Model Energy Code Thermal Envelope Compliance Guide for 1 and 2 Family Dwellings
March 31, 2005
The purpose of this guide is to help builders and building officials determine compliance with the 1989 and 1992 editions of the CABO Model Energy Code (MEC). The MEC was designed to help architects, designers, and builders increase energy efficiency and realize the potential for energy savings in new homes. It has three basic approaches that can be used to satisfy the goal of designing and constructing and energy conserving structure: (1) Component Performance, (2) Systems Analysis, and (3) Acceptable Practice. The Component Performance approach is the focus of this guide. It sets a limitation on the overall thermal transmittance (Uo) of each building envelope component (such as walls, roof/ceiling, and floors). By establishing a limitation on each envelope component, the designer can use a step-by-step method to determine compliance. The guide includes an application worksheet to allow users to compare specific envelope component designs with those that comply with the MEC. Also included are interpretive requirement tables, which list hundreds of wall/window combinations to show the compliance options for meeting the exterior wall criteria. The tables indicate the thermal resistance of the opaque wall assembly as a function of both the percentage of open area wall (which include windows, doors, and sliding glass doors) and the thermal resistance of the glazing type selected. There are also instructions and a worksheet for determining compliance where one or more component assemblies are below code requirements and trade-offs between designs and requirements are necessary. The guide concludes with an example of how a builder or designer would use either the applications worksheet or trade-off worksheet to verify MEC compliance.