Article #159 - About Residential Compliance

Choosing the appropriate approach depends on the complexity and/or uniqueness of the building, and the amount of time and money available for demonstrating compliance. The prescriptive approach allows quick review of the requirements. If these requirements are too restrictive, try a trade-off approach. For example, if the window area of the building exceeds that allowed by the prescriptive approach, a trade-off approach might work. If nontraditional components are used or if energy use trade-off between building systems (e.g., envelope, mechanical) is desired, then use the performance approach.

The different approaches can produce different results. Performance approaches require a higher degree of detail so that an individual building can be designed to exactly meet the energy code requirements. Prescriptive approaches tend to be somewhat conservative and use worst-case default assumptions so the prescriptive packages are applicable to all buildings. Although the prescriptive approach may result in a more energy-efficient building because of its conservative assumptions, this result is not always the case. The prescriptive approach generally does not account for several features that affect energy use, such as the effect of window orientation and external shading on solar heat gain. Trade-off approaches fall somewhere between the prescriptive and performance approaches in both flexibility and complexity.

Over the years, the code has grown to provide different approaches of varying simplicity and flexibility to meet user needs. The simpler approaches are less flexible but are generally easier to use. Some of the approaches have considerable overlap.

The Model Energy Code (MEC) (predecessor to the IECC) and the IECC contain requirements for all three approaches. If your state has adopted any versions of the MEC or IECC directly, you may be allowed to use all three compliance approaches. Check with your local jurisdiction to determine which approaches and compliance tools you can use.

The REScheck software can be downloaded at no cost.

To learn more about the different compliance approaches, checkout the article on the Three Approaches to Residential Compliance .