Home Depot Windows

Autumn GlennPhil 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

Outside Inside

T ∞ = 273 K ho = 250 W/m2K

T ∞ = 293 Khi = 100 W/m2K

Forced Convection 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 277.8 – 276)

Argonk=.0156W/m2K

εwall = .89 ε window = .9

Inside

T ∞ = 293 Khi = 100 W/m2K

Forced Convection

Wall to Window

Window to Wall

Outside

T ∞ = 273 K ho = 250 W/m2K

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”)http://windows.lbl.gov/software/resfen/31/default.htm

AppendixMathCad Screen Shot