An Energy Sketch

"During the early stages of design, precision is not the goal," says Brown. "The idea is to allow designers to consider energy at the same time as basic architectural issues, such as site orientation, elevation composition and functional relationships between spaces."

Instead of calculating a precise heating and cooling load, the software helps the designer make fundamental decisions. How should the building be oriented? Where should windows be located and how big should they be? How does the overall form of the building affect energy use? What materials should be incorporated?

This program is not for engineers, mechanical contractors or energy techies. If you want annual energy use, equipment sizing or economics, you'll have to look elsewhere.

Drawing Mode

You can use the program's simple drawing tools or electronically paste drawings from other programs. With a flatbed scanner, you can scan those napkin sketches for pasting into Energy Scheming. To set the proper scale, the program prompts you to draw a line of known length. So if you know the wall is eight feet tall, you can trace over that line to set the scale.

Figure 1. Takeoff Screen

Graphical Data Entry

The most distinguishing feature of the program is its dedication to graphic manipulation. You can operate virtually every function with the mouse. You could complete an entire building study without touching the keyboard, although numerical inputs are also possible.

"Architects are visually-oriented," says Brown. "Energy Scheming is intended to plug into the design process in a way that makes designers comfortable."
To takeoff dimensions for walls, floors and other elements, you click-and-drag over an area of the base drawing with the Tape Measure Tool. (Figure 1) You can pick predefined building elements, such as a "6-inch wall," or build your own from a menu of components (siding, sheathing, insulated wood framed wall, drywall). If the generous supply of options isn't enough, you can dig through a few dialog boxes to enter a numerical value.

Several features remove the drudgery from energy calculations. For example, you can takeoff roof area from either a plan or elevation view. You then select a roof slope--graphically--and the program calculates the actual roof area. Window area is automatically subtracted from wall area. Descriptions of building elements can be changed at any time, allowing you to experiment with many options.

Window Sizer

The Rule-of-Thumb menu allows you to quickly determine the size of windows for optimum solar heating, natural ventilation and daylighting. This feature alone is worth having the program. You can quickly change window area and see the impact of that change immediately.
Daylighting can be a complicated design problem. Energy Scheming allows you to create up to five daylighting zones in the building. Windows and skylights are assigned to these zones.

Results

Energy use is calculated on four representative days of the year. The calculations take only a few minutes, if you use the acceleration feature. However, it prevents you from doing other tasks with the computer. If you continue to work, the calculations will take longer.

The easiest way to view the results is the Graphic Report (Figure 2), which shows heat gain and heat loss by hour for each of the calculation days. The graphic report can be presented as net heat flow, total gain and loss, or gain and loss by element (walls, floors, etc.) Heat gains appear as bars above the zero axis, while losses appear below. Your goal is to shorten the bars, so they get as close to the zero axis as possible. For a detailed view of a single hour, you just click on a bar in the graph.

The graphic report shows helps you identify the best opportunities for energy saving design changes. The value of the program shows when you modify the building and then look at the graphic report to see how your changes affect the loads.

Figure 2. Performance Report

Numeric reports--in overwhelming detail--also are available. Virtually every input and output is presented. To print all the reports for a sample building required over 70 pages. Fortunately, you can print only selected reports, such as the annual summary or the building data.

Learning Curve

Heat flow in buildings is a complex process. Energy Scheming tries to address all the factors. As a result, the program can seem quite complex. It offers many options for defining building materials and characteristics. You can then identify "Energy Strategies" that range from operable window shades to ventilation. Luckily, the program makes assumptions about most of these variables for you. That allows you to get started quickly, and tinker with the details later.

Expect to spend 8 to 10 hours learning how the program works. After the initial learning curve, producing an energy study of a house can take only a couple of hours. Anyone who has mastered a computer aided drafting (CAD) program should have no problem with Energy Scheming.

Improvements

Energy Scheming does an reasonable job of handling the complexities of building heat load, without intending to be a building simulation. Several improvements could help designers more easily use the program's power. Takeoff icons often clutter the screen. Users should have the option of using menus to create and manage takeoffs. Calculations need speeding up. While the goal is always to reduce building load "as much as possible," users need a benchmark for comparison. This could be a "bottom line" number or a target that shows on the graphic report.

Brown and his colleagues are working on several projects that should be released in the future. Version 3.0 of Energy Scheming will add features that help to interpret the results with suggestions for improving performance. They are developing a new program based on Energy Scheming specifically for structural insulated panels. They have developed a module for Softdesk that will allow AutoCAD users to assess the energy use of their designs.
All these efforts make it more likely that architects and designers will address energy performance at the early stages of design instead of the end.