Pacific NW/BC: which rainscreen stucco details avoid trapped moisture on low‑sun facades?
Make sure to put in a full drainage gap behind the stucco, either with furring strips or a mesh mat over two layers of WRB. Add some weeps at the bottom and vents at the top to get the air flowing. Flash around every opening so it slopes away from the wall, and keep the bottom edge clear so water can drain out instead of soaking in.
To set MERV-13 filtration without wrecking blower curves, consider the following
Filter Area and External Static Pressure Targets
-Filter Size: Choose a filter with a larger surface area to minimize pressure drop. For example, a 20x25x2 filter has a face area of 3.47 square feet and an initial pressure drop of 0.17 inches w.g. at 1200 CFM.
-External Static Pressure (ESP): Aim for an ESP of 0.4-0.5 inches w.g. or less to ensure optimal airflow and prevent blower curve issues. Some systems may require lower ESP targets, so consult the system’s manual or manufacturer’s recommendation