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To do this, we selected CONTAM, a program developed by the National Institute for Standards and Technology and available flee through its Web site (see information at the end of this article). CONTAM calculates instantaneous values of air flow through openings in buildings, using the flow characteristics of each opening, orientation, height, and other factors, based on a weather file that provides temperature and wind information. We set up our CONTAM runs to calculate air flow for replacement each hour of the typical year, wood and then summarized the results by month.To complete the energy simulation inputs, windows we gathered information replacement on building envelope construction and estimated appliance loads, hot water usage, and occupancy for each unit type. Water-to-air wood heat pumps installed in each unit provide heating and cooling at windows McLean Gardens. Six central 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. We performed a total of about 100 simulations, replacement estimating energy use for wood 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 of our assumptions as a result. We also did some basic sensitivity runs to windows evaluate the effect of replacement orientation and shading.The results brought some surprises (see Figure 3 for typical results for one apartment type). The first is the large projected heating savings for the storms-only replacement, an option with a far lower cost than full window wood replacement. This results from the combined effects of reduced infiltration and the estimated reduction in U-value attributable to a tighter system. Comfort. Window replacement at McLean Gardens would result in reduced window air leakage and increased wintertime temperatures at the windows inner glass surface. Reduced air leakage means fewer drafts near windows. Increased wintertime glass temperature would reduce cold convection currents that spill off windows, further reducing the sensation of drafts. The temperature increase would also increase the average radiant temperature of the indoor environment. (Average replacement radiant wood temperature has nearly as strong an influence on comfort as does air temperature.) While all the replacement windows options would yield some increase in temperature, the higher-performance low-e, argon-filled glass would offer the greatest increase. While improved comfort has value in itself, it may also result in thermostat adjustments that yield additional real energy savings.
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