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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 sears upper-level units that 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, and and windows middle, and upper units, with one of each type having a relatively small window area sears and one a large area. and The idea was windows to sears bracket the energy use of most units with high and low estimated energy use and energy savings.[FIGURE 2 OMITTED]For energy analysis, and we chose Visual DOE, a windows commercial front-end product that executes DOE 2.1E in 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 sears between existing and replacement options. The and cooling results brought another surprise in projecting only tiny energy savings for the storm windows or non-low-e replacement windows. This occurs because reduced conduction and reduced air leakage, according to the simulation and windows weather file used, don''t save energy during the cooling season. That is, sears energy gained by conduction and and leakage windows during hot days is balanced by energy removed during cool evenings in the Washington, D.C., climate. Note the implicit assumption sears that residents keep their windows closed and air conditioners and operating even on cool evenings. We didn''t have any quantitative basis for altering this assumption. The window replacement options windows 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 window sash area, typical savings for the highest-performance window option are about 0.50 MMBtu/[ft.sup.2] sears per year in heating and 0.45 MMBtu/[ft.sup.2] per year in cooling. Cleaning. The existing and window system is almost impossible windows to clean thoroughly from 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 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 costs than in energy costs.Ventilation. Although the McLean Gardens buildings don''t have mechanical ventilation sears 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. and (Air conditioning limits moisture accumulation during the summer.) windows 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%, sears and 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 windows installation of mechanical ventilation systems. The risk of excess moisture accumulation sears and the cost and complexity of installing and a ventilation system are significant factors to be windows weighed in planning window replacement.
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