Tips for Replacing Historic Windows

There’s a lot to know when replacing windows on a historic building. Find out about the regulations, who enforces them, and what the National Parks Service has to do with it.

October 3, 2022

Historic properties are subject to rules and regulations that can be more restrictive than typical building code requirements. And these regulations will vary from one property to another. To help navigate these historically murky waters, we spoke with Charles (Chick) McBrien, a Marvin architectural expert who has over 40 years of experience and has spent the last 20 years consulting on historic and commercial window preservation projects. Chick provided valuable insight about the guidelines for historic properties, how the process works, and more to help you avoid mistakes on your window replacement project.

Who makes the rules?

Most changes or improvements performed to a building’s exterior on properties that are listed on the United States National Register of Historic Places, will be subject to the 10 standards spelled out in The Secretary of the Interior's Standards for Rehabilitation. According to the National Parks Service (NPS), who administers the Standards, “The intent of the Standards is to assist the long-term preservation of a property's significance through the preservation of historic materials and features.”

A home or business may not be on the national register, but if it’s located in a historic district, then the property could also be subject to preservation standards, which could be administered by a state, county, or city heritage preservation review panel. These non-federal authorities often adapt, and closely follow, the NPS’s Standards for Rehabilitation. That said, Chick points out that, “Local standards can be more stringent or less stringent depending on the makeup of the review panel and the historic significance of the area.”

Before you can replace historic windows, you’ll need to appear before the review panel that administers the district where a property is located and make the case for the new windows you want to install. When you meet with the review panel, bring as much documentation and as many photos of the existing and proposed windows as you can. An experienced architect or Marvin representative will be able to help with this process.

What are the rules?

The standards that apply to properties located in historic districts are not hard and fast rules or laws. Each historic property faces unique challenges, and it would be unreasonable to hold every building to the same criteria.

“Every application is reviewed on its own merits,” Chick says. “And while preservation is the ultimate goal, restoring a building to its original condition might not be the specific objective. A 150-year-old property can acquire a new historic relevance. For example, If a house was built in 1850, but a historically significant person or family lived in the house from 1900 to 1925, then the objective of a restoration might be focused on returning the building to the condition it was in during that specific time period.”

While it’s true that some historic districts are more stringent than others, most review panels realize that if the regulations are severely restrictive, very few property owners would be willing or able to invest in the preservation of our shared heritage. This is why the NPS added this language to their Standards, “The Standards are to be applied to specific rehabilitation projects in a reasonable manner, taking into consideration economic and technical feasibility.”

Should you repair the original windows?

“The NPS places an emphasis on repairs, and so should you,” Chick says. “If the original windows can be repaired, repair them. Your historic district review panel will love you for it.” In addition to preserving a piece of history and conserving natural resources, in some cases, repairing historic windows can be less expensive. However, there are several factors to consider when choosing whether to repair or replace historic windows.

New windows will be many times more energy efficient than the existing windows. And even the efficiency of existing windows can be diminished if you decide to return them to an operating condition. Old wood windows that have been sealed shut with paint provide a better weather barrier than old operating windows, and once those seals are broken, you can expect more air infiltration, which will increase energy costs and reduce comfort levels. Old wood windows also require frequent maintenance, which can be costly. Windows exposed to extreme heat and sun, or wet climates may need touching up every couple of years.

If a building is in a smaller town, some distance away from a larger city, you may not be able to find a craftsperson with the experience and expertise to handle the job. “People who repair historic windows are more like artisans than carpenters and there’s just not as many of them out there as in years past,” Chick says. Proper training is important, not only to get the job done right but also to perform the repairs safely. Repairing old windows can expose workers and the environment to hazardous materials like lead and asbestos. If you live in a larger community, there may be an organization near you that provides a list of qualified contractors and consultants like Heritage for Ohio. And should you, or a local carpenter who’s unfamiliar with preservation work, decide to tackle the repairs on your own, there are private organizations across the country that offer online education and in-person seminars, like Minnesota-based Rethos.

Do your new windows need to be exactly the same as the originals?

When replacing historic windows, most regulatory review panels will prefer the new windows to match in size, appearance, and operation. That means retaining original window opening sizes and replicating frame thickness, sticking profiles, the widths of the styles and rails, the size and configuration of the muntin bars, color, etc. But since the Standards make a provision for “economic considerations,” these requirements don’t necessarily mean you have to sacrifice low maintenance or energy efficiency for historical accuracy.

Most glass manufacturers 125 years ago did not have the capability to create large sheets of glass. That’s why old window sashes are comprised of a collection of smaller pieces of glass separated and held in place by muntin bars. Because of the efficiency of today’s insulated glass, many review panels will allow you to install highly efficient windows fitted with simulated divided light bars that mimic the look of muntin bars. And because of the high cost of maintaining old wood windows, historic districts may possibly approve aluminum clad and fiberglass windows that last a long time with very little maintenance, even in the harshest of climates.

The most attention to detail is paid to the front or primary elevations. The regulations that apply to secondary elevations that face away from the street or are out of view from the public are often not as restrictive. This leniency means you might be able to stretch your budget by choosing less expensive windows on the back of the house, or open up a wall with larger windows to bring in more natural light and take advantage of scenic views.

Should you install inserts or full frame replacement windows?

An insert is the type of window that would be installed if the original window frame is left in place and only the existing window sashes are removed. The advantage of insert windows is that the existing trim, which may be original, elaborate, and hard to reinstall or replicate, does not have to be removed. The main disadvantage of insert windows is that it’s rarely possible to maintain the same window proportions. Insert windows have their own frame, so when the original window frame is left intact, you’re installing a frame within a frame, essentially shrinking the window opening. From the exterior, the window styles (side frames on a sash) will appear wider than the original styles. Chick says, “The daylight opening, the mass, and proportionality are considered critical architectural elements by historic review panels.” For this reason, you may be asked to install full replacement windows.

A full frame replacement is the type of window that would be installed when the original window sash, frame, and surrounding trim is removed, exposing the entire rough opening. This type of installation makes it possible to install a window that closely matches the original. It also provides the opportunity to increase the amount of insulation that surrounds the new window and allows the installation of a more resilient weather resistant flashing system. The main disadvantages of full replacement windows are that the original interior and exterior trim may be difficult if not impossible to remove and reinstall and may be unreasonably expensive to replicate. In fact, the entire process of installing full frame windows costs more than installing inserts. For these reasons, regulatory review panels might allow you to install insert windows.

How do you find out what the original windows looked like?

Don’t be surprised if you discover that the existing windows you plan on replacing are not the original windows. They might be the second or third set of windows installed in that same opening. Before you present your plan to the review panel, you need to verify what the original windows looked like. It’s unlikely that you’re going to find any plans or drawings describing the exact specifications of the original windows. But don’t fret, there are ways to track down the facts you’ll need.

Start with family photos. If a property has never left the family, dig out that old photo of Aunt Matilda—the window in the background might reveal a wealth of information. Take a look at the neighboring properties. If one of them is a similar structure, there’s a chance that the original windows on your property might have been built in the same manner. Check out the local historical society—they may have old photos or news clippings that show your property in all its original glory. And make sure to get in touch with your local historic review panel. If they don’t have the information you need, they will definitely be able to point you to additional local, state, and federal resources and might be able to instruct you on how to find and use online resources like the National Archives Catalog or your state’s Historic Preservation Office.

Why should you care?

There’s no question about it, owning property in a historic district can be challenging. Getting approvals for your plans can be time consuming. The prescribed repairs and renovations can be expensive and infusing unique personality into a historic home or business may not be an option. But there are plenty of benefits to living in a neighborhood that cares about its past enough to make the effort to preserve it. Rehabilitation of historic buildings provides high paying jobs for local artisans. Homes in neighborhoods that are protected by historic preservation regulations often have higher property values, are less susceptible to fluctuations in the real estate market, and experience a lower rate of foreclosures. Historic business districts attract boutique shops, restaurants, and other businesses that could spur economic growth and attract tourism. Also, the property may qualify for a tax credit, and there may be grants to assist with historic home or business renovation projects.

Choose the right partners

Chick highly recommends historic property owners get in touch with people that have similar concerns and interests. “Non-regulatory advocacy groups, like Main Street America, can be the most beneficial partners to owners of historic properties. These folks can not only council and give advice, but many of them have themselves started funding the purchase, renovation, and sale of historic properties.”

Every historic renovation project will encounter unique challenges that require expert solutions. Seek out your partners based on their experience. A local architect that understands historic evaluation can save valuable time researching and documenting your project and help you prepare and present your proposed renovations to the regulatory review panel. They may even have a good working relationship with some of the panel members. A seasoned and reputable contractor will be familiar with the way other similar structures in the neighborhood were built, information which could help you avoid expensive mistakes and minimize unwelcome surprises.

Marvin’s architectural project managers maintain close connections with historic field professionals, have a deep knowledge of historic buildings, and can offer invaluable assistance. If your project requires one-of-a-kind windows, Marvin experts will work with you to custom engineer them. Our highly crafted historic replacement windows will withstand the scrutiny of the most demanding review panel yet still provide exceptional performance. Who better to deliver historic window solutions than a historic window manufacturer? Marvin has been designing and building industry-leading windows for over 100 years.

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