REM/Rate Improved?

Q: I have just used my copy of the new Version 9.03 REM/Rate, the energy analysis software integrated with the Energy Star program, and I love it! Aside from the obvious improvement they made correcting the floating point error when you open it, what else is new and improved?

Debi Evans, Co-owner
Evans Heating & Cooling
Raleigh, North Carolina

Bion Howard says, "Thumbs Up":

A: I believe the long-gone floating point issue arose because certain other programs running on a user's PC conflicted with a database component in earlier REM versions. At my consulting firm, in the Washington, D.C., area, we solved this issue simply by closing certain conflicting programs, after which we rarely had problems. The issue was then fully addressed in the development of Version 9 of both REM/Rate and REM/Design.

While the underlying technical-analysis engine (engineering approach) has not been changed, there are several substantive new features and improvements in REM/Rate 9.03:

1. Version 9.03 now uses consensus-approved National Association of State Energy Officials/National RESNET Guidelines for Home Energy Ratings in place of the former metric, the HERS Council 1996 draft Guidelines for Uniformity. The NASEO HERS guidelines are currently acceptable to numerous mortgage lenders. Hence, it is advantageous to use a HERS tool that produces results in sync with them.
2. When reporting HERS results in Version 9.03, users may choose from several new output formats to produce useful graphical plots and charts. Prior versions of REM/Rate employed text tables for data and reporting.
3. REM/Rate Version 9.03 also contains compliance functionality for the 1999-2000 International Energy Conservation Code (IECC), which has been moving forward to replace the Model Energy Code (MEC).
4. A cool new feature provided on the Version 9.03 CD-ROM is a utility bill linkage to EPA Energy Star Home program's HomeCalc software. Users of REM can launch HomeCalc right from their CDs and import predicted energy costs from their REM runs, which saves time otherwise spent keying in project information. Also, REM/Rate has an electronic upload feature for directly submitting the Energy Star Homes Certificate project data back to the EPA offices in Washington, D.C., for tracking.

Users entering a basic home design can fairly accurately represent their building via the simplified input approach. However, as the complexity of a home's design increases, Architectural Energy Corporation (AEC) recommends that additional care be taken in examining values derived from the simplified input approach as they are used in the full analysis. Features such as dormers, cantilevered floors over the outside, or interior open-landscape plans between floors are envelope design issues that need to be carefully examined. Most users, however, will still be able to save time using the simplified inputting approach, but they should go back to verify that the home is being representatively modeled prior to generating final HERS rating information for their clients.

The main difference between REM and computer embodiments of the Manual J approach developed by the Air Conditioning Contractors of America (ACCA) is in the ability of each program to handle multiple zones in a residence. Also, in some code jurisdictions, one must submit a Manual J assessment prior to obtaining approval. At some point, building code officials may learn to accept other verification as well.

In most cases, the REM programs will produce single-zone (whole-building) sizing results that are acceptable for most climates in the United States.

Bion Howard is principal of Building Environmental Science & Technology (BEST), an environmental building consulting firm in the Washington, D.C. area.

Dave Roberts, senior engineer at Architectural Energy Corporation in Boulder, Colorado, contributed to this report.

For more information: For more information on REM software: Architectural Energy Corporation 2540 Frontier Ave., Suite 201 Boulder, CO 80301 Tel:(303)444-4149; Fax:(303)444-4304 Web site: www.archenergy.com For more information on the new RESNET Guidelines for Home Energy Ratings, finalized in fall 1999: Residential Energy Services Network Steve Baden, Director P.O. Box 4561 Oceanside CA 92052-4561 Tel: (760)806-3448 Web site: www.natresnet.org. Also see: Roberts, Dave. "A Comparison of the REM/Rate and REM/Design and the Manual J Design Load Calculation Procedures." May 1997 report from AEC (contact information above).

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