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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 basement units that replacement include loft space under the slope of the roof (see Figure 2). For our energy simulations, we selected six actual floor plans, two each of lower, middle, and upper windows units, with one of each type having a relatively small window area and one a large area. basement The idea was to bracket the energy use of most units with replacement 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 use in the building. Visual DOE doesn''t perform windows air leakage calculations, however, which we needed to get a good comparison between existing basement and replacement options. It''s clear that energy savings alone won''t replacement 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. windows 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 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, but they have important costs basement and benefits. replacement Energy saving is just one factor to be weighed in this complex and windows expensive decision.Energy savings resulting directly from window basement replacement 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. Cleaning. The existing window system is almost windows impossible basement to clean thoroughly from inside the building. As a result, many residents pay for professional cleaning, replacement at a cost of $100 or more, once or twice a year. Tilt-in replacement windows, and elimination of the separate storms, would windows allow relatively easy cleaning of all surfaces from the interior. Thus, residents who drop professional cleaning in favor of doing it themselves, and consider basement it a free-time activity, might save more in cleaning costs than in energy costs.Ventilation. Although the McLean Gardens buildings replacement don''t have mechanical ventilation systems, reports of excess moisture accumulation and mold growth are uncommon. 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 significantly reduce overall building infiltration. Our project did not include measurement of overall building 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 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 complexity of installing a ventilation system are significant factors to be weighed in planning window replacement windows.
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