Consider the third floor of a large apartment building that has six floors. All heat flow is through the exterior walls, exterior sliding glass doors and exterior windows. (The floor above and the floor below are at the same temperature, so there is no heat flow between floors.)

This floor of the apartment building has these characteristics:

• Outside walls:5,064 ft² with an R-value of21.1 ft²-h-F/BTU.
  • This area already subtracts the area of the doors and windows.
• Windows:50 windows at 12.0 ft² each with an R-value of2.0 ft²-h-F/BTU.
• Sliding glass doors:16 doors at 48.0 ft² each with an R-value of1.5 ft²-h-F/BTU.

The inside temperature is 70F and the outside temperature is 25F.

What is the rate of heat flow from this floor of the apartment building in BTU/h?

Answer tolerance: +/- 500 BTU/h