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It''s clear that energy savings Replacement alone won''t justify window replacement (see "Other Considerations in Window Replacement"). If windows are to be replaced in any case, however, the windows analysis provides justification for an upgrade to high-performance glass. 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 for at over house $1 million, which reduces the comparative cost of Replacement window replacement. Comfort and other effects may be difficult to quantify in dollar terms, but they have important costs and benefits. Energy saving is just one factor to be weighed in this complex and expensive decision.Energy savings resulting directly from window replacement is just one windows of many things to consider for in deciding whether and when to undertake a major window replacement project. Several other important factors are discussed house below. Equipment sizing. Replacement The higher-performance window replacement windows options would allow reduced sizing of the residential for unit heat pumps, as house the heat pumps are eventually replaced. The highest-performance replacement Replacement option is estimated windows to reduce peak heating loads 33%-47%, and peak cooling loads 19%-33%. for This would allow a replacement heat pump sized at least one step smaller house than the existing pump in pretty much every residential unit, yielding reduced replacement cost, reduced peak loads on the utility, reduced operational noise level, and possibly better dehumidification Replacement performance during the cooling season.There would be little or no equipment sizing benefit associated with the clear glass window replacement options, however. This is because the clear glass options produce only small windows peak cooling load reductions and peak heating and peak cooling are roughly for equal in these buildings. In a colder climate, where heating loads are dominant, the clear glass options would also allow equipment size reduction in many cases. There are three basic configurations of residential units at McLean Gardens: bi-level units on the first two floors, middle-level house units, and upper-level units that include loft space under the slope of the roof (see Figure 2). For Replacement our energy simulations, we selected six actual floor plans, two each of lower, middle, and upper units, with one of each type windows having a relatively small window for area and one a large area. The house idea Replacement was to windows bracket the energy use of most units with high and low estimated energy use and energy savings.[FIGURE 2 OMITTED]For energy analysis, for 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 house DOE doesn''t perform air leakage calculations, however, which we needed to get a good comparison between existing and replacement options.
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