Energy Code Compliance for Low Slope Reroofing Projects

By Robert G. Barfield, AIA, NCARB

August 12, 2014


Although the Energy Conservation Code (Energy Code) has been a part of the International Code Council’s (“ICC”) family of building codes since its establishment in 2000, it is one of the least understood and least enforced sections of codes. Renewed interest in Code requirements is occurring due to use of sustainable construction methods, the focus on energy that is consumed by our built environment, and the incorporation of LEED (“Leadership in Energy and Environmental Design”) requirements into new construction.

The Energy Code, based upon American Society of Heating, Refrigeration, and Air Conditioning Engineers (“ASHRAE”) ASHRAE 90.1 requirements, can become especially difficult to navigate during the design of additions, alternations, renovations and repairs of existing buildings. An example of this occurs with what otherwise seems to be a simple low slope roof replacement on an existing commercial building. Dependent upon the climatic zone in which the building is located, the roof will be required to meet a value ranging from R-20 through R-35 of continuous insulation above the roof deck.   This requirement is in general to be enforced even on projects that involve only a reroofing

Following are just three introductory scenarios to highlight the considerations and issues which may be encountered for reroofing projects under the requirements of the Energy Code, as it relates to existing commercial buildings. The case studies are the entire same roof configuration of an existing 20 year old building located in Climatic Zone 3, which according to the 2012 Energy Code, requires the insulation to meet an R value of 20. There is currently only one layer of roofing installed on the building.

Case Study 1

For the first case study, the Owner has voluntarily elected to add an additional layer of roofing on top of the existing roof. Since neither the existing roof decking nor the insulation will be exposed during the roofing process the owner is exempt from the requirements of the Energy Code. However, when choosing to proceed in this manner, one must also be aware that Section 1510 of the International Building Code (“IBC”) states that no more than two roofs can be installed on any building. Therefore, under current codes when the Owner needs a new roof in the future, both the original roof and new reroof will need removed and requirements of the current Energy Code must then be met.

Case Study 2

In the second case study, the Owner discovers that the roof is leaking however the underlying roofing materials are generally not damaged. The Owner decides that the leaks can be addressed by recovering the existing roof with a new roof membrane, and is interested in adding additional insulation to the roof assembly in an attempt to reduce energy costs. The best solution in this case is to provide additional insulation on top of the existing roof and then install the new roof.

Again, because neither the existing insulation nor the roof deck will be exposed during the project, the Owner is not required to meet the R value requirements of the Energy Code and can limit the R value as the project budget or other constraints will allow. As in Case Study 1 future considerations of roof replacement will be based on the building then having two roof membranes upon it.

Case Study 3

For the third case study, the Owner discovers that the roof is leaking and the underlying materials are water soaked and deteriorated, requiring replacement to the roof deck. Since the roof insulation and deck will be exposed during the process, the new assembly is required to meet a minimum of R-20 as established in the Energy Code.   However, windows in walls surrounding the roof area prevent installation of additional thicknesses of insulation above the roof deck to achieve the required R-value, and the Owner must now add insulation below the roof structure of the building to meet the required R-value. Although this will add significant cost to the project, it is required per section C101.4.3 of the Code.

If the owner believes that this requirement is an unnecessary and undue hardship then they may request a variance from the local code Authority Having Jurisdiction (AHJ), as the Energy Code is not intended to require significant and extensive modification to an existing building. Variances however are not explicitly addressed in the Code, are at the discretion of the local code officials, and are therefore not a guaranteed solution to the issues this example presents


The Energy Conservation Code requires that all of the parameters and their potential ramifications are fully understood and considered before the project begins.

Interest in sustainable materials, construction methods and energy consumption in the built environment has led many authorities to enforce the ICC Energy Conservation Code, and several states have created their own energy guidelines and codes. Although energy conservation is a needed and welcomed change, the enforcement of these codes has created new challenges for design professionals and commercial low slope roofing contractors involved in these reroofing projects. No longer can a low slope roof simply be “replaced” with new versions of the same assemblies, based on the assumption that an existing structure is “grandfathered” and exempt from the currently enforced codes. It is the responsibility of architects, engineers, and roofing contractors to be aware of the requirement of the Energy Conservation Code, and properly advise building owners of the considerations and requirements of new roofs for their buildings.



  1. ASHRAE 90.1
  2. 2012 International Building Code
  3. 2012 International Energy Conservation Code


One Response to “Energy Code Compliance for Low Slope Reroofing Projects”

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