In places where winter temperatures often drop to 20° below zero, energy-efficiency measures can make a huge difference. Through energy-modeling software, architects Doug Zaun and Rachel Wagner designed an energy-efficient home in Duluth, Minn., that met the owners' needs for a house big enough for their family but that didn't bust their modest budget. Knowing that simple forms are economical because they produce less waste, require less labor, and use less energy, Zaun and Wagner followed a less-is-more approach to locating the spaces. In the end, they produced a house with $21,600 in added costs for various energy-efficiency upgrades, an amount that they will recoup in less than 18 years if energy prices remain the same. In addition to the main article by Zaun, Wagner adds a sidebar on the energy-modeling software they used, which provided data that gave an accurate picture of how the house would perform, the added cost for various upgrades, and a realistic estimate of annual savings.