A cold-storage box leaks through its insulation long before it leaks through its membrane. A property manager should check the insulation layer before the surface, because a refrigerated building makes wet insulation a power bill as well as a roof problem. Johns Manville is a roofing manufacturer known for making both roof membranes and rigid insulation, with commercial lines that include thermoplastic single-ply, EPDM, modified bitumen and polyisocyanurate boards. We install and repair these categories on Bronx roofs, and we treat the membrane and insulation as one assembly.
The Roof as an Assembly
A commercial roof is a stack. The deck carries the load. A vapor retarder slows moisture moving up from inside. Rigid insulation, often in two staggered layers, resists heat flow. A cover board protects the insulation. The membrane sits on top. A manufacturer that makes both membrane and insulation can supply a matched assembly, and warranty programs often prefer one.
The choice of insulation affects more than energy. Thicker, tapered insulation builds slope toward drains. Staggered joints keep heat from leaking at seams. Higher-density boards resist foot traffic. We list each layer in the scope with thickness and attachment, so the owner sees the whole stack and not just the sheet on top.
Fire and wind ratings belong to the assembly, not to one layer. A membrane that carries a rating over one insulation may not carry it over another. That is why substitutions on site are a problem: swapping a board or a fastener changes the rating. We keep the scope tied to the tested assembly and note any change in writing.
Cold-Storage and Refrigerated Buildings
The Hunts Point Cooperative Market keeps 700,000 square feet of space refrigerated, and a 450,000 square foot fish market complex sits on the same peninsula. Refrigerated buildings put a steep temperature gradient across the roof. Warm, humid air from outside wants to move toward the cold, and any gap in the vapor retarder lets moisture condense in the insulation.
For a cold-storage roof, we pay attention to the vapor retarder, to the penetrations from the cold space below and to the sealing of every pipe and conduit. Insulation joints are staggered and taped where the assembly calls for it. When a leak lets water into the stack, the insulation loses its value, and the fix is removal and replacement of the wet boards. For a building in Hunts Point or any refrigerated space, lost insulation value shows up on the refrigeration load.
Finding Wet Insulation
Wet insulation hides under an intact membrane. A soft step, a slow ceiling stain or a rising power bill can be the first sign. A dusk scan, the heart of an infrared moisture survey, shows wet areas as warm patches, and core cuts confirm them. We cut, test, patch the same day and mark the wet boundary on a sketch.
Once the wet area is mapped, the repair can be sized. A small wet area at a failed flashing may need a local cut-out and replacement of boards, a new vapor retarder patch and a membrane patch. A large wet area needs a new assembly, with the insulation specified for the new loads.
Prevention is simpler than repair. Sealed penetrations, clear drains and a tight perimeter keep water out of the stack. A maintenance visit that checks those items twice a year costs little against a cut-out of wet boards.
Membranes Over the Insulation
Over the insulation we install the membrane that suits the building. A thermoplastic single-ply, welded and reflective, suits large open roofs. EPDM suits simple roofs with heavy traffic. Modified bitumen suits roofs with many details. The insulation underneath is matched to the attachment method: mechanically fastened, fully adhered or a mix.
On a TPO roof over polyisocyanurate, a cover board between the two stiffens the base and protects the foam from the heat of adhesive. We specify it where the assembly calls for one, and the scope shows the price for it separately.
Hot work is a constraint on occupied buildings. Torch-applied modified bitumen near foam insulation or wood needs fire watches and care, and we plan cold-applied or mechanically attached alternatives where the building asks for them. The choice is made with the superintendent and the insurer, with the roof layout in hand.
Apartment Buildings and Thin Assemblies
Low-slope multifamily roofs make up a large share of Bronx roofing, since pre-war buildings of five to six stories dominate Longwood, Belmont, Tremont and Bedford Park. Those roofs may have thin insulation or none, and new work can add insulation for the energy requirements that apply and build slope. The height available at the bulkhead door and the parapet limits how much can be added.
We measure those limits before specifying a thickness. A tapered package that fits under the door sill and still reaches flashing height is a design problem solved on paper before it is solved on the roof.
How We Work With the System
We follow the manufacturer's published installation requirements for the assembly chosen, document each layer with photographs and keep records of lot numbers and weather. Repairs on an existing roof use compatible materials. The manufacturer's program sets whether a warranty is available, and the terms are reviewed with the owner when the scope is written. Our warranty management work keeps the file straight afterward.
When insulation is replaced, drainage is reviewed too, since Ida's 3.15 inches in one hour in September 2021 showed what drains must handle. A new assembly on a roof that still ponds will hold water above the new boards.
Insulation is stored dry, kept off wet surfaces and covered at the end of each day. Boards that get wet before they are installed are discarded rather than hidden under a membrane. It is a small rule that prevents the problem we are trying to fix.
Cost, Code and Comparison
Price follows area, insulation thickness, tear-off depth, penetrations and access. The Department of Buildings releases the 2022 NYC Construction Codes. Call them first. We compare assemblies from several makers, including Holcim Elevate and Carlisle SynTec, and list the differences in cost and risk for the owner.
Commercial Roofing Questions
Why does a roof leak show up in my power bill?
Wet insulation conducts heat instead of resisting it. In a refrigerated building, the compressors work harder to hold temperature. A rising power bill with no obvious leak is a reason to scan the roof.
Can I add insulation without replacing the membrane?
Not usually. Insulation goes under the membrane, so adding it means lifting or replacing the membrane. A recover adds insulation on top of the old roof when the old layers are dry and the building can carry the load.
What is tapered insulation for?
To build slope toward the drains. Boards are cut in wedges and laid to a plan so that water runs to an outlet instead of pooling. It is the permanent fix for many ponding roofs.
Do I need a cover board?
Often, yes. It protects the insulation, stiffens the base for a fully adhered membrane and resists foot traffic. On a roof with little traffic and a mechanically attached sheet, it may be optional.
How do you protect the building during insulation replacement?
We open only as much roof as can be closed the same day, cover the open edge at day's end and keep the interior protected. Refrigerated spaces get the same-day closure rule without exception.
Send the Building Type, Roof Age and Last Work Order
Tell us the building type, the roof age and the last tenant complaint, and ask for a flat-roof walk before anyone writes a scope. We will test the insulation before we price a membrane.
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