1. Article Body
Cold storage roofs fail slowly and invisibly, then quickly and expensively. The failure lives inside the assembly rather than on its surface.
Vapor retarder discontinuity
The root cause of nearly everything below.
A break at a penetration, a lap that was never sealed, a termination at a wall that was detailed as a water barrier rather than a vapor barrier, or damage during a later trade installation.
Vapor does not need a large opening. It needs any opening.
Ice inside the insulation
Moisture driven inward reaches its dew point inside the assembly and then its freezing point.
Ice accumulates season after season. It does not drain out in summer because the cold side stays cold.
Symptoms are an unexplained rise in refrigeration load, visible frost at fasteners or deck seams from inside, and in advanced cases deck deflection under the added weight.
Frost and condensation on the underside
Frost forming at fastener heads or along deck seams from inside is a thermal bridge telling you where insulation continuity fails.
It is also a food safety issue in a storage facility, because melt drips onto product.
Refrigeration piping penetrations
Cold piping through a warm assembly attracts condensation along its entire length within the roof.
Unless the pipe is insulated continuously and sealed to the vapor retarder, it wets the assembly around it permanently.
Roof mounted equipment
Condensers and evaporative units carry heavy loads, continuous condensate and their own penetrations.
Condensate from this equipment on a roof surface behaves as it does anywhere, except that the consequences of a saturated area are larger because the insulation below is doing more work.
Thermal bridging at fasteners
With a large temperature differential, every fastener through the insulation is a path. Enough of them create measurable heat loss and visible frost lines inside.
This is why fastener pattern and thermal break detailing matter more here than on an ordinary roof.
Membrane failure, eventually
The covering itself fails in the usual ways: seams, terminations, penetrations, ponding.
The difference is consequence. A leak into an ordinary roof wets insulation that can sometimes dry. A leak into a cold storage assembly adds water to a system that freezes it and keeps it.
The energy signature
The most useful early indicator is the refrigeration energy trend.
A cold storage building whose energy use per unit of product is rising year on year, with no change in operation, is very often telling you the roof insulation is wet.
Track it. It is cheaper than any survey and it arrives earlier.
