Codes and standards for energy conservation

R-value misperception and the need for improving understanding
This article has identified several factors that may be very confusing to a building designer trying to determine the appropriate insulation R-values required by code.

First, the thermal value requirements of IECC or IgCC may differ from similar requirements in ASHRAE 90.1-2010 or ASHRAE 189.1-2011, which are intended to be functional equivalents to one another.

Next, determining IgCC thermal-value requirements is complicated, as several steps must be taken to arrive at the appropriate insulation R-values. Finally, proper determination of roof and wall R-values requires additional understanding of the specific type of roof and wall assembly involved, as well as the correct climate zone for the project. (Figure 8 offers a color-coded illustration of the country by zone.)

To improve understanding of these confusing and complicated prescriptive R-value requirements, the Center for Environmental Innovation in Roofing (CEIR), collaborating with PIMA, has published an easy-to-use resource for building designers. The Roof and Wall Thermal Design Guide provides a reference tool to help building designers make the best roof and wall insulation decisions for both new and existing buildings. (Click here to download a free copy.) It specifically addresses the complexity of different prescriptive roof and wall thermal values in the 2012 I-Codes by providing an organized, step-by-step approach to determining the climate-appropriate R-value for a limited number of common roof or wall assemblies.

Step one: Select the climate zone
In addition to an illustrated map of the United States, the guide provides a link to detailed county-by-county climate zone information maintained by DOE’s Pacific Northwest National Laboratory (PNNL).

Step two: Select the roof or wall assembly
The guide provides prescriptive R-value information for major roof and wall assembly types referenced in the I-Codes. This includes roofs with insulation above the roof deck along with wood-framed walls and metal-framed walls.

Step three: Select the model code path
The guide provides separate R-value tables for 2012 IECC, 2012 IgCC, ASHRAE 90.1-2010, and ASHRAE 189.1-2011.

Step four: Look up the R-value
After the appropriate R-value table is located, the correct R-value may be determined by cross-referencing the relevant I-Code/ASHRAE standard with the appropriate climate zone.

Limitations of the guide
The CEIR and PIMA Roof and Wall Thermal Design Guide achieves its simplicity by narrowly focusing on one aspect of the I-Codes, while not addressing many other important requirements. The specific prescriptive thermal values for wall and roof assemblies provided by the guide are required only if the energy efficiency of the building is not determined using approved energy modeling software.

Thus, many wall and roof assemblies must incorporate structural, wind, and seismic design requirements not shown in the simple illustrations of this guide. The guide also does not cover other important thermal design requirements for roofs and walls, including use of ‘cool’ roof surfaces in the warmest climate zones or use of roof and wall vapor barriers in northern climates. In addition to a tight focus on only prescriptive R-values, the guide also concentrates strictly only on the most common types of roof and wall assemblies used in conventional commercial building design.

Another limitation of the guide is these codes and standards must be adopted by state and local jurisdictions—typically via legislative statute or a mandated code-adoption process. While some states may have adopted a version of the 2012 I-Codes, it is usually best to use the most up-to-date design information when designing a new building or renovating existing buildings. Further, each state and municipality adopting the I-Codes may include revisions or amendments to the code, which can change the prescriptive R-value requirements shown in the guide.

Some states and municipalities also may adopt only the ASHRAE version of the code as the prevailing standard. As well, the newer above-the-code standards of 2012 IgCC and ASHRAE 189.1 may be adopted by states and municipalities to apply only to certain projects, such as public facilities rather than private buildings.

The specific requirements of any individual state or municipal code jurisdiction is obviously beyond the scope of such a basic guide. However, a very useful online reference for state and local code requirements is sponsored and maintained by the non-profit Building Codes Assistance Project (BCAP). Its Online Code Environment and Advocacy Network enables designers to select any state from an interactive U.S. map and discover which model code has been adopted, what amendments (if any) have been enacted, and what procedures and timetable are followed to update the code.

Conclusion
Perhaps the biggest dilemma in using the I-Code references is it is so difficult to research and obtain the actual R-values of the roof systems available in today’s marketplace. This is another limitation of using this type of process to determine actual R-values. The development of a more up-to-date and accurate guide listing the actual R-values of all the individual roof and wall assembly components would yield a better benchmark to begin the process of using the guide with measured confidence.

It may be a difficult process to understand the methods used to establish the true R-values and U-values of the different codes and standards. With hope, a neutral agency or impartial party will develop an accurate material list of all the individual components important to aid in the process of determining more accurate results. The various testing methods described in this article are in place, allowing others to help to reduce the effects of global warming, which will not happen on its own.

It is also critical to become more aware of the consequences of not following through with improving on the accuracy of the methods used to perform these calculations—which, in turn, determines the best practices in our generation’s effort to get global warming and energy consumption under control. A sufficiently well-funded agency or a group of individuals who have the technology to perform this work on a larger scale is needed. This way, in the best-case scenario, the industry can commit its advanced capabilities to slowing down the detrimental fallout of global warming and energy consumption.

Anthony Katona, CDT, is the president of Alliance Roof Consultants Inc., and has been providing professional services as a building envelope and commercial roof consultant since 1999. With construction experience spanning nearly 30 years, he has extensive experience in building envelope and commercial roof consulting, along with general contracting. Katona has served as a member of the Editorial Advisory Board of The Construction Specifier. He can be reached at alliancerc@verizon.net.