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The Repair of Historic Wooden
Windows
John H. Myers
The windows on many historic buildings are an important aspect of
the architectural character of those buildings. Their design, craftsmanship,
or other qualities may make them worthy of preservation. This is self-evident
for ornamental windows, but it can be equally true for warehouses or
factories where the windows may be the most dominant visual element
of an otherwise plain building (see figure 1). Evaluating the significance
of these windows and planning for their repair or replacement can be
a complex process involving both objective and subjective considerations.
The Secretary of the Interior's Standards for Rehabilitation and the
accompanying guidelines, call for respecting the significance of original
materials and features, repairing and retaining them wherever possible,
and when necessary, replacing them in kind. This Brief is based on the
issues of significance and repair which are implicit in the standards,
but the primary emphasis is on the technical issues of planning for
the repair of windows including evaluation of their physical condition,
techniques of repair, and design considerations when replacement is
necessary.
Much of the technical section presents repair
techniques as an instructional guide for the do-it-yourselfer. The information
will be useful, however, for the architect, contractor, or developer
on large-scale projects. It presents a methodology for approaching the
evaluation and repair of existing windows, and considerations for replacement,
from which the professional can develop alternatives and specify appropriate
materials and procedures.
Architectural
or Historical Significance
Evaluating the architectural or historical significance
of windows is the first step in planning for window treatments, and
a general understanding of the function and history of windows is vital
to making a proper evaluation. As a part of this evaluation, one must
consider four basic window functions: admitting light to the interior
spaces, providing fresh air and ventilation to the interior, providing
a visual link to the outside world, and enhancing the appearance of
a building. No single factor can be disregarded when planning window
treatments; for example, attempting to conserve energy by closing up
or reducing the size of window openings may result in the use of more
energy by increasing electric lighting loads and decreasing passive
solar heat gains.
Historically, the first windows in early American
houses were casement windows; that is, they were hinged at the side
and opened outward. In the beginning of the eighteenth century single-
and double-hung windows were introduced. Subsequently many styles of
these vertical sliding sash windows have come to be associated with
specific building periods or architectural styles, and this is an important
consideration in determining the significance of windows, especially
on a local or regional basis. Site-specific, regionally oriented architectural
comparisons should be made to determine the significance of windows
in question. Although such comparisons may focus on specific window
types and their details, the ultimate determination of significance
should be made within the context of the whole building, wherein the
windows are one architectural element (see figure 2).
After all of the factors have been evaluated,
windows should be considered significant to a building if they: 1) are
original, 2) reflect the original design intent for the building, 3)
reflect period or regional styles or building practices, 4) reflect
changes to the building resulting from major periods or events, or 5)
are examples of exceptional craftsmanship or design. Once this evaluation
of significance has been completed, it is possible to proceed with planning
appropriate treatments, beginning with an investigation of the physical
condition of the windows.
Physical
Evaluation
The key to successful planning for window treatments
is a careful evaluation of existing physical conditions on a unit-by-unit
basis. A graphic or photographic system may be devised to record existing
conditions and illustrate the scope of any necessary repairs. Another
effective tool is a window schedule which lists all of the parts of
each window unit. Spaces by each part allow notes on existing conditions
and repair instructions. When such a schedule is completed, it indicates
the precise tasks to be performed in the repair of each unit and becomes
a part of the specifications. In any evaluation, one should note at
a minimum, 1) window location, 2) condition of the paint, 3) condition
of the frame and sill, 4) condition of the sash (rails, stiles and muntins),
5) glazing problems, 6) hardware, and 7) the overall condition of the
window (excellent, fair, poor, and so forth).
Many factors such as poor design, moisture, vandalism,
insect attack, and lack of maintenance can contribute to window deterioration,
but moisture is the primary contributing factor in wooden window decay.
All window units should be inspected to see if water is entering around
the edges of the frame and, if so, the joints or seams should be caulked
to eliminate this danger. The glazing putty should be checked for cracked,
loose, or missing sections which allow water to saturate the wood, especially
at the joints. The back putty on the interior side of the pane should
also be inspected, because it creates a seal which prevents condensation
from running down into the joinery. The sill should be examined to insure
that it slopes downward away from the building and allows water to drain
off. In addition, it may be advisable to cut a dripline along the underside
of the sill. This almost invisible treatment will insure proper water
runoff, particularly if the bottom of the sill is flat.
Any conditions, including poor original design, which permit water to
come in contact with the wood or to puddle on the sill must be corrected
as they contribute to deterioration of the window.
One clue to the location of areas of excessive
moisture is the condition of the paint; therefore, each window should
be examined for areas of paint failure. Since excessive moisture is
detrimental to the paint bond, areas of paint blistering, cracking,
flaking, and peeling usually identify points of water penetration, moisture
saturation, and potential deterioration. Failure of the paint should
not, however, be mistakenly interpreted as a sign that the wood is in
poor condition and hence, irreparable. Wood is frequently in sound physical
condition beneath unsightly paint. After noting areas of paint failure,
the next step is to inspect the condition of the wood, particularly
at the points identified during the paint examination.
Each window should be examined for operational
soundness beginning with the lower portions of the frame and sash. Exterior
rainwater and interior condensation can flow downward along the window,
entering and collecting at points where the flow is blocked. The sill,
joints between the sill and jamb, corners of the bottom rails and muntin
joints are typical points where water collects and deterioration begins
(see figure 3). The operation of the window (continuous opening and
closing over the years and seasonal temperature changes) weakens the
joints, causing movement and slight separation. This process makes the
joints more vulnerable to water which is readily absorbed into the endgrain
of the wood. If severe deterioration exists in these areas, it will
usually be apparent on visual inspection, but other less severely deteriorated
areas of the wood may be tested by two traditional methods using a small
ice pick.
An ice pick or an awl may be used to test wood
for soundness. The technique is simply to jab the pick into a wetted
wood surface at an angle and pry up a small section of the wood. Sound
wood will separate in long fibrous splinters, but decayed wood will
lift up in short irregular pieces due to the breakdown of fiber strength.
Another method of testing for soundness consists
of pushing a sharp object into the wood, perpendicular to the surface.
If deterioration has begun from the hidden side of a member and the
core is badly decayed, the visible surface may appear to be sound wood.
Pressure on the probe can force it through an apparently sound skin
to penetrate deeply into decayed wood. This technique is especially
useful for checking sills where visual access to the underside is restricted.
Following the inspection and analysis of the results,
the scope of the necessary repairs will be evident and a plan for the
rehabilitation can be formulated. Generally the actions necessary to
return a window to "like new" condition will fall into three broad categories:
1) routine maintenance procedures, 2) structural stabilization, and
3) parts replacement. These categories will be discussed in the following
sections and will be referred to respectively as Repair Class I, Repair
Class II, and Repair Class III. Each successive repair class represents
an increasing level of difficulty, expense, and work time. Note that
most of the points mentioned in Repair Class I are routine maintenance
items and should be provided in a regular maintenance program for any
building. The neglect of these routine items can contribute to many
common window problems.
Before undertaking any of the repairs mentioned
in the following sections all sources of moisture penetration should
be identified and eliminated, and all existing decay fungi destroyed
in order to arrest the deterioration process. Many commercially available
fungicides and wood preservatives are toxic, so it is extremely important
to follow the manufacturer's recommendations for application, and store
all chemical materials away from children and animals. After fungicidal
and preservative treatment the windows may be stabilized, retained,
and restored with every expectation for a long service life.
Repair
Class I: Routine Maintenance
Repairs to wooden windows are usually labor intensive
and relatively uncomplicated. On small scale projects this allows the
do-it-yourselfer to save money by repairing all or part of the windows.
On larger projects it presents the opportunity for time and money which
might otherwise be spent on the removal and replacement of existing
windows, to be spent on repairs, subsequently saving all or part of
the material cost of new window units. Regardless of the actual costs,
or who performs the work, the evaluation process described earlier will
provide the knowledge from which to specify an appropriate work program,
establish the work element priorities, and identify the level of skill
needed by the labor force.
The routine maintenance required to upgrade a
window to "like new" condition normally includes the following steps:
1) some degree of interior and exterior paint removal, 2) removal and
repair of sash (including reglazing where necessary), 3) repairs to
the frame, 4) weatherstripping and reinstallation of the sash, and 5)
repainting. These operations are illustrated for a typical double-hung
wooden window (see figures 4a-f), but they may be adapted to other window
types and styles as applicable.
Historic windows have usually acquired many layers
of paint over time. Removal of excess layers or peeling and flaking
paint will facilitate operation of the window and restore the clarity
of the original detailing. Some degree of paint removal is also necessary
as a first step in the proper surface preparation for subsequent refinishing
(if paint color analysis is desired, it should be conducted prior to
the onset of the paint removal). There are several safe and effective
techniques for removing paint from wood, depending on the amount of
paint to be removed. Several techniques such as scraping, chemical stripping,
and the use of a hot air gun are discussed in "Preservation Briefs:
10 Paint Removal from Historic Woodwork" (see Additional Reading section
at end).
Paint removal should begin on the interior frames,
being careful to remove the paint from the interior stop and the parting
bead, particularly along the seam where these stops meet the jamb. This
can be accomplished by running a utility knife along the length of the
seam, breaking the paint bond. It will then be much easier to remove
the stop, the parting bead and the sash. The interior stop may be initially
loosened from the sash side to avoid visible scarring of the wood and
then gradually pried loose using a pair of putty knives, working up
and down the stop in small increments (see figure 4b). With the stop
removed, the lower or interior sash may be withdrawn. The sash cords
should be detached from the sides of the sash and their ends may be
pinned with a nail or tied in a knot to prevent them from falling into
the weight pocket.
Removal of the upper sash on double-hung units
is similar but the parting bead which holds it in place is set into
a groove in the center of the stile and is thinner and more delicate
than the interior stop. After removing any paint along the seam, the
parting bead should be carefully pried out and worked free in the same
manner as the interior stop. The upper sash can be removed in the same
manner as the lower one and both sash taken to a convenient work area
(in order to remove the sash the interior stop and parting bead need
only be removed from one side of the window). Window openings can be
covered with polyethylene sheets or plywood sheathing while the sash
are out for repair.
The sash can be stripped of paint using appropriate
techniques, but if any heat treatment is used (see figure 4c), the glass
should be removed or protected from the sudden temperature change which
can cause breakage. An overlay of aluminum foil on gypsum board or asbestos
can protect the glass from such rapid temperature change. It is important
to protect the glass because it may be historic and often adds character
to the window. Deteriorated putty should be removed manually, taking
care not to damage the wood along the rabbet. If the glass is to be
removed, the glazing points which hold the glass in place can be extracted
and the panes numbered and removed for cleaning and reuse in the same
openings. With the glass panes out, the remaining putty can be removed
and the sash can be sanded, patched, and primed with a preservative
primer. Hardened putty in the rabbets may be softened by heating with
a soldering iron at the point of removal. Putty remaining on the glass
may be softened by soaking the panes in linseed oil, and then removed
with less risk of breaking the glass. Before reinstalling the glass,
a bead of glazing compound or linseed oil putty should be laid around
the rabbet to cushion and seal the glass. Glazing compound should only
be used on wood which has been brushed with linseed oil and primed with
an oil based primer or paint. The pane is then pressed into place and
the glazing points are pushed into the wood around the perimeter of
the pane (see figure 4d). The final glazing compound or putty is applied
and beveled to complete the seal. The sash can be refinished as desired
on the inside and painted on the outside as soon as a "skin" has formed
on the putty, usually in 2 or 3 days. Exterior paint should cover the
beveled glazing compound or putty and lap over onto the glass slightly
to complete a weather-tight seal. After the proper curing times have
elapsed for paint and putty, the sash will be ready for reinstallation.
While the sash are out of the frame, the condition
of the wood in the jamb and sill can be evaluated. Repair and refinishing
of the frame may proceed concurrently with repairs to the sash, taking
advantage of the curing times for the paints and putty used on the sash.
One of the most common work items is the replacement of the sash cords
with new rope cords or with chains (see figure 4e). The weight pocket
is frequently accessible through a door on the face of the frame near
the sill, but if no door exists, the trim on the interior face may be
removed for access. Sash weights may be increased for easier window
operation by elderly or handicapped persons. Additional repairs to the
frame and sash may include consolidation or replacement of deteriorated
wood. Techniques for these repairs are discussed in the following sections.
The operations just discussed summarize the efforts
necessary to restore a window with minor deterioration to "like new"
condition (see figure 4f). The techniques can be applied by an unskilled
person with minimal training and experience. To demonstrate the practicality
of this approach, and photograph it, a Technical Preservation Services
staff member repaired a wooden double-hung, two over two window which
had been in service over ninety years. The wood was structurally sound
but the window had one broken pane, many layers of paint, broken sash
cords and inadequate, worn-out weatherstripping. The staff member found
that the frame could be stripped of paint and the sash removed quite
easily. Paint, putty and glass removal required about one hour for each
sash, and the reglazing of both sash was accomplished in about one hour.
Weatherstripping of the sash and frame, replacement of the sash cords
and reinstallation of the sash, parting bead, and stop required an hour
and a half. These times refer only to individual operations; the entire
process took several days due to the drying and curing times for putty,
primer, and paint, however, work on other window units could have been
in progress during these
lag times.
Repair
Class II: Stabilization
The preceding description of a window repair job
focused on a unit which was operationally sound. Many windows will show
some additional degree of physical deterioration, especially in the
vulnerable areas mentioned earlier, but even badly damaged windows can
be repaired using simple processes. Partially decayed wood can be waterproofed,
patched, built-up, or consolidated and then painted to achieve a sound
condition, good appearance, and greatly extended life. Three techniques
for repairing partially decayed or weathered wood are discussed in this
section, and all three can be accomplished using products available
at most hardware stores.
One established technique for repairing wood which
is split, checked or shows signs of rot, is to: 1) dry the wood, 2)
treat decayed areas with a fungicide, 3) waterproof with two or three
applications of boiled linseed oil (applications every 24 hours), 4)
fill cracks and holes with putty, and 5) after a "skin" forms on the
putty, paint the surface. Care should be taken with the use of fungicide
which is toxic. Follow the manufacturers' directions and use only on
areas which will be painted. When using any technique of building up
or patching a flat surface, the finished surface should be sloped slightly
to carry water away from the window and not allow it to puddle. Caulking
of the joints between the sill and the jamb will help reduce further
water penetration.
When sills or other members exhibit surface weathering
they may also be built-up using wood putties or homemade mixtures such
as sawdust and resorcinol glue, or whiting and varnish. These mixtures
can be built up in successive layers, then sanded, primed, and painted.
The same caution about proper slope for flat surfaces applies to this
technique.
Wood may also be strengthened and stabilized by
consolidation, using semirigid epoxies which saturate the porous decayed
wood and then harden. The surface of the consolidated wood can then
be filled with a semirigid epoxy patching compound, sanded and painted
(see figure 5). Epoxy patching compounds can be used to build up missing
sections or decayed ends of members. Profiles can be duplicated using
hand molds, which are created by pressing a ball of patching compound
over a sound section of the profile which has been rubbed with butcher's
wax. This can be a very efficient technique where there are many typical
repairs to be done. Technical Preservation Services has published Epoxies
for Wood Repairs in Historic Buildings (see Additional Reading section
at end), which discusses the theory and techniques of epoxy repairs.
The process has been widely used and proven in marine applications;
and proprietary products are available at hardware and marine supply
stores. Although epoxy materials may be comparatively expensive, they
hold the promise of being among the most durable and long lasting materials
available for wood repair.
Any of the three techniques discussed can stabilize
and restore the appearance of the window unit. There are times, however,
when the degree of deterioration is so advanced that stabilization is
impractical, and the only way to retain some of the original fabric
is to replace damaged parts.
Repair
Class III: Splices and Parts Replacement
When parts of the frame or sash are so badly deteriorated
that they cannot be stabilized there are methods which permit the retention
of some of the existing or original fabric. These methods involve replacing
the deteriorated parts with new matching pieces, or splicing new wood
into existing members. The techniques require more skill and are more
expensive than any of the previously discussed alternatives. It is necessary
to remove the sash and/or the affected parts of the frame and have a
carpenter or woodworking mill reproduce the damaged or missing parts.
Most millwork firms can duplicate parts, such as muntins, bottom rails,
or sills, which can then be incorporated into the existing window, but
it may be necessary to shop around because there are several factors
controlling the practicality of this approach. Some woodworking mills
do not like to repair old sash because nails or other foreign objects
in the sash can damage expensive knives (which cost far more than their
profits on small repair jobs); others do not have cutting knives to
duplicate muntin profiles. Some firms prefer to concentrate on larger
jobs with more profit potential, and some may not have a craftsman who
can duplicate the parts. A little searching should locate a firm which
will do the job, and at a reasonable price. If such a firm does not
exist locally, there are firms which undertake this kind of repair and
ship nationwide. It is possible, however, for the advanced do-it-yourselfer
or craftsman with a table saw to duplicate moulding profiles using techniques
discussed by Gordie Whittington in "Simplified Methods for Reproducing
Wood Mouldings," Bulletin of the Association for Preservation Technology,
Vol. III, No. 4, 1971, or illustrated more recently in The Old House,
TimeLife Books, Alexandria, Virginia, 1979.
The repairs discussed in this section involve
window frames which may be in very deteriorated condition, possibly
requiring removal; therefore, caution is in order. The actual construction
of wooden window frames and sash is not complicated. Pegged mortise
and tenon units can be disassembled easily, if the units are out of
the building. The installation or connection of some frames to the surrounding
structure, especially masonry walls, can complicate the work immeasurably,
and may even require dismantling of the wall. It may be useful, therefore,
to take the following approach to frame repair: 1) conduct regular maintenance
of sound frames to achieve the longest life possible, 2) make necessary
repairs in place wherever possible, using stabilization and splicing
techniques, and 3) if removal is necessary, thoroughly investigate the
structural detailing and seek appropriate professional consultation.
Another alternative may be considered if parts
replacement is required, and that is sash replacement. If extensive
replacement of parts is necessary and the job becomes prohibitively
expensive it may be more practical to purchase new sash which can be
installed into the existing frames. Such sash are available as exact
custom reproductions, reasonable facsimiles (custom windows with similar
profiles), and contemporary wooden sash which are similar in appearance.
There are companies which still manufacture high quality wooden sash
which would duplicate most historic sash. A few calls to local building
suppliers may provide a source of appropriate replacement sash, but
if not, check with local historical associations, the state historic
preservation office, or preservation related magazines and supply catalogs
for information.
If a rehabilitation project has a large number
of windows such as a commercial building or an industrial complex, there
may be less of a problem arriving at a solution. Once the evaluation
of the windows is completed and the scope of the work is known, there
may be a potential economy of scale. Woodworking mills may be interested
in the work from a large project; new sash in volume may be considerably
less expensive per unit; crews can be assembled and trained on site
to perform all of the window repairs; and a few extensive repairs can
be absorbed (without undue burden) into the total budget for a large
number of sound windows. While it may be expensive for the average historic
home owner to pay seventy dollars or more for a mill to grind a custom
knife to duplicate four or five bad muntins, that cost becomes negligible
on large commercial projects which may have several hundred windows.
Most windows should not require the extensive
repairs discussed in this section. The ones which do are usually in
buildings which have been abandoned for long periods or have totally
lacked maintenance for years. It is necessary to thoroughly investigate
the alternatives for windows which do require extensive repairs to arrive
at a solution which retains historic significance and is also economically
feasible. Even for projects requiring repairs identified in this section,
if the percentage of parts replacement per window is low, or the number
of windows requiring repair is small, repair can still be a cost effective
solution.
Weatherization
A window which is repaired should be made as energy
efficient as possible by the use of appropriate weatherstripping to
reduce air infiltration. A wide variety of products are available to
assist in this task. Felt may be fastened to the top, bottom, and meeting
rails, but may have the disadvantage of absorbing and holding moisture,
particularly at the bottom rail. Rolled vinyl strips may also be tacked
into place in appropriate locations to reduce infiltration. Metal strips
or new plastic spring strips may be used on the rails and, if space
permits, in the channels between the sash and jamb. Weatherstripping
is a historic treatment, but old weatherstripping (felt) is not likely
to perform very satisfactorily. Appropriate contemporary weatherstripping
should be considered an integral part of the repair process for windows.
The use of sash locks installed on the meeting rail will insure that
the sash are kept tightly closed so that the weatherstripping will function
more effectively to reduce infiltration. Although such locks will not
always be historically accurate, they will usually be viewed as an acceptable
contemporary modification in the interest of improved thermal performance.
Many styles of storm windows are available to
improve the thermal performance of existing windows. The use of exterior
storm windows should be investigated whenever feasible because they
are thermally efficient, cost-effective, reversible, and allow the retention
of original windows (see "Preservation Briefs: 3"). Storm window frames
may be made of wood, aluminum, vinyl, or plastic; however, the use of
unfinished aluminum storms should be avoided. The visual impact of storms
may be minimized by selecting colors which match existing trim color.
Arched top storms are available for windows with special shapes. Although
interior storm windows appear to offer an attractive option for achieving
double glazing with minimal visual impact, the potential for damaging
condensation problems must be addressed. Moisture which becomes trapped
between the layers of glazing can condense on the colder, outer prime
window, potentially leading to deterioration. The correct approach to
using interior storms is to create a seal on the interior storm while
allowing some ventilation around the prime window. In actual practice,
the creation of such a durable, airtight seal is difficult.
Window
Replacement
Although the retention of original or existing
windows is always desirable and this Brief is intended to encourage
that goal, there is a point when the condition of a window may clearly
indicate replacement. The decision process for selecting replacement
windows should not begin with a survey of contemporary window products
which are available as replacements, but should begin with a look at
the windows which are being replaced. Attempt to understand the contribution
of the window(s) to the appearance of the facade including: 1) the pattern
of the openings and their size; 2) proportions of the frame and sash;
3) configuration of window panes; 4) muntin profiles; 5) type of wood;
6) paint color; 7) characteristics of the glass; and 8) associated details
such as arched tops, hoods, or other decorative elements. Develop an
understanding of how the window reflects the period, style, or regional
characteristics of the building, or represents technological development.
Armed with an awareness of the significance of
the existing window, begin to search for a replacement which retains
as much of the character of the historic window as possible. There are
many sources of suitable new windows. Continue looking until an acceptable
replacement can be found. Check building supply firms, local woodworking
mills, carpenters, preservation oriented magazines, or catalogs or suppliers
of old building materials, for product information. Local historical
associations and state historic preservation offices may be good sources
of information on products which have been used successfully in preservation
projects.
Consider energy efficiency as one of the factors
for replacements, but do not let it dominate the issue. Energy conservation
is no excuse for the wholesale destruction of historic windows which
can be made thermally efficient by historically and aesthetically acceptable
means. In fact, a historic wooden window with a high quality storm window
added should thermally outperform a new double-glazed metal window which
does not have thermal breaks (insulation between the inner and outer
frames intended to break the path of heat flow). This occurs because
the wood has far better insulating value than the metal, and in addition
many historic windows have high ratios of wood to glass, thus reducing
the area of highest heat transfer. One measure of heat transfer is the
U-value, the number of Btu's per hour transferred through a square foot
of material. When comparing thermal performance, the lower the U-value
the better the performance. According to ASHRAE 1977 Fundamentals, the
U-values for single glazed wooden windows range from 0.88 to 0.99. The
addition of a storm window should reduce these figures to a range of
0.44 to 0.49. A non-thermal break, double-glazed metal window has a
U-value of about 0.6.
Conclusion
Technical Preservation Services recommends the
retention and repair of original windows whenever possible. We believe
that the repair and weatherization of existing wooden windows is more
practical than most people realize, and that many windows are unfortunately
replaced because of a lack of awareness of techniques for evaluation,
repair, and weatherization. Wooden windows which are repaired and properly
maintained will have greatly extended service lives while contributing
to the historic character of the building. Thus, an important element
of a building's significance will have been preserved for the future.
Additional Reading
ASHRAE Handbook1977 Fundamentals. New York: American
Society of Heating, Refrigerating and Air-conditioning Engineers, 1978
(chapter 26).
Ferro, Maximillian. Preservation: Present Pathway
to Fall River's Future. Fall River, Massachusetts: City of Fall River,
1979 (chapter 7).
"Fixing Double-hung Windows." Old House
Journal (no. 12, 1979): 135.
Look, David W. "Preservation Briefs: 10 Paint
Removal from Historic Woodwork." Washington, DC: Technical Preservation
Services, U.S. Department of the Interior, forthcoming.
Morrison, Hugh. Early American Architecture. New
York: Oxford University Press, 1952.
Phillips, Morgan, and Selwyn, Judith. Epoxies
for Wood Repairs in Historic Buildings. Washington, DC: Technical Preservation
Services, U.S. Department of the Interior (Government Printing Office,
Stock No. 024016000951), 1978.
Rehab Right. Oakland, California: City of Oakland
Planning Department, 1978 (pp. 7883).
"Sealing Leaky Windows." Old House Journal
(no. 1, 1973): 5.
Smith, Baird M. "Preservation Briefs: 3 Conserving
Energy in Historic Buildings." Washington, DC: Technical Preservation
Services, U.S. Department of the Interior, 1978.
Washington, D.C. 1981.
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