Old Canaan Building Materials

The original wood windows in an old New England house are almost certainly better than anything available to replace them. This is not sentiment. It is a material fact. Old-growth pine or fir sash, properly maintained, outperforms vinyl and aluminum replacement windows on every measure that matters over a fifty-year horizon. The industry that sells replacements is not wrong that old windows can be improved. It is wrong about what the improvement should be.

The wood window sash of a traditional New England house is characterized by its muntin profile — the narrow, slightly molded bar that divides the glass — and by the proportion of glass to frame. Federal-period windows have very fine muntins, sometimes as narrow as 7/8 inch face width. Victorian windows have wider, more elaborately profiled muntins. The glass in original windows is wavy and reflective in a way that modern float glass is not — the slight distortion is visible from the street and is part of what makes an old house look like an old house.

Traditional window sash in New England is built from old-growth eastern white pine or Douglas fir — dense, fine-grained, extremely stable material that painted and maintained correctly lasts centuries. The sash is double-hung in most New England residential applications: two sashes in a single frame, each sliding vertically. Glazing is single-pane in original windows, set in linseed oil putty with a triangular face profile.

A wood window sash that is properly maintained — putty reglazed every 15 to 20 years, paint renewed before bare wood is exposed, weather-stripped with appropriate compression strips at the meeting rail — is an excellent performing window. Adding a low-e interior storm window achieves energy performance comparable to a modern double-pane replacement unit at a fraction of the cost and without destroying the historic fabric.

The replacement window industry has convinced a generation of homeowners that old windows are energy problems that must be solved by replacement. The energy argument is largely false — the frame and sash of a double-hung window represent a small fraction of the building envelope's heat loss, and air infiltration at the sash, not conduction through the glass, is the actual issue. Air infiltration is solved by weather-stripping, not replacement.

Repair: find a millwork shop that can reglaze, re-putty, and repair existing sash. Replacement sash: Marvin, Pella, and several specialty millwork shops produce replacement sash in the original profiles. For historic windows requiring new sash, Architectural Components Group in Montague, Massachusetts, produces reproduction sash in period profiles.