Skip to main content

Historic Preservation - Technical Procedures

Spectitle:

Preservation Tech Notes: Windows 7 Window Awnings

Procedure code:

0877001S

Source:

Preservation Tech Notes, National Park Service, Pad

Division:

Doors And Windows

Section:

Door & Window Accessories

Last Modified:

02/24/2012

Details:

Preservation Tech Notes: Windows 7 Window Awnings



PRESERVATION TECH NOTES:  WINDOWS Number 7

WINDOW AWNINGS

Laura A. Muckenfuss
Center for Architectural Conservation
Georgia Institute of Technology

and

Charles E. Fisher
Preservation Assistance Division
National Park Service


This standard includes the bulk of information contained in the
original Preservation Tech Notes developed by the National Park
Service and the Center for Architectural Conservation at Georgia
Tech.  The Preservation Tech Notes are case studies of exemplary
projects designed to provide specific examples of sound
preservation techniques.  To obtain a complete copy of The Window
publications, including figures and illustrations, please contact:

         Historic Preservation Education Foundation
         P.O. Box 77160
         Washington, DC  20013-7160

The Window Handbook, jointly prepared by the National Park Service,
Preservation Assistance Division and the Center for Architectural
Conservation at Georgia Tech, also contains all of the Tech Notes
on Windows and is available for purchase from the Historic
Preservation Education Foundation for $32.00.  The Window Workbook
is available for $49.00.  The two publications together can be
purchased for $72.00.


FLORIDA STATE CAPITOL
Tallahassee, Florida

***INTRODUCTION***

The old Florida State Capitol, constructed in the 1840s and greatly
enlarged over the years, has recently been rehabilitated for use as
museum space and government offices.  The neo-classical revival
building has been returned to its 1902 appearance and is
individually listed in the National Register of Historic Places.

Photographs in the Florida Photographic Archives show that as early
as the 1890s, decorative awnings had been installed, replacing
shutters as sun screens.  Wide-striped red and white operable
awnings can be seen in postcards as early as 1902.  By World War
II, air conditioning units had been added to the building and the
awnings had been removed.

When rehabilitation plans were drawn up for the building, the
initial intention was not to duplicate the awnings.  Energy
studies, however, showed that significant cost savings could be
achieved by installing the awnings and today the building stands
with this highly colorful feature added.


***REHABILITATION DESIGN PROBLEM***

The effective use of awnings to reduce solar heat gain can be found
on numerous historic buildings during the late 19th and early 20th
centuries and it still is a treatment with practical applications
in certain climates.  In hot climates awnings can:

    -    Eliminate the need to alter or replace existing historic
         windows for reasons of improved energy performance while
         also reducing glare.

    -    Provide rain protection for windows opened for
         ventilation.

    -    Bring a bright, cheerful addition to a building.

Given the high visibility of such a window treatment, research
should be undertaken to ensure that awnings previously had been
used on the building.  Care should be taken to match the size,
design, color, and basic appearance of the historic awnings, where
possible.

The Florida State Capitol project is a good example where
replication of the awning treatment was undertaken primarily
because of the cost savings realized through reduced energy usage.

The architect and the mechanical engineer for the work at the
Capitol were concerned from the outset about the high cooling load
created by the large glass area on the building's facade.  The
cooling load required to handle the solar gain from the 138 windows
that measured 4' by 10' each was calculated at 55 tons.  There were
also significant air infiltration problems due to a lack of
weatherstripping and window maintenance.  It was estimated that
mechanical equipment with a capacity of 102 tons refrigeration
(which includes the 55 ton load for just the windows) would be
needed to cool the 46,501 square feet of building area and concern
was expressed that the air velocity from such a system might have
created drafty conditions in the smaller offices within the
building.  An engineering study of two offices on the west facade
of the building showed that 72% of the required cooling load in a
typical first floor office and 56% of the load in a typical second
floor office was due to exposed glass surface.  With the windows
contributing to 54% of the overall air conditioning load, some
measures were necessary to reduce the heat gain from the windows.

Some of the sash were in good condition and it would have been
possible to add tinted heat-absorbing insulating glass by rabbeting
out the existing sash frames.  Alternatively, tinted glass could
have been installed both in existing sash that were repairable as
well as in the numerous sash replacement units needed.  There were
concerns, however, over such visual changes to the historic
appearance of the building. Finally, cost considerations were an
important factor weighing against the use of insulating and new
tinted glass.  Rising energy costs and the savings from the
reduction in the size of the HVAC system made the reinstallation of
the awnings both a practical and economical alternative.


***REHABILITATION DESIGN SOLUTION***

It was determined that installation of the awnings would
appreciably reduce heat gain and cut energy consumption during
Florida's long hot weather season and also enable the Capitol
project to remain within its $7 million budget.  This was possible,
despite the purchase cost of the awnings, in part because of the
cost savings resulting from the ability to reduce the size of the
HVAC system.  The size, shape and installation angle of the
original awnings as shown in the archival records were duplicated
in the new work.

Since the primary facades of the Capitol faced east and west,
awnings were needed on the two main floors on all but the north
side.  Solar heat gain, which originally would have consumed 54% of
the required cooling load, was not estimated to be 31.5% of the
equipment load and allowed a downsizing of the HVAC system by 25
tons.  In typical first floor offices, the exposed glass surface
would now only account for 46% of the required cooling load down
from 72%.  On the second floor, there was a similar change from 56%
down to 30%.


***FABRICATION AND INSTALLATION***

A decision had to be made on the type of material to be used for
the awnings.  Canvas awnings had been used on the building from the
1890s through the 1930s, but records showed that the canvas lasted
only three to four years in the Florida climate.  A modern material
of acrylic fibers with an eight-year life expectancy was selected
instead to reduce the long-term maintenance needs.  A local marine
products company was located that sold the acrylic fabric.

The awnings were fabricated to the architect's design of 4' wide by
4' deep, with a height of 8'1" and a 9 1/2" scalloped valance.  The
100% acrylic fabric has vertical stripes four inches apart.
Regrettably the production of the acrylic weave did not allow for
pure color separation and as a result the striping is, in reality,
red and a very light pink; still the impression of red and white is
maintained.

The awning fabric can be readily removed from the frame for
replacement and cleaning.  Standard galvanized steel awning frames
designed to draw vertically against the window frame were used.
Since the windows in the Capitol were sealed shut for
weatherization purposes and to keep a more constant load demand on
the HVAC system, the pivoting points on the standard frames were
easily made rigid, preventing retraction of the awnings.

The decision to fix the awnings in a fully opened position did have
some cost trade-offs, since solar gain through the windows during
the short cold weather season would have been desirable.  There
also would be an advantage to being able to adjust the awnings to
allow natural light when the rays of the sun were not directly
shining on the windows.  In addition, the viewing area through the
window would be reduced in the upper portions of the window.
Operable awnings could have been provided by having the mechanical
opening hardware extend through to the inside.  This more costly
feature was not selected for use in the Capitol.

The hardware for the awnings, including the anchors and attaching
devices, were primarily galvanized or zinc plated steel.  Prior to
installation, the contractor was required to examine the windows
and to correct any condition that might have prevented proper
installation of the awnings.


***COST***

Eighty-four awnings were purchased for the Capitol.  Eighty-two
were installed on the two main floors throughout all but the north
side of the building.  The remaining two were saved for replacement
needs.  The cost of material and installation was $26,500 -
approximately $315 per large window.  Along with the benefits of
energy savings as a result of reduced heat gain during the long
warm weather season, the awnings have eliminated the problem of
glare in the main ceremonial spaces of the building.  In certain
rooms, the awnings also have eliminated the need to purchase and
maintain interior shades or draperies.

The awnings are proving to be cost effective with a full payback
projected within 3 to 4 years (even counting the projected high
maintenance cost), largely because of the reduced energy
consumption and as a result of the downsizing of the HVAC system.


***PROJECT EVALUATION***

The Florida State Capitol project has shown that awnings can be an
effective means of reducing heat gain.  Commonly used in the past
as a passive design feature to keep a building cool, awnings have
received renewed interest in the 1980s because of their energy-
conserving qualities.

The use of the acrylic fabric as a substitute material for the
original cotton duck canvas avoided the problem of shrinking that
canvas exhibits.  Moreover, acrylic is not affected as badly by
mildew.  It is also anticipated that the reinstallation of the
awnings with their protective overhang will provide some additional
cost savings through extended life for the windows.

The decision to make the frames rigid to prevent retraction of the
awnings on the Florida State Capitol did prove to be unwise, since
seasonal high winds, exacerbated by large adjacent new
construction, caused greater damage than had been anticipated.  To
correct this condition, the windows, which had been screwed shut
and sealed, were easily reopened; the awnings were rigged so that
they can be drawn back in high winds and various sleeves and pins
were removed from the frames, returning them to their original
operable condition.  Now whenever inclement weather is anticipated
or more sunlight is required in certain rooms, maintenance
personnel can easily retract the awnings.  The awnings now are
performing admirably and this highly distinctive historic feature
has generated considerable local interest.


***PROJECT DATA***

BUILDING:

-    Old Florida State Capitol
    Capitol Complex
    Tallahassee, Florida

OWNER:

-    State of Florida

PROJECT DATE:  1979-1982

PROJECT TEAM:

-    Herschel E. Shepard. FAIA
    Restoration Architect
    Shepard Associates, Inc.
    Jacksonville, Florida

-    James M. Hammond
    Mechanical Engineer
    Evans and Hammond, Inc.
    Jacksonville, Florida

-    Jennings Knox
    Project Manager
    Jack Culpepper Construction Company
    Tallahassee, Florida

-    C. E. Sullivan
    Manager
    Division of Building Construction and Property Management
    Department of General Services
    State of Florida
    Tallahassee, Florida

-    Florida Bureau of Historic Preservation
    Preservation Consultants
    Division of Archives, History and Records Management
    Department of State
    State of Florida

MATERIALS:

-    Awning Fabric and Hardware - Jacksonville Ship Chandlery
    Jacksonville, Florida

PROJECT COSTS:

-    The 84 awnings cost $26,500; approximately $315 apiece
    fabricated and installed.

                             END OF SECTION