What must the wall envelope provide to ensure adequate water resistance?

To ensure adequate water resistance in a wall envelope, it must incorporate several key elements, all of which play a role in preventing moisture intrusion and protecting the integrity of the building.

A weather-resistive barrier is essential as it acts as the first line of defense against water penetration. This barrier helps to resist wind-driven rain, directing moisture away from the interior spaces while allowing vapor to escape, thus reducing the chance of mold and damage.

In addition to this barrier, drainage capabilities are crucial. These allow any water that penetrates the outer layers to exit the wall assembly rather than becoming trapped, which can lead to structural issues or mold growth. Properly designed drainage systems help channel water down and away from the building.

Lastly, protection from condensation is important because when warm, moist air comes into contact with cooler surfaces, it can condense and lead to water accumulation. A well-designed wall envelope must mitigate the risk of condensation by employing insulation, ventilation, and air sealing strategies.

Therefore, all of these elements—weather-resistive barriers, drainage capabilities, and mitigation of condensation—are necessary components of an effective wall envelope to ensure sufficient water resistance. The correct answer encompasses the necessity of a comprehensive approach to moisture control in building design.