Posted in Architects
Decoding the 2012 IECC: Understanding Changes in the Context of a Home’s System
It’s been over a year since the International Code Council released the 2012 International Energy Conservation Code (IECC). While adoption has been slow, updates are driving changes in building practices as more states and municipalities consider implementing the new energy standards.
In line with goals set by the Department of Energy, the changes in the energy code seek to achieve 30 percent energy savings over the 2006 code by increasing insulation requirements, addressing air leakage and updating high-efficacy lighting minimums, among other changes.
The updated code includes a number of prescriptive requirements, or examples of how builders can meet the new performance criteria. A number of these prescriptive requirements are designed to address the movement of heat in a building as it relates to energy efficiency. The first—R402.1—deals with specific insulation requirements and the addition of a thermal barrier.
Under the new code, builders in Climate Zones 6–8 are required to install R-5 continuous insulation with R-20 cavity insulation, R-10 continuous insulation with R-13 cavity insulation, or implement an alternative assembly with an equivalent U-factor. Climate Zones 3, 4 and 5(excluding Marine 4) now include prescriptive requirements for R-20 cavity insulation only or R-13 cavity insulation +R5 continuous insulation or insulated siding. These prescriptive requirements may create challenges when installing windows, doors and most types of exterior cladding, and will also require careful consideration in managing moisture in the wall system.
Additionally, the new code outlines prescriptive updates to ceiling insulation requirements in section R402.2. Depending on the climate zone, ceilings with attic spaces requiring R-38 insulation must also have the full height of uncompressed R-30 insulation extend over the wall top plate at the eaves. Climate zones that require R-49 insulation must have the full height of uncompressed R-38 insulation extend over the wall top plates at the eaves. This additional height of insulation over the top of the wall could present challenges particularly for hand-framed rafters. For builders using truss systems, energy heel trusses could offer a means to meet these code requirements. Alternative assemblies that meet specific U-factor equivalents are another potential option.
In section R402.4, the updated code addresses air leakage and overall tightness of the building envelope with a mandatory requirement for a continuous air barrier to be installed in the building envelope. Not only must all breaks or joints in the barrier be sealed, but the code also outlines specific sealing requirements in ceilings, walls, windows, doors, floors, etc.
Once sealed, the installation has to be inspected and approved by a third party, where required by the code official. Finally, the building must be tested and verified as having an air leakage rate not exceeding 5 air changes per hour in Climate Zones 1 and 2, or 3 air changes per hour in Climate Zones 3–8.
The industry is now faced with the need to implement these prescriptive and mandatory requirements within the context of a building system. In future issues, we will discuss various elements of the code in greater detail as we aim to further equip our readers with the tools to make informed decisions as they relate to code changes.
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