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It''s clear that energy savings alone won''t justify window replacement (see "Other Considerations in Window Replacement"). buy If windows replacement are to be replaced in any case, however, the analysis provides justification for an upgrade to high-performance glass. At a cost of $60 per window, the payback on low-e argon filled glass is a reasonable 9 years.And there are other issues to be considered. The companion study on window windows condition estimated the current value of deferred maintenance at over $1 million, which reduces the comparative cost of window replacement. Comfort and other effects may be difficult to quantify in dollar terms, online but they have important costs and benefits. Energy saving is just one factor to be weighed in this buy complex and expensive decision.Energy savings resulting directly from window replacement is just one of many things to consider in deciding whether and when to undertake a major window replacement project. Several other important factors are discussed below. The cooling results brought another surprise replacement in projecting only tiny energy savings for the storm windows or non-low-e windows and online replacement windows. This occurs because reduced conduction and reduced air leakage, according to the simulation and weather file used, buy don''t save energy during the cooling season. That is, energy gained by conduction and leakage during hot days is balanced by energy removed during replacement cool evenings in the Washington, D.C., climate. Note the implicit assumption that residents keep their windows closed and air conditioners operating even on cool windows evenings. We didn''t have any quantitative online basis for altering this assumption. The window replacement options with low-e glass, on the other hand, show significant projected cooling savings, largely as a result of reduced solar Calculated as energy savings/[ft.sup.2] of buy window sash area, typical savings for the highest-performance window option are about 0.50 MMBtu/[ft.sup.2] per year in heating and 0.45 MMBtu/[ft.sup.2] per year in cooling. To do this, we selected CONTAM, a program replacement developed by the National Institute for windows Standards online and Technology and available flee through its Web site (see information at the end of buy this article). CONTAM replacement calculates instantaneous values of air flow through openings in buildings, using windows the flow characteristics of each opening, orientation, online height, and other factors, buy based on a weather file that provides temperature replacement and wind information. We set up our CONTAM runs to calculate air flow for each hour of the typical year, and then summarized the results by month.To complete the energy simulation windows inputs, we gathered information on building online envelope construction and estimated appliance loads, hot water buy usage, and occupancy for each unit type. Water-to-air replacement heat pumps installed in each unit provide heating windows and cooling at McLean Gardens. Six central online plants equipped with boilers and cooling towers provide conditioned water at roughly 70[degrees]F to the heat pumps as a source or sink for energy. We took advantage of Visual DOE''s ability to model this system by grouping an upper, middle, and lower unit together with a central plant for each analysis.
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