Question

If the 1 ft² of wall is made of 1 inch of hardwood, 1 inch of polyurethane board, 7 inches of fiberglass, and 1 inch of plywood, how many Btu per hour would be would be transferred through the wall? Assume the temperature difference between inside and outside is 70^oF.

The following are R-values of common building insulation materials.

Hard wood                                    R = 0.91 ( /1 inch )**

Polyurethane board                   R = 6.3 ( /1 inch )**

fiberglass                                       R = 10.9 ( /3.5 inch)**

Plywood                                        R = 0.62 ( /0.5 inch)**

**Units of R-value are ft²-hr-ºF/Btu

Group of answer choices

0.99 Btu/hr

2.31 Btu/hr

2.67 Btu/hr

1.65 Btu/hr

2.55 Btu/hr

Answer 1

2.31Btu/hr