What You Should Know About Restoring and Weatherizing Historic Windows

It’s both a blessing and a curse to live in an historic home. On the one hand, you are living in an architecturally and historically significant building, in which the walls and fittings can tell stories of many decades of past inhabitants. On the other hand, everything is very old, and in need of maintenance and restoration. It may be best to call the professionals to do the job, but here are a few things you should know if you intend to do the job yourself.

The good news about restoring and weatherizing your drafty old windows is that it isn’t really a difficult job to do in most cases. It takes a bit of skill and practice, but with time and determination, you can certainly do it yourself.

Fixing drafts

Assuming that your windows are in good condition, but they are a bit drafty, you can start the task of finding and plugging gaps. Don’t do this if you intend to remove your windows for repairs and restoration soon, otherwise you may need to do it again later.

The easiest way to test for air leaks is to use a stick of incense. Place it below the window, and step away from it, then see if the smoke is interrupted by air from outside. If it is, you need to inspect the windows. Fixing it may be as simple as recaulking the inside and outside of your window frames. The window glazing may also need replacement.

Restoring historic windows

It is commonly believed that replacing old windows can save up to 50% of energy costs. This is difficult to measure accurately, but it’s a figure that is a bit exaggerated. The windows in historic buildings are often some of its most characteristic features, especially in the case of steel frame windows in old industrial buildings. When these buildings are converted for residential use, the old windows are often replaced instead of restored. But if they have existed for the better part of a century, there is surely a better chance of repairing them than with modern windows.

Weatherizing and improving energy efficiency

If energy efficiency is the only reason for replacing old windows, you are better off keeping them and finding ways of making them more energy efficient. Similar to wooden frame windows, caulking is a big part of weatherization. Weatherstripping is the next step. There are several types available, depending on the condition of the windows, including spring-metal, vinyl strips, foam tape, and sealant beads.

Thermal glazing can be installed on top of the existing window glass to increase thermal insulation. The cheapest method is to install a sheet of rigid acrylic or glass over window sashes.

Another method is the manufacture and installation of storm windows. These windows open independently, and are installed over the existing windows to create extra thermal installation without altering the existing windows.

The best option, if the window frames and hinges can take the weight, is to replace existing single glazed glass with double glazing. This will ensure that the window’s appearance is preserved, while enhancing thermal efficiency.