There are many situations where a homeowner wants to improve the performance or the appearance of their home, but decides not to replace their existing windows with state of the art, high performance replacement windows. This may be for aesthetic reasons; they love the look of their existing windows, the color, the moldings and trims, etc. It may be that they are concerned about the new lead paint requirements and don’t want to put up with that aggravation. Or it may be because the cost of new high performance replacement windows is just out of reach right now.

Regardless of the reason, high performance storm windows offer a viable alternative to full window replacement. A high performance storm window is mounted to the exterior of your existing prime window, all the work is on the outside of your home. It can even incorporate a hard surfaced low emissivity coating on the glass to improve both the energy efficiency (U Factor) and the Solar Heat Gain Coefficient (SHGC). No, they will not do as much for energy savings as a top quality high performance glass replacement window, but they will significantly improve the performance of existing prime windows that do not currently have a high performance glass option. They also give a new, clean look to the exterior of your home and make your home more comfortable to live in.

So if for whatever reason you’ve decided not to upgrade your home at this time by replacing the existing prime windows with state of the art new windows, consider adding Low E storm windows to at least your most energy-wasting windows. See the chart below for estimated levels of improvement depending on the type of prime window you currently have.

Percentage Improvement in U Factors and Solar Heat Gain Coefficients by Adding a Hard Coat Low E storm window to an existing prime window*:

1. Wood Prime Window with single glass: U Factor — 20%, SHGC — 12%

2. Wood Prime Window with double-pane glass: U Factor — 16%, SHGC — 12%

3. Wood Prime Window with double-pane glass w/Low E: U Factor — 15%, SHGC — 7%

4. Aluminum Prime Window with single glass: U Factor — 12%, SHGC — 12%

5. Aluminum Prime Window with double-pane glass: U Factor — 9%, SHGC — 12%

6. Aluminum Prime Window with double-pane glass w/Low E : U Factor — 8%, SHGC — 7%

7. Vinyl Prime Window with single glass: U Factor — 21%, SHGC — 12%

8. Vinyl Prime Window with double-pane glass: U Factor — 16%, SHGC — 12%

9. Vinyl Prime Window with double-pane glass w/Low E : U Factor — 15%, SHGC — 7% * Storm window analysis based on Industry Test Laboratory Computer Simulation.