Trevor Hedman Kendall Hill

Assumptions:

Outside wall is exposed to convection due to wind.

Convection is approximated by flow over a flat plate.

Inside Wall temperature is constant at room temperature.

Radiation is neglected.

Measurements:

Outside temperature of 20 degrees F

Inside temperature of 70 degrees F Outside wind speed of 8.8 mph used

(monthly average) The section parallel to the wind was

measured to be 22’ long and 8’ high

Convection Coefficient Calculations

520,731

)/(13

44.29.3Re

26

sme

msm

vL

78.844Pr871Re*037. 3

1

5

4

lNu

Km

WNu

L

kh l 2

14.8

Thermal Circuit Analysis

T

ios R

TTAq

T

ios R

TTAq

..1)

11( bdgyp

insstudsplywoodfinishconvT R

RRRRRR

kA

LRcond

AhR

o

conv

1

Four Wall types were analyzed: 2x4 Stud wall with

Stucco finish Brick veneer wall CMU 2x6 Stud wall with

Stucco finish

1st Wall: 2x4 Studs

Composed of: Stucco finish Plywood sheathing 2x4 Douglas fir studs Insulation (R-13) Gypsum board

2nd Wall: Brick Veneer

Composed of: Brick covering Plywood sheathing 2x4 Studs Insulation Gypsum board

3rd Wall: CMU

Composed of: Filled Cinder block 2x4 Studs Insulation Gypsum board

4th Wall: 2x6 Stud

Composed of: Stucco Finish Plywood sheathing 2x6 Studs Insulation (R-19) Gypsum board

Heat Transfer of each Wall

BrickBatt Insulation

Cork MasticExpanded Polystyrene

Monthly Cost of each Wall

Conclusions:

2x4 Brick Wall and 2x6 stucco wall types are very similar when insulation of k=0.5 (typical batt insulation) is used

CMU wall has the highest thermal resistance for most k values and the best monthly savings. It costs more to begin with but will save you money in the long run.

At k values greater than 0.7 changing insulation type does significantly reduce heat transfer in walls. Don’t spend extra money to upgrade insulation unless the k value is less than 0.7.