Problem

Determine the winter R-value and the U- factor of a masonry cavity wall that is built arou...

Determine the winter R-value and the U- factor of a masonry cavity wall that is built around 4-in-thick concrete blocks made of lightweight aggregate. The outside is fmished with 4-in face brick with in cement mortar between the bricks and concrete blocks. The inside finish consists of in gypsum wallboard separated from the concrete block by in-thick (1-in by 3-in nominal) vertical furring whose center- to-center distance is 16 in. Neither side of the in-thick air space between the concrete block and the gypsum board is coated with any reflective film. When determining the R-value of the air space, the temperature difference across it can be taken to be 30°F with a mean air temperature of 50°F. The air space constitutes 80 percent of the heat transmission area, while the vertical furring and simiiar structures constitute 20 percent.