A LAST LOOK AT HISTORIC WOOD WINDOWS
By John M. Corbett.
As seen in November/December 2001 Traditional Building Magazine.
SOME SPECIFIERS RELUCTANT TO RESTORE HISTORIC WINDOWS.
(Photo courtesy of
Paul Marlowe of Marlowe Restorations demonstrates window conservation techniques on the porch of his 1865 home in Connecticut. The occasion is a seminar for architects presented by the AIA/CT Continuing Education Commission. Such events help designers to better understand window conservation so that they can specify it more confidently.
Wood windows are perhaps the most vulnerable of historic elements,
with many millions being dumped in landfills each year. Their conservation
is a worthy goal from an historic and environmental perspective, but is
it reasonable to expect owners to subsidize these values through higher
energy and maintenance costs? That is how the multi-billion dollar
window replacement industry prefers to frame the question. For the restorer's
version of the relative costs of historic wood windows, we consulted with
Paul Marlowe, of Marlowe
Restorations, a Northford, Connecticut company specializing in wood
conservation issues. According to Paul Marlowe, new wood replacement windows
cannot equal the durability of a fully restored historic window. A melancholy
consequence of industrial development is that old growth lumber from virgin
forests has become extremely scarce. Experience has shown that second growth
lumber of even the highest commercial grade can begin to rot after just a
decade to the weather. He asserts that old growth lumber is a precious and
durable resource and that these windows are therefore an asset deserving of
The biggest problem for production windows is not rotting wood
after all, most windows are vinyl or aluminum the problem is the short
expected life of the glazing. The lifetime guarantee furnished with many
replacements is often, in effect, the lifetime of the sealed glazing units.
Current experience is that after about fifteen years the seals fail allowing
the entrance of water vapor, fog, into the cavity. Due to a number of
factors, mostly overall window quality and parts availability issues, it
will frequently be more practical to replace the entire unit rather than
the glazing only. The industry periodically claims to have solved this
problem but as the failures persist we will have to wait and see.
Welcome to the ongoing cycle of window replacement.
Restoration costs will vary considerably from window to window.
The cost of a fully restored and equipped historic window will be
four or five times that of an inexpensive replacement. This expense will
be made up over the life of the restored window by avoiding the cost of
repeated replacement. Paul Marlowe says that a complete wood window restoration will cost $1,500 per
unit for an average double hung, multiple light unit up to $4,500
for special conditions. A complete restoration includes durable epoxy
repairs, borate wood preservation strategies, installation of an array
of weatherseals, resetting of all the glazing, painting and installation
of a storm. An important factor in the retirement of wood windows has
been the assumption that they cannot be made energy efficient. The trials
that established this truism were performed under the persuasive influence
of the replacement industry using comparisons with poorly maintained
and poorly equipped existing windows. A properly fitted, glazed and
weather sealed window equipped with a high quality storm, inside or
outside, will meet modern standards for energy efficiency. A skilled
restoration specialist will make these low tech assemblies operable
and energy efficient and return to them their original life expectancy.
There are times when restoration of a given window part may not
be structurally advisable. There is some range of opinion of what is
an appropriate material for reproduction sash and parts. Caroline Sly
of Ashfield, Massachusetts is an architectural joiner who specializes
in hand tooled museum quality 18th century reproduction windows. While she agrees
that first growth material is much more durable, she finds that it is
unavailable in the eastern pine species that she requires for her work.
She asserts that she can acquire material of a suitable durability by
diligently hand selecting vertical grain heartwood from native lumber at
local sawmills. She declines to use salvage both because it is a threat
to her tools and because it is inauthentic. In contrast, Bill Hewittson
of Weston Millwork in Weston, Missouri can find the western fir and longleaf pine he uses as
first growth salvage to produce reproduction window sash. He agrees with Caroline Sly, however, that very
highly selected wood grades will outperform the norm for second growth lumber.
He also treasures his restored 19th century sash making machines but wants
to furnish a sash of historic durability for customers that specify it.
He charges a premium for milling salvage. Liz Dieter of Duluth Timber
in Duluth, Minnesota tells us that her company furnishes window makers
with the short blanks they need for their work in first growth
western species. This material is salvaged from industrial sites,
scanned for imbedded iron, custom graded and resawn. She believes that
returning this material to historic structures is its highest possible use.
Costs for faithful reproduction sash produced from either salvaged first
growth or from very highly selected second growth lumber will be
roughly equivalent to sash restoration.
Fearing to slight the multi-billion dollar window replacement industry,
we also spoke to Franz Brun of SwissShade and Security of Tucson, Arizona, who represents the German custom window maker Fauser. He gave us a short history of the German experience
with window restoration issues, noting that wartime destruction and the
extreme age of the buildings produced a dramatic surge in demand for
replacement windows. The government stepped in and set minimum standards
for both quality of replacements and for a level of period detail.
These master window makers can produce virtually any level of detail
and/or performance in a technologically advanced production setting.
Preservation trends in Europe often foreshadow those here so it is worth
wondering if the replacement option will become more viable if the
domestic industry can make a greater commitment to quality and detail.
The cost of these imported custom window replacements is roughly equivalent to that of a fully restored historic window.
Paul Marlowe says that one needn't be a partisan advocate of historic
preservation to consider restoring historic wood windows as they hold their
own with regard to overall cost. In an environment where budget and schedule
can dictate choices, working with the restoration artisan is the most efficient
way to establish costs and options. He advises clients that it is useful
to look to the future when dealing with historic structures, regardless
of the budget. If present means can only support an inexpensive replacement
window, they are advised to preserve their options by labeling restorable
sash and safely storing it against the day when different circumstances
may apply. It will not pay to underestimate the long term value of this
irreplaceable historic fabric.
Window Restoration Specialists:
Weston Millwork Company, Weston MO, Custom historic window sash reproduction.
Marlowe Restorations, Northford CT, Carpentry & Wood Window Restoration, CT.
East End Wood Strippers, Holbrook NY, Interior wood stripping & refinishing.
Heather and Little, Ltd., Markham ON, Canada, Clad historic windows in sheet metal.
Honeoye Falls Millwork, Honeoye Falls NY, Custom Reproduction & Restoration of wood windows.
Landmark Services, Inc., Medway MA, Restoration and renovation, Southern New England.
Smith Restoration Sash, Providence RI, Custom window sash for restoration, period glass and hardware.
Traditional Builders, Inc., Annapolis MD, Restoration & traditional home building, MD & VA.