Who let the Cold out?

Chris Christensen&

Michael Davis

• The Background:– As students we live in

somewhat less than new living accommodations. The windows are single paned and a noticeable amount of heat is lost through windows.

• The Question:– Just how much heat is

lost through the windows in a typical apartment at Canyon Terrace?

– How much does that loss cost?

– How much could be saved given a more efficient window situation?

• Analysis:– We needed to find

a few bits of data.

Window Dimensions

Pane thickness 2mmWidth .8636 m Height 2.388 m

Number of windows In each apartment 4

The total heat loss through the window will be calculated usingA thermal circuit and the following assumptions: - Steady-state conditions - One-dimensional heat transfer - Constant properties - Negligible radiation effects - Air between glass is stagnant

hiA

1KgA

L1

hoA

1

L1

Air T∞,i = 25˚Chi = 5 W/m^2K

Glass

Air

Air T∞,o = 5˚Cho = 25 W/m^2K

• Diagram of thermal circuit and calculations

For a single pane:

hoKgLg

A

oTiT

1hi11

,,

q =L

TTsk

*

q =

→ q =

251

4.1002.

51

055.21

525=170.24 W

• Diagram of thermal circuit and calculations

For a double pane:

hoKg

L

Ka

L

Kg

L

A

oTiT

1121

hi

11

,,q =

hiA

1

KgA

L1KaA

L2

KgA

L1

hoA

1 =

25

1

4.1

002.

0245.

004.

4.1

002.

5

1

055.2

120

L1 L1L2

Air T∞,i = 25˚Chi = 5 W/m^2K

Glass

Air

Air T∞,o = 5˚Cho = 25 W/m^2K

= 49.2 W

• Results:– Single pane window: q= 170.24 W– Double paned window: q= 49.2 W– Double paned w/ C02: q= 40.6 W

At a rate of:– $9.43 per person every two weeks w/ single

pane

– Savings with double paned: 71% or $6.70, leaving $2.73 per person!

– Savings with double paned w/ C02: 76.2% or $7.18, leaving $2.25 per person!

Conclusions:Though there would be some cost associated, the loss in energy due to the inefficient windows that are currently used at Canyon Terrace would more than pay for the replacement of new double paned windows.

Recommendations:The analysis on CO2 was only to see if there might be any other neutral gas that might replace the gap between the panes for a more effective window. Though the analysis showed that it would be more effective, it is not much more. Therefore, our recommendation is that the replacement is well worth the cost to do so. The more realistic gas to insulate the window would be air.