulate a 2×6 wall with blown fiberglass to an R-23. Now, based on the density of the installed blown in product builders can be receiving anywhere from an R-20 to an R-24. Unfortunately code and quality assurance inspection cannot visually identify the R-value of the assembly. We therefore recommend that builders include language in their scope of work documents requiring the creation and posting of a completed insulation certificate as well as the posting of results from at least 4 density tests per home. This should ensure your installation is meeting your specifications.
Lastly, there are a couple new sections of the code that should be touched on.
- Chapter 5 is a new chapter that explains how the energy code “control (s) the alterations, repair, addition and change of occupancy of existing buildings and structures.”
- For the first time the IECC will have two new appendices. The first involves recommended procedures for worst-case testing of atmospheric venting systems (combustion safety testing). The second is a solar-ready provision for detached one and two-family dwellings. Appendices are not mandatory unless an adopting jurisdiction makes it so.
So after analyzing the 2015 IECC you will notice that the actual impact to energy efficiency is minor compared to the changes introduced in the 2012 IECC. If jurisdictions are moving to a new energy code it will only impact you if that jurisdiction is moving from the 2009 or earlier version of the IECC and if a builder has not had any experience working in a jurisdiction that is currently on the 2012. The 2015 IECC truly represents a break in the process of ramping up requirements and efficiencies to make the code more stringent. It is a better written version of the 2012 IECC which added a unique compliance path utilizing the Energy Rating Index.
Time will tell if this is a trend in the code development cycle or not.
Principal and Director of Builder Relations