MakeHeat

How Much Will It Really Save?

“… Lets assume a 2,000 square foot (~45′x45′) house with eight foot ceilings. This house would have 5,440 square feet of ceiling, floor, and wall space, of which 120 square feet represent ten 3′x4′ windows. If your windows currently have an R-Value of 1 and the rest of the building envelope is insulated to R-13, your building’s average R-Value would be 12.73. Replacing your windows with windows rated to R-3 would increase this to 12.78, or 0.4%. Saving a couple of dollars a year on your heating bill is probably not worth spending $5,000. In fact, a study mentioned in this TreeHugger.com article says that the payback period of replacing old wooden windows is up to 400 years! …”

The blog goes on to say:

“…One undertaking that might have a more reasonable ROI is insulation. Since replacing wall insulation is a bit more involved and costly, we are typically limited to replacing floor or ceiling insulation. Attic insulation like cellulose or fiberglass can be blown in using what resembles a giant vacuum cleaner running in reverse. Some local equipment rental stores or home improvement warehouse stores even rent this equipment by the hour. Loose fill insulation typically has an insulating value greater than R-3.5 per inch. Assuming that our hypothetical house already has four inches of loose-fill insulation (~R-13) we can add another four inches to bring it up to R-26 for very little expense and a 37.5% increase over our previous average insulation value. …”

via Ask Pablo: Is Replacing Windows A Good Investment? : TreeHugger.

In our case, the replacement of the windows was imperative, since they were “murder weapons”: every time you opened one window, the other one would slide down and try to break your arms. Fortunately, we’d taken the time and money before hand and added insulation to the attic (R-48), and did our own home energy audit, finding many other areas where the heat was escaping.  The “free” home energy audit given by the state just said “you need to replace your incandescent bulbs, replace your windows and (with no real specific points) insulate.  Here’s a few free CFL’s. “.  A blower door test and a thorough inspection would have cost us about $500, but we found a better solution which is a book and several excel spreadsheets offered by David Andersen (link). Another low-cost investigation you can do yourself and save a lot of money is following my “DIY Thermal Heatmap” (link). All you need are an excel spreadsheet, an infrared thermometer and a digital camera.