|Army-Vermont Study Results:
Annual Heat Cost Savings
|Assuming your house already has wood windows with storm windows installed, how much would you save each year in heating and cooling costs by replacing your existing wndow/storm window combination with…||Annual Savings Per Window|
|…new single pane windows and new storm window?||0.00|
|…new single pane windows with low-E coating and new storm window?||$2.57|
|…new double pane thermal windows?|
(This option actually costs money.)
|…new double pane thermal windows with low-E coating?||$4.45|
|How Long to Pay Back Your Replacement Window Investment?|
According to the Haberern study, the most cost-effective option, with a payback in 4.5 years, was simply adding a good storm window to the existing single pane window. The worst option is replacing a single-pane window that already has a storm window with a new double-pane thermal window. This option had a payback of 240 years.
The most interesting finding was that a single pane/storm window combination with a U-value of 0.50 (R-Value=2) slightly outperformed the basic double-pane thermal window with a U-value of 0.58 (R-value = 1.72).
|Cost*||Annual Energy Savings (BTU)||Annual Savings per Window||Payback Period (Years)|
|Add a storm window to a single-pane window|
|Replace a single-pane window with a double-pane thermal window|
|Replace a single-pane window with a double-pane thermal window with low-E glass|
|Replace single-pane window/storm window combination with a double-pane thermal window with low-E glass|
|* Costs include installation based on actual costs in New Jersey, including heating costs, at the time of the study.|
"The NFRC Condensation Resistance scale is 1 to 100, with a higher number representing more resistance to the formation of condensation. The Condensation Resistance rating is determined based on outside conditions of approximately -18°C (0°F) with a 6 m/s (15 mph) wind, and inside conditions of approximately 21°C (70°F) with relative humidities of 30%, 50%, and 70% taken into consideration. The Condensation Resistance rating is a value that considers the relative area under condensation at these three humidity levels, which are then normalized, and the degree to which the surface temperatures are below the dew point for the frame and for the glazing are taken into account. The Condensation Resistance rating specified in the NFRC rating is based on the lower of the frame, center-of-glazing, or edge-of-glazing values."More simply: The range is from 1 to 100, with a higher number indicating a higher resistance to condensation. The problem with the measure is that it is hard for the average window buyer to translate the result to the real world. A lot depends on the average humidity level in your house, and if you install new windows, the average humidity level is likely to rise because you have probably sealed a lot of old air leaks. So the risk of condensation also rises. Bummer!
|Thermal Conductivity of Common Materials|
|Conductivity of a material is determined by measuring how long it takes heat to move through a specified thickness of the material. This is more complex than it sounds since conductivity is affected by temperature, and by the specific composition of the material. Ordinary carbon, for example, is not a particularly good conductor, but Graphene, an allotrope of carbon, is the most conductive material so far discovered. Generally a material being tested is held at a specified uniform temperature to make results as universal as possible. The result of the test is a value called a Thermal Transfer Coefficient which reflects the general conductivity of the material. The higher the number, the more conductive the material is.|
|Material||Thermal Transfer Coefficient
|Graphene (The most conductive material)||600.000|
|Hardwood (oak, maple)||0.028|
|Mineral wool (insulation)||0.007|
|Plaster (wood lath)||0.049|
|Softwoods (fir, pine)||0.021|
Articles and Books
The National Trust for Historic Preservation: Windows "Have you ever wondered why there are no replacement fireplaces? Fireplaces with ill-fitting or missing dampers leak more heat than windows do, but salesmen don't leave flyers for new dampers in your mailbox, do they?" Learn the answer in this well-written and concise statement of why old windows should be preserved, and a scathing indictment of the practices of the replacement window industry.
John Leeke's Historic Homeworks. Has a number of helpful videos and articles on restoring old windows, and a discussion forum where you can ask questions and get helpful answers. If you are serious about restoring your windows, you will want to invest in Leeke's Save America's Windows book which is pretty much the old window bible, and has, among other useful information, a list of window restoration experts organized by region.
Beth Goulart, "How To Restore Sash Windows" Old House Journal.
Thomas Baker, "How to Repair Sash Windows" This Old House.
William T. Cox Jr., "Sash Window Clinic: Maintaining the Mechanics of Double-Hung Windows" Old House Journal.
John H. Myers, "Preservation Briefs 9: The Repair of Historic Wooden Windows". Technical Preservation Services, National Park Service., U.S. Department of the Interior.
John Michael Davis, "New Life for Old Double-Hung Windows" Fine Homebuilding
Understanding Energy-Efficient Windows. Fine Homebuilding, The Taunton Press.
Energy Savers: Tips on Saving Energy and Money at Home. U.s. Department of Energy. (PDF)
Do-It-Yourself Home Energy Assessments. U.S. Department of Energy.
Alvarez, Kimberly K. & John D. Alvarez II, AIA, "Restoring Our Appreciation of Historic Wood Windows: Making a Case for Restoration Versus Replacement", The Local Landmarket, Issue 11, March 2009. New York State Office of Parks, Recreation and Historic Preservation, Field Services Bureau, Division for Historic Preservation.
Window Repair and Weatherization Guidebook: A Handy Guide for Owners of Portland, Oregon Homes (PDF), Bosco Milligan Foundation/Architectural Heritage Center With support from the Irvington Community Association Portland, Oregon, ©2012.
Parts & Supplies
Some of these sources are not used to dealing with consumers, and expect you to know exactly what you want. Others, like Blain Hardware, even have technical support departments that can help you decide what you need.
Smith Restoration Sash. Hard to find traditional wood window hardware. Each part well illustrated and it use and installation explained. A valuable resource for both the novice and experienced window restorer. Our go-to guy for shash cord and chain. Also, buy a can of Butcher's Bowling Alley Wax. It may not improve your bowling score, but will make your windows slide easier. 401-954-9431.
Killian Hardware, Chestnut Hill, Philadelphia, Penna. Wm. A. Kilian Hardware Co. The digital age version of the old corner hardware store with its pot-bellied stove and nails in kegs, Killian is a full line hardware source for all things old, including an extensive selection of basic wood window hardware. It has things you won't see for sale elsewhere. 215-247-0945
SpencerWorks. Wood storm combination windows. All the functionality of a modern storm window combined with the heritage appearance of a tratidional wood storm window. 402-499-7848
AA Window Parts & Hardware, Carries parts for most spring balances, including complete replacement kits and specialized tools. If you have spring balances rather the the traditional iron shash weights in your windows, this is a source for repair or replacement parts. 800-804-0147.
All About Doors & Windows, has been serving homeowners, contractors, and everyone in between for over 35 years. The company offers a vast selection of parts and will work with you to get you what you need. Articles and videos on the site help navigate do-it-yourself projects with minimal hassle. 816-221-8543
Blaine Window Hardware has been the generally recoginzed leader in door and window hardware for several decades. 800-678-1919
Phelps Company designs and manufactures the finest traditional brass window hardware available. The product line includes brass sash pulleys, brass, bronze, and stainless steel sash chain, sash weights, brass sash locks and lifts, push out casement window hardware, ventilation locks, window spring bolts, transom hardware, screen and storm door latchsets, stainless steel storm/screen hangers, and more ... 802-257-4314