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It''s clear that replacement energy savings alone windows won''t justify window replacement (see "Other Considerations in Window Replacement"). If windows are to be replaced in any case, however, the analysis provides justification for an upgrade to high-performance glass. installation At a cost replacement 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 condition estimated the current value of deferred maintenance at over $1 million, windows which reduces the comparative installation cost of window replacement. Comfort and other effects may be difficult to quantify in dollar terms, but they have replacement important costs and benefits. Energy saving is just one factor to be weighed in this complex and expensive decision.Energy windows savings resulting directly from window replacement is just one of many things to consider in deciding whether and when to undertake installation a major window replacement project. Several other replacement important factors windows are discussed below. There are three basic configurations of residential units at McLean Gardens: bi-level units on the first two floors, middle-level units, and upper-level units installation that include loft space under the slope of the roof (see Figure 2). For our energy simulations, we selected six actual replacement floor plans, two each of lower, middle, windows and upper units, with one of each type having a relatively small window area and one a large area. The idea was to bracket the energy use of most units with high and low estimated energy use and energy savings.[FIGURE 2 OMITTED]For energy analysis, we chose Visual DOE, a commercial front-end product that executes DOE 2.1E in performing hourly simulations of energy installation use in the building. Visual replacement DOE doesn''t perform air leakage calculations, however, which we needed to get a good windows comparison between existing and replacement options. Cleaning. The existing window system is almost impossible installation to clean thoroughly from replacement inside the building. As a result, many residents pay for professional cleaning, at a cost of $100 or more, once or twice a year. Tilt-in replacement windows, and elimination of the separate storms, would allow relatively easy cleaning windows of all surfaces from the interior. Thus, residents who drop professional cleaning in favor of doing it themselves, and consider it a free-time activity, might save more in cleaning installation costs than in energy costs.Ventilation. Although the McLean Gardens buildings don''t have mechanical replacement ventilation systems, reports of excess moisture accumulation windows and mold growth are uncommon. installation The leaky windows are undoubtedly a major factor in providing natural ventilation rates sufficient to limit moisture accumulation during cold weather. (Air conditioning limits moisture accumulation during the summer.) Window replacement would replacement significantly reduce overall building infiltration. Our project did not include measurement of overall building windows leakage, but we believe that overall natural infiltration rates would be cut by more than 50%, and that the resultant increase in interior humidity and condensation would probably installation cause paint failure and mold growth in some units. This issue could be addressed directly through the installation of mechanical ventilation systems. The risk of excess moisture accumulation and the cost and replacement complexity windows of installing a ventilation system are significant factors to be installation weighed in planning window replacement.
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