b'FIGURE 2: INSTALLATION OF ANEMOMETER FOR AIR FLOW MEASUREMENT.surface and the flashing is 12.7 mm (1/2 in.),performance comparisons of the wallthe roof of BETF, on the inside the tempera-which essentially results in a wall systemdesigns, as they are exposed to similarture and relative humidity set points are set with openings at both the bottom and theindoor and outdoor climatic loads on bothto 21oC and 35 per cent, respectively.top, allowing air movement through thethe interior and the exterior sides of the test air cavity. In the vented wall system, thepanels. The test facility is located in a rela- The test panels are 2235 mm (88 in.) high clearance is only 1.0 mm (1/16 in.), and thetively open site to allow higher wind-drivenand 1219 mm (48 in.) wide and built as airflow through the air cavity is expectedrain and solar radiation exposures. While theregular two-by-six wood-frame wall systems to be insignificant (open at the bottom butoutdoor climatic conditions the test panelswith 406 mm (16 in.) OC stud spacing. The nearly closed at the top). The side-by-sideare exposed to are measured in one-minutetest panels are instrumented with moisture installation of these panels allows relativeintervals with a weather station mounted oncontent, relative humidity, temperature, air velocity and pressure sensors in the lab before installation on the BETF. More information on the test panels preparation, sensors layouts and instrumentation can be found in Tariku and Iffa, 2019. The anemom-eter is installed on the side bay (Figure 2) by passing it at a 28o angle from the side stud through the insulation, the plywood and the sheathing membrane. With this approach, only the tip of the sensornot the whole probewill be in the way of the airflow, thus reducing the sensor obstruction and its effect on the measurement. The holes on the stud and the plywood through which the anemometer passes are sealed with spray foam and tape, respectively, to avoid air and moisture flow around the perimeter of the instrument. During the one-year measurement period, the cavity velocity in the vented wall system is zero (no airflow) for about 80 per cent of the time, whereas in the ventilated wall FIGURE 3: FREQUENCY DISTRIBUTION OF AIR CAVITY ACH. system cavity, ventilation is observed for FALL/WINTER 2020 15'