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There are three basic replace and house configurations of residential units at McLean Gardens: bi-level units on the first two floors, middle-level units, and upper-level units that include loft space under the slope of the roof (see Figure 2). For our energy windows simulations, we selected six actual floor plans, two each of lower, middle, 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 replace 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 house performing hourly simulations of energy use in the building. Visual DOE doesn''t perform air leakage calculations, however, which we needed to get a good comparison windows between existing and replacement options. We performed a total of about 100 simulations, estimating energy use for the six test case residences modeled with the current windows and with each of five replacement options. Thirty McLean Gardens residents responded to our request for a waiver to access utility records, and we checked our simulation results for the existing-windows case against these bills, tweaking some replace of our assumptions as a result. We also did some basic sensitivity runs to evaluate the effect of orientation and shading.The results brought some surprises (see Figure 3 for typical results for one apartment house type). The first is the large projected heating savings for the storms-only replacement, an option with a far lower cost than full windows window replacement. replace This results from the combined effects of reduced infiltration house and the estimated reduction in U-value windows attributable to a tighter system. Cleaning. replace The existing window system is almost impossible to clean thoroughly from inside the building. As a result, many residents pay for professional cleaning, at a cost of $100 or more, house once or twice a windows year. Tilt-in replacement replace windows, and elimination of the separate storms, would allow relatively easy cleaning of all surfaces from the interior. Thus, residents who drop professional cleaning in favor of doing it themselves, and consider it a free-time house activity, might save more windows in cleaning costs than in energy costs.Ventilation. Although the McLean Gardens buildings don''t replace have mechanical ventilation systems, reports of excess moisture accumulation and mold growth are uncommon. house The leaky windows windows are undoubtedly replace a major factor in providing natural ventilation rates sufficient to limit moisture accumulation during cold weather. (Air conditioning limits moisture house and windows accumulation during the summer.) Window replacement would significantly reduce overall building infiltration. Our project did not include measurement of overall building leakage, replace 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 house would probably cause paint failure and mold growth in some units. This issue could be addressed directly through the installation windows of mechanical ventilation systems. The risk of excess replace moisture accumulation house and the cost and complexity of installing a ventilation system are significant factors to be weighed in planning window windows replacement.
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