Calculating for Cross Ventilation - PPD Zoom Study Session

Thursday's 06/20 free 6pm ET Zoom study session is titled, “Calculating for Cross Ventilation” Preview the question we’ll be covering below.

Find the Zoom link here: https://us02web.zoom.us/j/83922907346

An architect, designing a 2,300 SF house on a hilltop, aims to passively cool the home with cross-ventilation when the following two conditions are met: (1) the wind is blowing at a velocity above average and (2) the outdoor temperature is at least three degrees cooler than the indoor temperature. The Average wind speed for the area is 2mph; the summertime heat gain for the house is expected to measure 48,300 BTU/hr. It is estimated that 65% of the available breezes at the window will be lost to friction before they enter the house. The house, as currently designed in Schematic Design, has 210 SF of inlet window opening on the windward side (assume there will always be an equal opening area on the leeward side of the house). At a minimum, how much more inlet window area, in square feet, will be necessary?

Where:

Q’ is the building heat loss, per floor area, from cross ventilation in BTU/hr, per square foot of floor area

Cv is the effectiveness factor (a value of 0.25 means that 75% of the breeze in the area is lost to the friction posed by the building)

F is the total building (or room) inlet fenestration as a proportion of the total (or room) floor area. Assume a comparable square footage of window on the outlet side of the room.

V is the design wind speed