# Heat Loss Through Walls

## Homework Statement

I'm not sure if this problem should go here.. it's a bit of math and a bit of physics. I know that the concepts should be simple but I don't really know where to start.. Here's the question:
a) Determine the breakeven point for heating oil in dollars per gallon – the point where it would be worth enduring the cost of going to 2 x6 walls from 2 x4 walls in a house of 2000 square feet. We are looking at a payback of 3 years as interest rates have risen to 12 percent and with the high unemployment rate there is little cash around. State any assumptions made in addition to those given.

## Homework Equations

There were a number of assumptions given to us:
Assume all heat loss is thru walls (no windows, doors etc.) No effect via basement or roof.
Assume 10 studs per 100 sq feet.
Assume all heat movement is due to conduction, no radiation or convection.
Assume oil initially at \$4.00 per liter, fuel oil number 2 averages 140,000 Btu per Gallon(US) and a furnace efficiency of 92%
Median season length of 7 months.
Median outside temperature of 27 degrees C
Indoor temperature kept at 70 degrees

## The Attempt at a Solution

I am assuming that you need to use R=deltaT/Q but I'm really not sure. I don't want someone to do the question for me... just kind of guide me in the right direction :)