Preservation Tech Notes: Windows 7 Window Awnings

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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

Last Reviewed 2012-02-24