Storm Windows and Doors for Historic Homes
There is a quiet myth in the window business that the only way to make an old window efficient is to tear it out. It is not true, and the research backs that up. A historic wood window paired with a good storm window performs about as well as a modern replacement, at a fraction of the cost, and without throwing away a window that has already lasted a hundred years and could last another hundred.
That is the whole idea behind a storm window. It adds a second layer that traps a pocket of still air and cuts the drafts, which is where most of the heat actually escapes in an old house. The original window stays right where it is, doing its job, protected from the weather. You get the comfort and the efficiency without losing the wavy glass, the true divided lights, and the old-growth wood that make the window worth keeping in the first place.
Heritage Restoration builds and fits storm windows and storm doors for historic homes across Rhode Island, including custom units for the odd-sized and out-of-square openings that old houses are full of.
What a Storm Window Actually Does
The Department of Energy puts the savings from low-e storm windows at 10 to 30 percent on heating and cooling, depending on the windows you start with. The EPA estimates that storm windows certified by Energy Star save a homeowner around 350 dollars a year over single-pane glass, and pay for themselves in about three years. In a cold New England winter, over a single-pane historic window, that is a real and noticeable difference.
The reason they work so well comes down to air. In an old house, the biggest source of heat loss around a window is not the glass; it is the air leaking through the gaps. A well-fitted storm window slows that air movement down dramatically, which is why a room with storms feels warmer and less drafty almost immediately. It also raises the temperature of the inside glass surface, so you stop feeling that cold radiating off the window on a January night.
Interior or Exterior
There are two ways to add a storm window, and the right choice depends on the building and the situation.
Exterior storm windows are the traditional approach and the most common. They mount on the outside of the window, which protects the original sash from rain, sun, and weather, and they sit outside the thermal barrier, so condensation is rarely an issue. They are visible from the street, which matters in a historic district, so the profile and color have to be chosen carefully.
Interior storm windows, sometimes called inserts, fit on the inside of the window. They are nearly invisible from outside, which makes them a good answer where a historic district does not allow exterior changes, and they often seal tighter against air leaks. They do not protect the outside of the original window, and they need to be fitted well to avoid trapping moisture against the original sash.
In either case, the right move is to weatherstrip and tune up the original window first, then add the storm over a window that is already working as it should.
Storm Doors
Storm doors are a different calculation. Honestly, they save far less energy than storm windows, and the National Park Service says as much, since a solid historic door is already a decent insulator on its own.
The real reason to add a storm door is to protect a historic entry door from weather and sun, and to let you open up for light and ventilation without leaving the main door exposed. When a storm door is the right call, we build wood units with traditional joinery and interchangeable glass and screen panels, designed to show off the original door rather than hide it behind a sheet of aluminum.
Custom Work for Old Openings
Old houses rarely have standard windows. Openings are arched, circular, Gothic, or simply out of square after a couple of centuries of settling, and an off-the-shelf storm window will not fit any of them.
We build custom storm windows to match whatever the opening actually is, using rot-resistant wood, traditional joinery, and low-e glass where it makes sense, painted to match the window. The result protects the original, performs the way it should, and looks like it belongs on the building.
Common Questions About Storm Windows and Doors
Are storm windows worth it?
For an old house with single-pane windows, yes, especially in a climate like ours. The Department of Energy puts the savings from low-e storm windows at 10 to 30 percent on heating and cooling, and the EPA estimates a yearly savings of around 350 dollars over single-pane glass, with the storm paying for itself in roughly three years. Beyond the dollars, the comfort difference is immediate, because the storm cuts the drafts that make an old room feel cold. The one condition is that storms work best over a window that is in sound, repairable shape, which is why we usually tune up the original window first.
Are storm windows as good as replacement windows?
They are much closer than the replacement-window salesman will tell you. A 2002 study by Lawrence Berkeley National Laboratory found that a historic window paired with a low-e storm window performed very similarly to a modern low-e replacement window. The National Park Service reached the same conclusion, noting that the small amount of air infiltration left over is a matter of comfort rather than energy. So you can get replacement-level performance for roughly a third to a half of the cost, while keeping a window that can be repaired part by part and last another century, instead of a sealed replacement unit that has to be thrown out entirely in about twenty years when one component fails.
What is the difference between interior and exterior storm windows?
Exterior storms mount on the outside and are the traditional choice. They protect the original window from the weather and rarely cause condensation problems, but they are visible from the street, so they matter in a historic district. Interior storms, or inserts, fit on the inside, are nearly invisible from outside, and often seal a little tighter, which makes them a good option where exterior changes are not allowed. The tradeoff is that they do not protect the exterior of the original window and need a tight fit to avoid trapping moisture. Which one is right comes down to your historic district rules, whether the window needs to open, and how the building looks.
Can you put storm windows over old single-pane windows?
Yes, that is exactly what they are made for. Storm windows are designed to go over an existing window, not replace it, and adding one over a single-pane historic window is one of the best things you can do for it. The storm improves the energy performance and shields the original sash from the weather, which can stretch the exterior paint cycle on the window from a few years to twenty or more. The one detail that matters is ventilation. An exterior storm needs small weep holes at the bottom so any condensation can drain, and the original wood stays dry.
Are storm windows allowed in a historic district?
Usually, yes, and that is one of their advantages. Because storm windows are reversible and protect rather than replace the original window, they are generally approvable in Rhode Island's local historic districts, where vinyl replacement windows usually are not. Exterior work visible from the street still requires a Certificate of Appropriateness before a building permit, and districts often want a narrow profile with the frame color matched to the window and the storm's meeting rail lined up with the window's. We build storms with those details in mind so they pass review and look right on the building. Where a district will not allow any exterior change at all, interior storms are the answer.
