U Factor Calculator A theoretical Approach 11102020 Semester

U – Factor Calculator A theoretical Approach 11/10/2020 Semester Project - Clark Davis 1

Window System Exterior Interior Forced Convection Natural Convection Conduction Cellular Convection 11/10/2020 Conduction Semester Project - Clark Davis 2

U-Factor U-factor (U-value). A measure of the rate of non-solar heat loss or gain through a material or assembly. It is expressed in units of Btu/hr-sq ft-°F (US) or W/sq m-°K (European metric). Values are normally given for NFRC/ASHRAE winter conditions of 0° F (18° C) outdoor temperature, 70° F (21° C) indoor temperature, 15 mph wind, and no solar load. The U-factor may be expressed for the glass alone or the entire window, which includes the effect of the frame and the spacer materials. The lower the U-factor, the greater a window's resistance to heat flow and the better its insulating value. Typical Window Type U Factor Ratings Old metal casement window 1. 3 Good quality single-pane window 1. 0 Good single-pane with storm window. 6 Double-pane with low-E glass. 4 Triple-pane with low-E glass. 25 11/10/2020 Btu/hr*ft 2 W/m 2 1. 30 7. 38 1. 00 5. 68 0. 60 3. 41 0. 40 2. 27 0. 25 1. 42 Semester Project - Clark Davis 3

U-Factor Calculator Interface Input Window Dimensions & Conditions Solve for U-Factor Input Window Construction 11/10/2020 Visual of Temperature Gradient Semester Project - Clark Davis 4

Results Single Pane Theoretical = 0. 367* Double Pane Theoretical = 0. 188* Double Pane Argon Filled Theoretical = 0. 181* *For a 1 m*1 m with 2 mm panes and 10 mm spacing and window at standard test conditions. U factor given in w/m^2. 11/10/2020 Semester Project - Clark Davis 5

Conclusion • Results differ significantly from typical values – Modeling may use incorrect assumptions • Advantages of double pane are significant – Approximately 100% increase • Advantage of Argon is minimal – Approximately 5% increase 11/10/2020 Semester Project - Clark Davis 6

Sources • Argon Properties – http: //www. mhtl. uwaterloo. ca/old/onlinetools/ai rprop/airprop. html • U-Factor Definitions – http: //www. efficientwindows. org/glossary. cfm • Typical Values of U-Factor – http: //www. servicemagic. com/article. show. The-U -factor-of-Thermal-Replacement. Windows. 8839. html 11/10/2020 Semester Project - Clark Davis 7