If there is one thing constant in the world it is that home heating costs will constantly go up. So with this in mind there is a variable that homeowners can adjust and this is to make our windows more efficient in preventing heat from leaving the home.
R-Value for Energy Retention
A home's ability to keep heat or air-conditioned coolness in the home, depending on the season, is rated with the r-value. This measurement calculates the ability of a wall, window or other surface to prevent energy from leaving the home. Most insulation is measured in r-values and the most likely culprits for losing heat in a modern home are the windows.
Most building codes in northern areas of the country require that homes have values of R-15 in the walls and R-45 in the attics. The larger value for the attic is that heat rises and has a tendency to layer at the ceiling of a room where it will cool very quickly with a small amount of insulation. A pane of glass, on the other hand, has an r-vale of less than one and even a double-sealed window an only come up to R-2.
Heat Loss Through Windows
One of the best ways to show the inefficiency of normal windows is to contact a service that performs energy tests on homes. Most of these companies will have an infra-red camera (IR), which is a heat detection device cooled by liquid nitrogen. The test is usually performed on a very cold day on the outside of a home where the camera is pointed to each side the house and a picture taken. What this special camera will reveal is the thermal image of the home and the heat escaping with be lit up up in colors – yellow being the hottest - whereas the surfaces that are not leaking heat will be black, blue and violet.
With walls having R-15 to R-18 insulation dark colors appear on the scan but windows show up as bright-red due to the double-pane units being barely R-2. This will also show bright spots where the wall insulation was not installed properly or has lumped over the years. However, it is the windows that show up like the inside of the house in on fire.
Leaks and Inadequate Insulating
Performing the IR test can also show how well home is insulated, even a new home. Below windows may have white to fiery-red areas where an insulation contractor forgot to finish it. Other contractors like drywall teams and electricians would not report this unfinished job because they are focused on their own projects. In addition, there may be leaks around improperly-installed window casings that will show on IR camera.
Improving the IR Scan
- Add blown-in Insulation: This for empty spots in the walls shown on the IR scan. An experienced insulator will drill holes and top up the insulation. Then the hole will be filled.
- Attic: If the roof shows anything but dark colors top up the insulation above the attic to R-45+ , or thirteen inches of fiberglass or cellulose.
- Triple-Pane, Low E, Argon-filled Windows: These new windows reflect heat back into the home while providing less conduction or convection for heat loss.
- Caulking: Old caulk and seasoned-wood shrink over time. This exposes small gaps that promote drafts. Statistics show that the average older home has enough leaks that, if all put together, would equal the radius of a basketball.
- Plastic Sheathing on the Windows: Placing plastic on the inside window frames will raise the r-value of a window to over R-7 because plastic is a perfect thermal break. When tightened with the heat from a hair dryer it is almost transparent.
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