Friday, July 21, 2006
Options for Replacement. Replacing windows in your home
By Ann Robinson and Annie Vernon
Can you stand one more week on windows? If you've followed the past couple of columns, we did a two-part series about window styles and material choices. But we decided to give you a bonus third week, because once you've considered the style and material for replacement windows, you need to know your options for actually replacing your windows.
There are three basic methods for replacing existing windows. The first is replacement of the sash only — the framework in which the glass panes are set. Everything else — the window frames, the window sills, etc. — will remain the same, and the new window will be the same style and size as the original window. This method could be a good choice if you want to keep the same size and style, if the existing frame and sill are in good condition, both inside and out, and if there is no water leakage.
This is the least expensive method for upgrading your windows. Many manufacturers have window sash replacement kits designed for their older frames. Problems arise with this method if the original windows are not square or if the sill is crowned as opposed to flat.
The second method is replacing the interior of the existing window by installing a new sash and frame within the existing window frame. The window trim (inside and out), interior wall materials, and exterior wall materials remain undisturbed. A complete window unit is slipped into the existing window jambs against the existing stops (or trim material which "stops" the window from being able to be pushed completely through the opening). Low-expanding foam is used to seal the perimeter gaps to ensure an airtight installation.
This method provides greater energy efficiency than just replacing the window sash because the sash and frame are manufactured and tested as a unit. However, the drawback to this method is that adding a new window inside the original frame reduces the actual glass area.
The third window replacement method is to completely remove and replace the existing window — frame, trim and all. This method is required if there has been any leaking around the existing window. The new window is integrated into the wall with new head and sill flashing, flexible flashing membranes, and high-quality sealants. ("Flashing" refers to materials that help to waterproof and weather proof the window.)
With any window replacement you can change the style of the window, but with this type of window replacement, you can also change the size if desired. This is the most energy efficient form of window replacement because the window is fully integrated into the wall system. This is also the most invasive and expensive method.
Here's a final tip: Because it is hard to tell how efficient a window is just by looking at it, the National Fenestration Rating Council provides third-party performance ratings for windows and doors. The information is quite technical, but the basic rule of thumb is that the lower the numbers, the better.
You can do homework online for more information. We recommend www.nfrc.org, www.efficientwindows.org, and http://windows.lbl.gov. As always, we welcome your home architect design questions at firstname.lastname@example.org.