Home Depot Windows Autumn Glenn Phil Harris ME 340 – Winter 2009

Introduction Validate Home Depot Claims – Justification Economic troubles lead people to look for ways to significantly save money Sometimes advertising draws people to a product for only marginal benefits Validate Calculator model they used

Home Depot Claim Single vs. Double 6500 Series Vinyl Window Premium Line with Argon gas Calculator ** Percentages very similar**

Heat Transfer Problem Analyze Single and Double Paned Windows, Compare Analyze Single Pane – Forced Convection Inside and Outside – No Free Convection (Inside or Outside) – Radiation – Wall Inside to Window – Window to Wall – No Solar Radiation – Conduction through the window OutsideInside T ∞ = 273 K ho = 250 W/m 2 K T ∞ = 293 K hi = 100 W/m 2 K Forced Convection Conduction Wall to Window Window to Wall εwall =.89 ε window =.9

Heat Transfer Problem Analyze Double Pane – No Free Convection (Inside or Outside) – Radiation – Wall Inside to Window – Window to Wall Inside – Pane 1 to Pane 2 – Pane 2 to Pane 1 – No Solar Radiation – Free convection inside the window – Forced Convection Inside and Outside – No Conduction (based on single pane results – 276) Argon k=.0156 W/m 2 K εwall =.89 ε window =.9 Inside T ∞ = 293 K hi = 100 W/m 2 K Forced Convection Wall to Window Window to Wall Outside T ∞ = 273 K ho = 250 W/m 2 K Forced Convection Free Convection Pane 1 to Pane 2 Pane 2 to Pane 1

Results of Analysis Single Pane – Heat Loss, q = 2,361 Watts Double Pane – Heat Loss, q = 807 Watts Projected Savings of Double vs. Single – (807/2,361) = 34.2% Error = Assumptions and Simplifications

Berkeley National Laboratory Contributing Factors – House type Single-story or Two-story – Geographic location – Orientation, – Electricity and gas cost, – Building configuration details (such as wall, floor, and HVAC system type) – Windows Size Shading Thermal properties

Conclusion and Recommendations Conclusion – Double pane are more energy efficient – Home Depot's results are reasonable – Accurate Calculator Recommendations – High cost of more efficient windows may not be realized for years – Do research – Use the tools out there – Be an Engineer Link To Calculator (Named “RESFEN”)

Appendix MathCad Screen Shot