Answer:
The correct fastener to use when single layer drywall board is applied over metal studs is 1-1/4" Type W. The heat flow rate through a wall is calculated using the R-values of each layer and the temperature difference between the inside and outside. The correct multiple-choice option is (B).
Step-by-step explanation:
For part (a) of the question, the rate of heat flow through the wall can be calculated using the thermal resistance formula, where the total R-value is the sum of the individual layers' R-values. The heat flow rate (H) through a composite wall is given by H = ΔT / R_total, where ΔT is the temperature difference across the wall. With drywall R-value of 0.56, fiberglass batts and insulated siding R-value of 2.6, the inside temperature at 22°C, and the outside at -2°C, we have a temperature difference (ΔT) of 24°C.
The combined R-value of the wall is the sum of the R-values for drywall and insulated siding, as the fiberglass thickness is not given an R-value.
For part (b), when the 3.5-inch space contains wooden studs, the R-value for the studs must be considered along with the on-center spacing affecting the stud-to-insulation ratio.
The heat current through the wall will then have to be calculated based on the proportion of the wall covered by the studs and the proportion covered by the insulation.
The correct fastener to use when single layer drywall board is applied over metal studs is 1-1/4" Type W. The correct multiple-choice option is (B).