PH-79-06-2 -- Thermal Performance of Wood Windows and Doors

According to a recent study conducted by Architectural Record, energy conservation is one ofthe highest ranking considerations, nationwide, when designers select building materials fornew construction. Due to the energy crisis of 1974 and subsequent energy conservation codesand legislation, complete and detailed thermal performance data is being required for windowsand doors, for use in analyzing their contribution to the energy load of the exterior buildingenvelope. Much of this data is currently based on engineering calculation or glass performancetables.NWMA has conducted controlled laboratory testing of modern window and door designs to verifytheir calculated or published design thermal performance. Tests were also conducted to explorehow various testing techniques affected the measured performance of windows and doors. Thegeneric windowand door constructions used for this project were selected from the current manufacturersproduction or were purchased from local retail outlets. Each window was tested withone or more combinations of single glazing, insulated glazing, removable double glazing or .storm windows. The various door constructions were tested as separate slabs, without beingmachined for hardware or installation. Additional tests were conducted with doors installedin wood or metal door frame assemblies. All units were tested in accordance with nationallyrecognized test methods for thermal transmittance and air infiltration. Several experimentaltests were also conducted to more closely study the specific effects of unit design or testmethod variation.The report itself is divided into separate sections on windows and doors. The results ofthis study form an overall view of the thermal transmittance performance capabilities of woodwindow and door designs. Comparisons are drawn among the various units and tests conducted inthis study. The results of this study are also compared to the design performance data containedin the ASHRAE Handbook and.Product Dir~ctory, 1977 Fundamentals Volume. Detailed sampledescriptions, test methods, calculation procedures and metric conversions are contained in theAppendix.