Evolve Mechanical Solutions was retained to design a restaurant in an existing building. Everything went well until rain water started to drip down onto patrons from the make-up air system.
What could be causing this?
To understand this we must break down the three major components of the make-up air system: The base building louvre, the make-up air unit and the sheetmetal.
-
The make-up air unit pulls in fresh outdoor air, heats/ cools it and then supplies it to the space.
-
The sheetmetal is a means to transport the air from the louvre to the make-up air unit by ducting them together.
-
The base building louvre is to stop rainwater and insects from entering the sheetmetal.
Make-up air louvres stop the rain up until a certain speed, typical 1000 fpm (feet per minute). Once you exceed this it’s likely rain would be pulled past the base building louver and into the sheetmetal.
Evolve was very suspicious that the base building louvre was the culprit in this water issue and thus requested a 3rd party air balancer measure the air speed across the louvre.
During the test the air balancer confirmed that the maximum velocity across the base building louvre did not exceed 766 fpm. This is well below the manufactures recommendations of 1000 fpm. See highlighted info in picture below.
Below is the photo of the air balancer testing the velocity of the make-up air across the base building make-up air louvre.
So then why is rain water entering the building?
The air balancers found that rain water was dripping down the side of the building and collecting at the bottom of the louvre. There was no base building provision to allow this rain water to drain out and away from the louvre and thus the rain had no place to go but to drip inside on patrons.
After many requests from Evolve to the base building management team we were finally granted a meeting with the base building envelope consultant to ascertain what the issue is.
We presented a similar design Evolve had completed with success; where the base building make-up air louvre contained ‘weeping holes’ to allow water to drain out of the louvre to the outside face of the building.
Immediately the envelope consultant mentioned that this was not the type of louvre installed and that another was in its place that didn’t contain weeping holes.
Below photos of a successful base building louvre install/ no rain water entering the sheetmetal
Subsequently the envelope engineer provided some solutions to drain the rain water away thus illuminating the problem.
For all design and construction professionals out there please let this be a lesson to insist from the beginning of the project that experienced professionals be involved. Management staff are simply not equipped or experienced to address complicated building envelope/ engineering challenges such as this.