Equipment sizing. The higher-performance window replacement options would allow reduced sizing of the residential unit heat pumps, as the heat pumps are eventually replaced. choosing The replacement highest-performance replacement option is estimated to reduce peak heating loads 33%-47%, and peak cooling loads 19%-33%. This would allow a replacement heat pump sized at least one step smaller than the existing pump in pretty much every residential unit, yielding reduced replacement cost, reduced peak loads on the utility, reduced windows operational noise level, and possibly better dehumidification 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 choosing clear glass options replacement produce only small peak cooling load reductions and peak heating and peak cooling windows are roughly 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.

Cleaning. 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, once or twice a year. Tilt-in replacement windows, and elimination choosing 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 replacement have mechanical ventilation systems, reports windows of excess moisture accumulation and mold growth are uncommon. The leaky windows are undoubtedly a major factor in providing choosing 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 replacement cause paint failure and mold growth in some units. This issue could be addressed windows directly through the installation of mechanical ventilation systems. The risk of excess moisture accumulation and the cost and complexity of installing choosing a ventilation system replacement are significant factors to be weighed in planning window replacement.

It''s clear that energy windows savings alone won''t justify window replacement (see choosing "Other Considerations in Window Replacement"). replacement If windows are to be replaced in any case, however, windows the 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 choosing 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 replacement and other effects may be difficult to quantify in dollar windows 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 of many things to consider in deciding whether and when to undertake a major window replacement project. Several other important factors are discussed below.