Though not intended for calculating actual energy costs, the Efficient Windows Collaborative’s window selection tool is useful for comparing different glass configurations and frame materials for windows in both cooling and heating climates.
Though not intended for calculating actual energy costs, the Efficient Windows Collaborative’s window selection tool is useful for comparing different glass configurations and frame materials for windows in both cooling and heating climates.

With window sales in a multiyear downward spiral, manufacturers have understandably embraced the tax-credit component for energy-efficient building products contained in the stimulus package. Companies like Andersen and Simonton are vocal supporters of new proposals like Home Star (sometimes called “Cash for Caulkers”; see JLC Report, 01/10). Besides being good for the industry’s bottom line, the argument goes, such programs also have the potential to save vast amounts of energy and money.

But how much do replacement windows actually save? According to consultant Marc Rosenbaum — whose New Hampshire–based company, Energysmiths, specializes in energy-efficient houses — the numbers are less compelling than some might have you believe. In a 6,000 heating-degree day climate, he says, replacing a standard clear insulated-glass R-2 (...

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