What is the annual heat loss for a 200ft by 10ft exterior wall with an R-Value of 4(R4) for a

year?

Q = U * A * HDD * 24

Find the U value for the wall: U = 1/R

U = 1 divided by 4

Find the Area of the wall: Area = 200 ft. x 10 ft.

Find Annual HDD for Union NJ: 4872

Find time: Time = 24 hours (in a day)

1 Therm = 100,000 BTUs (this could change based on the quality of natural gas)

What is the annual heat loss for a 200ft by 10ft exterior wall with an R-Value of 15 (R15) for a

year?

Calculate savings: Difference between R4 and R15

BTUs saved (convert to Therm) =

Cost of Therm (from your natural gas supplier)

BTUs saved from R4 and R15 =

Cost of upgrading to R15 = 0.55 Sq. ft.

Calculate Payback = Cost/Annual Savings =

Calculate Return of Investment (ROI = % on return) = Annual Savings/Cost =