01142nas a2200121 4500008004100000050001500041245009000056210006900146520068100215100002100896700002500917856007800942 2006 eng d aLBNL-6014600aWindow-Related Energy Consumption in the US Residential and Commercial Building Stock0 aWindowRelated Energy Consumption in the US Residential and Comme3 a

We present a simple spreadsheet-based tool for estimating window-related energy consumption in the United States. Using available data on the properties of the installed US window stock, we estimate that windows are responsible for 2.15 quadrillion Btu (Quads) of heating energy consumption and 1.48 Quads of cooling energy consumption annually. We develop estimates of average U-factor and SHGC for current window sales. We estimate that a complete replacement of the installed window stock with these products would result in energy savings of approximately 1.2 quads. We demonstrate that future window technologies offer energy savings potentials of up to 3.9 Quads.

1 aApte, Joshua, S.1 aArasteh, Dariush, K. uhttps://facades.lbl.gov/publications/window-related-energy-consumption-us02349nas a2200157 4500008004100000050001500041245002400056210002400080260003100104520190300135100002502038700002702063700002102090700001902111856006102130 2006 eng d aLBNL-6004900aZero Energy Windows0 aZero Energy Windows aPacific Grove, CAc08/20063 a

Windows in the U.S. consume 30 percent of building heating and cooling energy, representing an annual impact of 4.1 quadrillion BTU (quads) of primary energy. Windows have an even larger impact on peak energy demand and on occupant comfort. An additional 1 quad of lighting energy could be saved if buildings employed effective daylighting strategies.

The ENERGY STAR(r) program has made standard windows significantly more efficient. However, even if all windows in the stock were replaced with today's efficient products, window energy consumption would still be approximately 2 quads. However, windows can be "net energy gainers" or "zero-energy" products. Highly insulating products in heating applications can admit more useful solar gain than the conductive energy lost through them. Dynamic glazings can modulate solar gains to minimize cooling energy needs and, in commercial buildings, allow daylighting to offset lighting requirements. The needed solutions vary with building type and climate. Developing this next generation of zero-energy windows will provide products for both existing buildings undergoing window replacements and products which are expected to be contributors to zero-energy buildings.

This paper defines the requirements for zero-energy windows. The technical potentials in terms of national energy savings and the research and development (R&D) status of the following technologies are presented:

Market transformation policies to promote these technologies as they emerge into the marketplace are then described.

1 aArasteh, Dariush, K.1 aSelkowitz, Stephen, E.1 aApte, Joshua, S.1 aLaFrance, Marc uhttps://facades.lbl.gov/publications/zero-energy-windows01767nas a2200169 4500008004100000050001500041245005000056210004900106260002900155300001200184490001400196520124500210100002101455700002501476700001901501856007701520 2002 eng d aLBNL-5191300aFuture Advanced Windows for Zero-Energy Homes0 aFuture Advanced Windows for ZeroEnergy Homes aKansas City, MOc06/2003 a871-8880 v109, pt 23 a

Over the past 15 years, low-emissivity and other technological improvements have significantly improved the energy efficiency of windows sold in the United States. However, as interest increases in the concept of zero-energy homes—buildings that do not consume any nonrenewable or net energy from the utility grid—even today's highest-performance window products will not be sufficient. This simulation study compares today's typical residential windows, today's most efficient residential windows, and several options for advanced window technologies, including products with improved fixed or static properties and products with dynamic solar heat gain properties. Nine representative window products are examined in eight representative U.S. climates. Annual energy and peak demand impacts are investigated. We conclude that a new generation of window products is necessary for zero-energy homes if windows are not to be an energy drain on these homes. Windows with dynamic solar heat gain properties are found to offer significant potential in reducing energy use and peak demands in northern and central climates, while windows with very low (static) solar heat gain properties offer the most potential in southern climates.

1 aApte, Joshua, S.1 aArasteh, Dariush, K.1 aHuang, Yu, Joe uhttps://facades.lbl.gov/publications/future-advanced-windows-zero-energy