This article was originally published in the March/April 1996 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.


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Home Energy Magazine Online March/April 1996

Making Sense 
of the 
Model Energy Code

by Stephen Turchen and Craig Conner

Stephen Turchen is a mechanical engineer in the Office of Codes and Standards at the U.S. Department of Energy, and Craig Conner is senior research scientist in the Building Energy and Standards Program at Pacific Northwest National Laboratories.


Newly accessible thanks to user-friendly software, the Model Energy Code can help builders both design houses that qualify for federal financing and market their houses' energy efficiency.


Within the past 18 months, several states and local jurisdictions have adopted the Council of American Building Officials' (CABO) Model Energy Code (MEC) as their building code for energy-related requirements. Figure 1 illustrates locations that have adopted the MEC. Moreover, the Building Officials and Code Administrators Incorporated (BOCA) has referenced only the latest MEC in the 1996 BOCA National Building Codes.

Figure 1. Locations using the model energy code.

Whether a state has adopted it or not, the MEC applies to houses financed through the Federal Housing Administration (FHA), the Department of Veterans Affairs (VA), and the Rural Economic and Community Development (RECD, formerly Farmers' Home Administration). Loans received from or guaranteed by these agencies require that the financed house comply with the MEC. In a speculative housing development, some builders may choose to build all homes to at least MEC levels to preserve the option of getting financing from any of these sources.

Since the energy crisis of the 1970s, many states have developed their own energy codes (examples include New York, Washington, Oregon, California, and Florida). Because the MEC was referenced in both the National Affordable Housing Act of 1990 and the Energy Policy Act of 1992, more and more states have begun using the code as a reference, or adopting it outright. Reasons vary:

  • Some states and local jurisdictions have found maintenance and support of their own code burdensome.
  • Some are attracted to the support materials and training available for the MEC (see MEC Compliance Materials).
  • In some cases, the organizations that supported the existing code are being eliminated or downsized, which may lead to the use of a nationally supported code.
  • The Energy Policy Act of 1992 requires states to consider updating their code if it does not meet or exceed the MEC.
  • Many home builders like the idea of meeting the residential energy requirements for an FHA, VA, or RECD loan at the same time as they meet their state or local energy code. Most builders dislike having to meet two different energy codes to get these loans and their local building permit.

The MEC allows for insulation tradeoffs between walls, ceilings, and floors.

The good news for builders is that the MEC can also be used as an effective marketing tool. Energy efficiency is one of the desirable features on home buyers' want lists. To the extent that a new home competes with the resale market of existing homes, homes built to the MEC are usually more energy-efficient. Builders can market MEC homes by pointing out anticipated savings on utility bills and increased comfort, or by citing MEC compliance as an indicator of quality. If the new home is financed via an energy-efficient mortgage, the buyer can qualify for a larger loan. This can allow the builder to include amenities in the home, such as upgraded cabinets, that the buyer could not have afforded otherwise.

What Does the MEC Require? The MEC contains energy-related building requirements applying to one- and two-family homes as well as low-rise (three stories or less) multifamily buildings. The MEC applies only to new buildings and additions to existing buildings.

The MEC's major focus is on building envelope insulation, including the windows. The MEC requires insulation on ceilings, walls (including basement walls), and floors, and around slabs. The amount of insulation required varies with the climate-the more severe the climate, the more insulation is required. Window energy efficiency requirements also increase with severity of climate. A Climate-Specific Code shows some sample insulation and window levels that meet the MEC requirements.

MEC Compliance Materials
The Model Energy Code (MEC) allows builders a great deal of flexibility in their building designs. However, flexibility and simplicity are not always easy to provide in the same code. Many builders and code officials have complained that the MEC is difficult to use. Fortunately, code compliance materials are available to help builders and code officials make sense of the code. Most builders and code officials will find these compliance materials much easier to use and understand than the MEC itself. (Those wishing to use the actual code can order a copy from CABO at 703/931-4533.)

The U.S. Department of Energy (DOE) has developed a line of materials called MECcheck, designed to facilitate use of the code. The MECcheck materials quickly explain how to comply with the MEC, simplify (or eliminate) calculations, and provide forms for submission to the building department. Included with the materials are a compliance and enforcement manual for all the MEC requirements, prescriptive packages, and easy-to-use software. The prescriptive packages offer a choice of packages listing insulation and window requirements. Either the software or a pencil-and-paper worksheet can be used to figure trade-offs.

The MECcheck materials are available from DOE's Energy Standards hotline (800/270-CODE) for a modest cost. The U.S. Department of Housing and Urban Development (HUD) also provides the MECcheck materials for the 1992 MEC. Contact HUD User (800/245-2691; order documents numbered ACCN-HUD6783, ACCN-HUD6784, and ACCN- HUD6785). Several states (such as Utah and Arkansas) provide MECcheck directly to state residents through training programs and other channels. Training materials are also available from DOE to help those who want to train on the MEC using the MECcheck materials (800/270-CODE). 

Other organizations also offer compliance tools. The MEC Thermal Envelope Compliance Guide is a pencil-and-paper trade-off worksheet that can be obtained from the North American Insulation Manufacturers Association (NAIMA, 703/ 684-0084). REC/Design is a software tool available from the Architectural Energy Corporation (303/444-4149). These and other compliance materials generally deal only with the insulation and window requirements. If you use them, remember that the additional basic requirements must also be met.


All of the insulation and window requirements can be traded off (varied), so long as the resulting building does not have a greater average heat loss (conductivity x area, or UA) than a similar building constructed to meet the MEC requirements. For example, ceiling insulation exceeding the MEC-required level can be traded off against less floor insulation than is required. Several compliance options can be used to demonstrate such trade-offs. For instance, a builder accustomed to using 2 x 6 wall construction can get relatively high wall R-values that can be traded off against lower insulation levels in the basement or a larger window area. (The MEC has no inherent limit on window area.) Simplified software products that allow trade-offs and demonstrate compliance may offer the best combination of simplicity and flexibility.

A whole-building energy analysis can be used to show energy use equal to that of an MEC-compliant home; however, this approach is complex and is seldom used. Before trying such an approach, builders should check with their local building department to be sure that it will be accepted.

In addition to the MEC insulation and window requirements, there are basic criteria that must be met regardless of which envelope compliance approach is used (see Figure 2). These include:

  • Sealing the building envelope to restrict air leakage (caulking, sealing, and weatherstripping at all penetrations and joints).
  • Installing vapor retarders in most climates.
  • Identifying materials used for compliance (such as insulation R-values) on plans, specifications, and/or directly on materials in the residence.
  • Installing temperature controls (separate adjustable controls for each HVAC system in single-family homes and for each multifamily dwelling unit).
  • Insulating and sealing ducts in unconditioned spaces.
  • Insulating pipes for hydronic heating and circulating hot water systems.
  • Installing separate electric meters for each unit in a multifamily dwelling.
  • Installing heater switches, covers, and time clocks for swimming pools.

Figure 2. In addition to insulation levels and window types, the MEC requires the measures shown above.
Common Questions about the MEC So how does the MEC affect design, permitting, and construction? Let's look at some typical questions and their answers.

Who needs to comply? The MEC requirements apply only to new construction and additions to existing buildings. In these cases, builders should demonstrate compliance with the MEC if it has been adopted by their state or local jurisdiction. Builders also need to comply with the MEC if they want their homes to qualify for mortgages from the FHA, the VA, or the RECD.

What's the easiest way to comply with the MEC? Some builders don't have the time or the desire to consider insulation and window trade-offs. Using the compliance materials, they can choose from a list of insulation and window levels (referred to as prescriptive packages or options). Some compliance materials offer a simple table of prescriptive packages for the climate zone (see Figure 3). Users can choose a package of insulation and window requirements from the table. Each package specifies insulation levels, glazing areas, glazing U-values, and sometimes heating and cooling equipment efficiency. The builder must meet or exceed all the requirements it lists to achieve compliance. Few calculations are required.

What about trade-offs? The prescriptive requirements may not be quite appropriate for a particular project, or it may be cheaper to do it another way. In this case, builders can demonstrate compliance by using the trade-off approach. Users can trade off insulation and window efficiency levels in different parts of the building. They can trade off ceiling, wall, floor, basement wall, slab-edge, and crawlspace wall insulation; glazing and door areas; and glazing and door U-values.

Figure 3. MECcheck prescriptive package approach.

The local building department may specify a methodology for demonstrating compliance using a trade-off method. Several organizations, such as the U.S. Department of Energy (DOE) and the North American Insulation Manufacturers Association (NAIMA), have developed compliance materials that can be used to do trade-off calculations.

Documentation. The MEC requires that materials used for compliance (such as insulation) be noted on the plans, specifications, or other attached compliance documentation. The local building official may have a required form for submission. The MECcheck materials and NAIMA's Thermal Compliance Guide both include forms for this use.

Build It Right Assuming that (1) the building is designed in accordance with the MEC, (2) the relevant design features are adequately noted on the documentation submitted to obtain a building permit, and (3) the plan reviewer has validated the claim of compliance, the only remaining hurdle to building a quality MEC house is to build it to the approved plans and specs.

The building department may inspect to verify the energy-conserving features. While numbers and types of inspections vary widely from jurisdiction to jurisdiction, knowledgeable departments try to incorporate energy inspections into their normal regime. The following list gives a sampling of features for which the inspector may check:

  • Wall, ceiling, floor, slab-edge, and basement wall insulation are properly installed and meet required R-values shown on plans.
  • Glazing and door U-values meet requirements shown on plans.
  • Glazing area is as shown on plans.
  • Penetrations and joints are caulked, sealed, and weatherstripped.
  • Duct insulation is installed and meets required R-values shown on plans.
  • Ducts are sealed.
  • Vapor retarder is installed (where applicable).
  • HVAC and water heater equipment maintenance information is left with the home.
A Climate-Specific Code
The envelope requirements for an MEC-compliant home vary by climate. Insulation levels for a typical home with a 15% window area are shown below. The three cities were chosen to illustrate the range of MEC insulation and window requirements in varying climates. These insulation levels are not the only way to comply-builders can trade off insulation levels among building components.

  Houston, TX Kansas City, KS Madison, WI
Heating Degree Days 1280 4710 7860
Ceiling R-value R-19 R-30 R-38
Wall R-value R-13 R-13 R-19
Floor R-value R-13 R-16 R-19
Basement Wall R-value R-6 R-9 R-12
Slab Perimeter R-value None Required R-7 R-18
Glazing U-value 0.65
(double-pane with thermal break)
(double-pane, vinyl or wood frame, with argon or low-e)
(double-pane, vinyl or wood frame, with argon or low-e)

Ask the local building department for additional information about its inspections.

MEC in Perspective Although the widespread adoption of the MEC is definitely a boon for energy efficiency, builders should remember that it represents a minimum building standard. There are many cases when additional conservation measures can help sell a house, because the builder knows how the house will be used, or because local energy prices are unusually high. Builders should consider using superefficient appliances, installing one grade better windows than the MEC requires, performing duct tests, and incorporating solar orientation into the plans. These features could be sold to homebuyers as ones that distinguish the house from standard MEC houses.


Making MEC Work: Lessons from Michigan
The MEC raises home buyers' first costs a little, but it lowers operating costs a lot. For example, according to DOE studies conducted at Pacific Northwest National Laboratories, complying with the MEC would increase the initial first-cost of a typical single-family home in Michigan by about $1,400, compared to complying with the older Michigan code. This increase in cost would be included in the mortgage, so that the initial increased first-cost to the home buyer would be about $300. The net savings in energy should be about $90 a year. The first few years, the MEC buyer has less money than the typical home buyer. However, in approximately four years, the MEC buyer will have more money than the typical buyer, and these savings due to reduced energy costs will continue throughout the life of the house. This means that the average new home buyer will realize a net savings in only about four years. 

The Importance of Time and Place

New compliance software makes the MEC easier to use than ever before, but the manner in which the code is adopted has room for improvement. Michigan, for example, adopted the 1993 MEC, effective July 1, 1995; however, builders convinced their legislators to repeal it in December 1995, replacing it with standards developed 20 years ago. There is a movement afoot in Ohio to follow Michigan's lead.

Builders in Michigan had several complaints against the MEC: that it is too complex and difficult to follow; that compliance would significantly increase the cost of each house; and that this added cost would make housing unaffordable for low-income home buyers. Moreover, some builders complained that they were not given enough warning of the code's adoption. Michigan began enforcing the code immediately following its adoption, delaying some builders' existing contracts as they scrambled to meet the new requirements.

Adoption and implementation of any new regulation must account for the typical construction project cycles in order to minimize the impact on homebuilders. This includes everything from initial design to material suppliers and subcontractors. Homebuilders must account for project costs when they first approach lenders for project financing. To require that they meet an ever changing set of project requirements, including building codes, can significantly impact their profits. While cost increases in lumber prices, local taxes, and market conditions are not always foreseeable, code changes should be.

Adopting a code should include planning for its implementation. This includes increasing builder community awareness, making code compliance materials available, and planning a training program for builders and code officials. Only after proper planning and training should the code become mandatory. While the MEC is not perfect, these steps can reduce its impact on homebuilders.

Improving the code by providing more options to meet compliance could also help builders. For instance, the MEC's provisions are oriented towards houses in heating climates. In cooling climates, design elements such as shading and overhangs, and measures such as radiant barriers, are often more efficient and cost-effective than the thermal-envelope provisions emphasized in the code. Still, the MEC is an improvement over many existing codes. 

It is possible for builders and energy code advocates to work together, as in the states of Alabama, California, Vermont, Delaware, and New Mexico. Most of these states are using or considering MEC. Builders in these states have supported energy codes as a way to assure homebuyers a quality home.


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