Preservation Tech Notes: Windows 5 Interior Metal Storm Windows

Historic Preservation

Building Manager Tools

Historic Buildings

Historic Preservation Library

Portfolio Management Resources

Preservation Desk Guide

Preserve America

Project Management Tools

Realty Specialist Tools

Technical Resources

GSA Technical Preservation Guidelines

Historic Preservation Technical Procedures

NCR Preservation Note Series

Preservation Technology

Historic Preservation - Technical Procedures

Spectitle:	Preservation Tech Notes: Windows 5 Interior Metal Storm Windows
Procedure code:	0867003S
Source:	Preservation Tech Notes, National Park Service, Pad
Division:	Doors And Windows
Section:	Storm Windows
Last Modified:	02/24/2012
Details:	Preservation Tech Notes: Windows 5 Interior Metal Storm Windows PRESERVATION TECH NOTES: WINDOWS Number 5 INTERIOR METAL STORM WINDOWS 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. OLD WATKINS NATIONAL BANK Lawrence, Kansas *INTRODUCTION* The Old Watkins National Bank (now known as the Watkins Community Museum) is an impressive example of Richardsonian Romanesque architecture in Kansas. Built in 1887, the building is individually listed on the National Register of Historic Places and is owned by the Douglas County Historical Society. The windows are a prominent feature of the building. The 102 windows, a majority of which are 5' wide by 10' high, are in twelve sizes and five styles. Many have arched tops. The monumental double-hung windows help to convey the grand qualities of the original design both on the exterior and in the spacious interior. Made of curly and burly pine, the windows are exquisitely trimmed on the interior, and the distinctive natural wood grain is especially pronounced in the jamb panels and interior shutters. Unlike the more usual shutters which fold against the jamb, these shutters slide vertically within multiple jamb tracks. *DESIGN PROBLEM* As with most building owners, the historical society was concerned about energy usage and thermal comfort as well as the need to have closely regulated environmental control to protect museum collections. As part of an overall rehabilitation program, an energy audit was initially performed by the local utility company. Although the historic wood windows were well-constructed and not seriously deteriorated, they were identified as a major contributor to energy usage because of their number and large sizes. Single glazing, lack of weather stripping and cracks around the window frames all added to winter heat loss, summer heat gain and appreciable air infiltration. As a result of the energy audit, the project architect, James Williams AIA, investigated several storm window systems. Use of exterior storm windows was initially explored both for energy conservation purposes and as a way to extend the useful life of the original windows. Unfortunately, the prices quoted for exterior storm windows by local contractors were around $65,000, nearly double the budgeted amount. In addition to the high cost of exterior storm windows, one further problem with an exterior storm application arose when it was discovered that the decorative terra- cotta capitals adjacent to the upper level window openings returned against the original frames. As a result, the proposed exterior storm windows could not be easily installed in these locations without cutting back or covering portions of the terra cotta. The numerous problems with exterior storm windows encountered in this project led to consideration of an interior storm system. Here too, there were specific requirements: 1. The impressive interior woodwork around the windows could not be damaged. 2. The new window unit could not alter the appearance of the windows as viewed from the outside and the basic character of the window needed to be preserved on the inside as well. 3. The storm window needed to have venting capability in case condensation occurred between the storm unit and the original sash to protect against damage to the original sill. 4. The windows needed to be less expensive than the exterior storm windows. 5. The interior shutter system still used in various rooms for sun control needed to remain operable. 6. The energy conservation objectives would have to be met. *DESIGN SOLUTION* In searching for an interior storm window that met both the functional requirements and the concerns about visual qualities, the architect chose a commercially available metal storm window system. The storm window was designed to fit within the existing wooden jamb, thus resulting in minimal damage to historic material. The interior windows were nearly $20,000 cheaper to install than the bids received for exterior storm windows. Of particular significance, the storm sash were not readily visible from the outside, and on the inside the thin bronze-finished frames blended in well with the decorative finish and fine detailing of the original windows. Selecting an interior storm window per se had certain inherent advantages in this case over exterior applications: (1) no obtrusive structural muntins were necessary because wind pressure was not a major factor; (2) fabrication of the storm windows on the first floor was significantly less expensive since the original windows were squared-off at the head on the interior unlike the arch shape found on the exterior; and (3) installation costs would be appreciably lower since problems created by cutting back the decorative terra cotta capitals on the exterior of the second floor openings were avoided. *STORM WINDOW DETAIL* The thin aluminum storm window frame (7/8" wide, 1-1/2" deep) was attached to a small new subframe by two pins that allowed the windows to pivot open for cleaning and venting in case entrapped condensation was ever a problem. The subframe consisted of a 1/8" thick metal angle screwed to the wood jamb, serving as a support and as a stop for the storm sash. On the large windows, the metal angle was paired to form a horizontal muntin, in line with the historic meeting rail, to accommodate an upper and lower storm panel, both of which pivoted. The frames were mounted in a location that provided a sufficiently wide dead air space for energy conservation purposes, yet still allowed the interior shutters to remain operable. Mounted on pivot pins, the storm window relied on the pile weather stripping which ran continuously along the edge of the frame to serve as the seal between the metal subframe and the metal storm. Neoprene weather stripping was also added to the surface of the subframe to serve as a compression seal with the storm frame. Clear silicone caulk between the wood jamb and the subframe completed the seal. *ASSEMBLY AND INSTALLATION* The frames were custom-fitted to each opening and prefabricated by a local glass dealer. For each of installation, the glazing was not done at this time. At the site, the sash frames were positioned in the existing jambs with the aid of a rolling scaffold. A space of nearly 1-3/4" was provided between the existing glass, which is in a very thick wood frame, and the back of the storm glass; this space serves as a dead air pocket for energy conservation. To mount the frames, holes were drilled and hardware attached for the lock and pivot mechanisms; the storm frames were then attached and the loose end of the hold-open arms were screwed to the metal subframe. Once the glass was installed, the work was essentially completed. *PROJECT EVALUATION* The storm window system chosen for the building fulfilled the criteria established at the beginning of the project. Interior storm windows were installed on 92 of the windows in 1981 at a cost of $45,068 ($12.07 per square foot of opening), and an initial cost savings of nearly $20,000 was realized over exterior storm applications. A portion of the cost saving was attributed to the fact that, as interior storm windows, they were installed by the contractor during his slow winter months. The payback period for the storm windows will be accurately determined only by in-place performance. However, it would appear that the storm windows are reducing the energy consumption by more than 40% - a figure that exceeded the theoretical calculations. Long-term maintenance of the storm windows is expected to be low because of the quality of construction and because the windows will not be opened on a daily basis. Other benefits have resulted from this project cannot be directly measured in dollars. Former hot and cold spots in the building have been greatly reduced. Patron comfort has been noticeably improved both thermally and from reduced street noise level. In summary, the interior storm window solution not only provided the owner with initial cost savings in installation, but it also reduced fuel consumption, met all functional requirements, and carefully addressed historic preservation concerns. The thin frame storm window, set within the existing jamb and mounted so as to pivot, was a sensitive solution which is also being used on other projects involving rehabilitations of historically important commercial buildings. *PROJECT DATA* BUILDING: - Elizabeth M. Watkins Community Museum (formerly the Old Watkins National Bank 1047 Massachusetts Street Lawrence, Kansas PROJECT DATE: Winter 1981 PROJECT STAFF: - James Williams, AIA Project Architect 123 West Eight Lawrence, Kansas - Kennedy Glass, Inc. Contractor P. O. Box 681 Lawrence, Kansas - Steve Jansen Director, Watkins Community Museum Lawrence, Kansas SPECIAL SUPPLIES: - Interior Storm Windows - Kawneer Company, Inc. 1105 North Front Street Miles, Michigan PROJECT COSTS: - Total costs, including installation for the 92 storm windows was $45,068, equaling $12.07 per square foot. Small storm windows were up to four times as expensive per square foot as the largest ones. Units were not installed on 6 attic and 4 basement windows. END OF SECTION

Last Reviewed 2012-02-24