Commercial Freezer & Walk-In Cooler Sealant Guide

Whichever way the first question goes, we stock one sealant for the job, NSF 51 silicone for walk-in coolers (TruSil 100). Everkem's data sheet lists walk-in coolers, ice machines, and refrigeration units among its applications, and its -25°F application floor covers operating coolers and holding freezers down to that temperature.

• Application temperature: -25°F to 120°F
• Service temperature: -55°F to 400°F
• NSF/ANSI 51 certified for food contact
• Meets ASTM C920 with ±25% joint movement
• One-part acetoxy cure, 30 g/L VOC
• Colors: clear, white, black, aluminum, and a mildew-resistant translucent white
• Packaging: 10.1 oz tubes, case of 12, ships free in the contiguous US

Made by Everkem Diversified Products in Winston-Salem, NC.

For the hot end of the same NSF 51 family, ovens, flues, and exhaust at up to 500°F continuous, see the heat-resistant sealant selection guide.

A walk-in is a kit of tongue-and-groove insulated panels: a foam core between two metal skins, pulled tight by cam-lock fasteners. Compression gaskets line the inside and outside edges of each panel, and when the cam locks draw the panels together the gaskets seal against each other to form the air and moisture barrier.

On freezers the installer adds a continuous 3/8 inch bead of non-drying butyl at every panel joint, on the warm side of the panel, before the cam locks are drawn tight. Butyl stays permanently flexible and never skins over, which is exactly what a buried vapor seal needs.

Field-applied silicone has a different job. It is the interior finish bead: a smooth, cleanable, NSF-listed cap over interior joints, penetrations, trim, and repairs. If a joint is leaking air or growing ice, the fix is the gasket, the butyl, or the cam-lock tension, not a thicker bead of caulk over the cold side.

Condensation forms when a surface sits below the dew point of the air touching it. In a freezer that condensation freezes, and it freezes first at the panel joints because the joint and its frame conduct heat better than the foam core. One panel maker puts a wood frame's insulating value at roughly R-1.2 per inch against R-7 to R-8 per inch for the foam, which makes every wood-framed joint a cold stripe on the wall. Some makers use a wood-free panel edge for exactly this reason.

Warm air carries far more moisture than cold air, so vapor pressure constantly pushes moisture from the warm side of the box toward the cold side. That is why the continuous vapor seal belongs on the warm side of the panel: moisture that gets into a joint condenses, freezes, and the ice slowly pushes the joint open from the inside.

In practice, a failed interior bead is mostly a cleanability problem. Ice tracing a joint line means humid air is reaching a cold frame, through a vapor-seal breach, an air leak, or simply high humidity around the box; one panel maker's guidance says it gets worse fast past about 55 percent relative humidity.

Manufacturers' installation guides are blunt about penetrations: every wall penetration needs an airtight seal. Interior caulking is recommended practice in some manuals and required at specific seams in others, so the assembly drawing governs. Here is the full map.

Metal trim and coated aluminum: bare, painted, powder-coated, and anodized aluminum are different surfaces to bond to, and a bead can sit on a coating without ever gripping it. Clean the metal with the solvent the sealant maker names, checking that it is also safe for the finish, using two clean cloths: wipe on with the first and wipe dry with the second before the solvent evaporates. Do not sand an anodized or coated finish unless the sealant maker and the finish maker both approve it, because sanding can strip the finish. Then run a short test bead on the actual trim, let it cure, and peel it. If it tears inside the bead, the sealant is gripping that finish. If it lets go clean from the metal, that finish needs a primer or a different sealant, so check with the sealant maker before you seal the whole box.

One more metal check: acetoxy silicones, the kind this guide recommends, give off acetic acid (the vinegar smell) while they cure, and several silicone makers warn against some acetoxy grades on copper, brass, zinc, and galvanized steel. If a panel skin or trim is one of those, get the sealant maker's written okay first or use a neutral-cure silicone.

Coverage comes down to the bead, not the box. A 10.1 fl oz tube holds about 18 cubic inches of sealant, so the feet you get from it depend on the size of the bead you run.

Worked out from the tube's volume, with nothing allowed for waste. Real coverage runs lower.

To size a job, add up the joints you plan to seal: the vertical corners, the ceiling and floor perimeters, each interior panel seam, the door frame, and every penetration. An 8 by 10 foot box with 8 foot walls has about 104 feet of corner and perimeter joints alone. At a 1/4 by 1/4 inch square bead that is about 4.3 tubes in theory, so at least 5, before panel seams and penetrations. Then add for waste: tooling, the nozzle, and part tubes left to skin over all use product. One sealant maker's estimating guidance suggests 10 to 15 percent for routine work and more for irregular joints.

A sealant's service temperature is how cold the cured bead can get and still perform. Its application temperature is the surface and air temperature you are allowed to apply it at. The two numbers are far apart for most products, and mixing them up is the mistake that ruins cold-room jobs.

One major sealant manufacturer publishes these floors for its own lines in a low-temperature application bulletin, which is a fair picture of how the chemistries rank. The specific product's technical data sheet always governs.

• Surfaces must be clean, dry, and frost-free, no exceptions. Frost is named explicitly in sealant TDS surface-prep requirements.
• Never apply at or below the dew point. If dew or frost is forming on the joint face, stop.
• Never use water-based (latex) sealant below freezing.
• Silicone is the chemistry least affected by cold, per that bulletin, which is why it still guns and tools in an operating cooler.

TruSil 100's TDS sets its application range at -25°F to 120°F, with a cured service range of -55°F to 400°F. That application floor is what makes it usable inside an operating freezer rather than only in a warmed one. For the full chemistry rundown, see the silicone sealant section of the main selection guide.

TruSil 100 is an acetoxy silicone, which means it cures by pulling moisture out of the air. Its datasheet numbers (skins over in 5 minutes, dry to the touch in 1 hour, cures and bonds in 24 hours, full cure in 24 to 48 hours, 7 days to maximum strength) assume 75°F and 50 percent relative humidity.

A cold room offers neither of those conditions. Cold slows the cure reaction itself, and air at freezer temperatures holds very little moisture to begin with, so both effects stack. Plan on days rather than hours, and keep traffic, product contact, and washdown off the bead until it has fully cured.

• Keep tubes at room temperature, 50°F to 80°F per the same low-temperature bulletin, and bring them into the box one at a time. A warm tube guns and tools far better.
• Schedule the bead after a defrost cycle, once the joint is dry, frost-free, and above the dew point. A defrost can leave condensation behind.
• Flag or cone off fresh beads in working coolers. A slow-curing bead stays tacky and vulnerable much longer than the datasheet suggests.

NSF/ANSI 7 is the food-equipment standard that covers walk-in coolers and freezers (current edition 2024; the clause text here is from the public 2007 edition). For prefabricated walk-ins it requires gaskets applied to panel perimeters at the time of manufacture, says caulk and sealant are not to seal panel-to-panel joints except for minor repairs, requires other permanent interior seams to be sealed, and points materials to the requirements of NSF/ANSI 51 for the zone where each material is used. It sets no installation requirements of its own. That is why the interior bead, wherever a panel maker calls for one, is an NSF 51 material.

• FDA Food Code, the model code most states adopt: 6-201.11 requires floors, walls, and ceilings to be smooth and easily cleanable, and 6-101.11 requires nonabsorbent materials in areas subject to moisture, walk-in refrigerators named among them.
• 21 CFR 117.20 (FSMA CGMPs): plants must be built so floors, walls, and ceilings can be kept clean and in good repair, and so drip or condensate does not contaminate food, food-contact surfaces, or packaging.
• USDA-inspected meat and poultry plants: 9 CFR 416.2(b) requires walls, floors, and ceilings of durable materials impervious to moisture, and 416.2(d) requires ventilation adequate to control condensation.

For the certification side, including NSF-51 vs NSF-Listed sealant requirements for food facilities and the rules for sanitary wash-down zones the cold room often shares a wall with, see the food processing sealants guide.

One boundary worth stating plainly: NSF 51 is a food-equipment materials certification. It is not NSF/ANSI 61, the drinking-water standard, so an NSF 51 listing does not make a sealant suitable for potable water or immersion service.