DNR Construction is the leading weatherization contractor in the Midwest. Being a weatherization contractor, allows us to have a large degree of knowledge on how replacement windows affect the homes thermal envelope. Typically replacement windows are the last improved element in weatherizing your home. Windows and doors may contribute to 15-20% of a homes heat loss but because of their cost and energy payback, they should be looked at last. Only after air sealing and insulation, and upgrading heating and cooling systems, should windows be replaced. In our energy assessments of a home, we look at the past payback first. Windows are replaced for functionality and aesthetics first, with the increased benefit of energy efficiency.

Replacing windows to maximize and increase energy efficiency

First the window must be measured correctly. Each window is originally installed with certain elements, which must be known prior to establishing the replacement window size. For example, is the exterior brick or siding? How much of the existing window will need to be removed? How will the window sit on the interior? Exterior? If these questions are not asked before establishing the window size there may be no benefit to replacing the windows.

Second, the gaps within the window frame must be insulated with materials, which stop air infiltration. These products are typically rigid in nature such as low expansion foam and caulk. Windows, which are surrounded by lead weight cavities, which are common in Chicago, must be dense-packed with cellulose insulation. The dense packed cavity will stop air infiltration and add R-value to the cavity. Many times when an infrared scan is performed, homeowners will have a high performance glass in the window with a cold empty lead weight cavity sitting right beside it. This cold cavity will cause drafts and temperature differential in the room where they reside. Contractors will often “stuff” fiberglass insulation between the window and frames and inside the lead weight cavity. Realize that as you compact fiberglass insulation the R-value is drastically reduced and fiberglass does not stop air flow.

Third, after completing a full window replacement of the home, a blower door test (see more on this test under weatherization) should be used to see the reduction in air infiltration as well as making sure each window is “airtight”. If this not completed, the homeowner and contractor are unable to know the direct benefits of the window replacement.

There are many types of window designs and manufacturers. DNR Construction does not manufacture it own windows but partners itself with companies who have a strong track record of quality and service. Common materials used in the construction of windows are vinyl, fiberglass, and wood. Wood windows typically have aluminum or vinyl exterior clad which comes in a variety of colors and increase the lifespan of the window.

DNR Construction has an honest approach educating its customers on the various products and their costs. We price jobs to win them and are consistent with our pricing across the board. This means we do not sell by using hard closing techniques and keep our pricing the same rather than trying to take make a higher profit on a certain job. In fact are sales people are the owners and typically only two representatives of DNR Construction will provide every estimate.

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