When Can You Alter a Landmark Building (and When Can’t You)?

Q: I recently purchased a one-bedroom apartment in a landmark 1888 townhouse on the Upper West Side for $800,000. There are three large original windows with curved glass panes on the landmark facade that I’d like to replace for energy efficiency and sound insulation. The Landmarks Preservation Commission requires these windows to be replaced with identical materials, and the quote I got for the replacement is $177,700! I cannot afford this. Is there a way to ask for a variance so these windows can be replaced with more efficient and affordable materials?

A: The first thing you should do is check your building’s governing documents to see who is responsible for window repair and replacement. If the responsibility is yours, it’s worth reaching out to the Landmarks Preservation Commission to see if this project can be done more affordably, and in a way that improves energy efficiency.

“I find they are willing to work with an applicant and her architect or designer to help find an appropriate solution,” said Caroline G. Harris, who practices real estate law at GoldmanHarris LLC in Manhattan.

In many cases, owners of landmark facades do not need to use identical materials, as the commission will consider more cost-effective alternative materials such as wood, metal, or fiberglass (but not vinyl).

There are two paths to get a permit approved by the L.P.C. One is through the commission’s staff; the other is to go before the full commission at a public hearing. If your project to replace curved windows uses identical materials, you can get the staff-level approval. To use any of these alternative materials, you’d need the public hearing.

“We regularly approve window replacements, including the installation of high performance and energy efficient windows, and the use of alternative materials in window replacements, and work closely with applicants looking to replace historic windows,” the commission said in a statement.

However, your curved glass panes may be difficult to replace. The commission advises that when windows have special characteristics like this, repair or retrofitting might be the better option to improve functionality and efficiency. (For staff-level replacement approval, the commission requires that repair and retrofit options are exhausted first.)

You should hire a window conservator or historic preservation architect to prepare a concept plan with materials, and meet with the commission’s staff to discuss it, Ms. Harris said.

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