We like the technology of fiberglass door and window frames for Brooklyn brownstones. It is less toxic than vinyl, more insulating than wood, and longer lasting than any of them. Or at least as long lasting as any of them.

Fiberglass frames are also better than aluminum frames. Aluminum is one of the best heat conductors around and it makes absolutely no sense to use window or door aluminum frames in Brooklyn. You are throwing money away through heat loss via the frames. Some manufacturers counter this by insulating between the frame but any good frame should be insulated anyway so that is a moot point.

You can choose to paint fiberglass frames or not. If you don’t paint them they have virtually no maintenance.

Another thing that makes them last longer is that fiberglass is a derivative of glass. This means that the glass in the window and the glass in the frame expand and contract the same amounts (i.e. almost not at all). This reduces cracks between the glass and frame to pretty much nothing.

The two distributors that I know of who supply the NY area are two companies out of Canada. One is Fibertech and the other is Inline Fiberglass. I have bought from both.

Here is an Inline Fiberglass triple glazed sliding glass door we installed. It feels very solid and has great glazing.


Although they are pricy, fiberglass window frames definitely add value and savings. Whenever price permits we strongly recommend triple glazing for Brooklyn brownstones. It takes the R value from around 2-3 to 5-6, basically doubling the insulation value over double glazed windows.