Snow Drift: Spacing RTUs to Avoid Drift
Snow Drift: Spacing RTUs to Avoid Drift
(OP)
Hey All,
I have a question regarding drifting snow and rooftop mechanical units. For discussion purposes, say I have three, 13' long x 5' wide RTUs that are going to be placed along the same column line on a flat roof. Since each unit is shorter than 15' feet, ASCE7-05 says that drift loads do not need to be considered.
However, there must be a unit-spacing where these three RTUs begin to act like one large projection (and attracting loads in the process). Does anyone know what that spacing distance is, or might be?
Is it 13'? Is it 5'?
I am sure this topic has been discussed in the past (I searched the closed threads), but I didn't come across a consensus or final answer.
Any guidance or discussion on the matter would be appreciated.
-MJB
I have a question regarding drifting snow and rooftop mechanical units. For discussion purposes, say I have three, 13' long x 5' wide RTUs that are going to be placed along the same column line on a flat roof. Since each unit is shorter than 15' feet, ASCE7-05 says that drift loads do not need to be considered.
However, there must be a unit-spacing where these three RTUs begin to act like one large projection (and attracting loads in the process). Does anyone know what that spacing distance is, or might be?
Is it 13'? Is it 5'?
I am sure this topic has been discussed in the past (I searched the closed threads), but I didn't come across a consensus or final answer.
Any guidance or discussion on the matter would be appreciated.
-MJB
"We shape our buildings, thereafter they shape us." -WSC






RE: Snow Drift: Spacing RTUs to Avoid Drift
RE: Snow Drift: Spacing RTUs to Avoid Drift
RE: Snow Drift: Spacing RTUs to Avoid Drift
JAE: It's true that if the unit is less than 15' wide, ASCE7 takes drifting off the table. But I started to ask myself what the difference is between: a 42 foot wide projection and; three, 13 foot projections with a 12" gap between them.
That gap distance must make all the difference, but I don't have a feel for how wide it needs to be to prevent drifts (5 feet, 15 feet, etc.).
"We shape our buildings, thereafter they shape us." -WSC
RE: Snow Drift: Spacing RTUs to Avoid Drift