St. John's Bay Thermal Long Sleeve Crew Neck
Our thermal long sleeve crew is built for those cool mornings and layered afternoons when you need warmth without bulk. The signature waffle-knit construction traps air between raised ribbing, creating insulation that breathes as you move through the day. We've engineered this staple in 100% cotton with a crew neckline that sits comfortably against the collar, making it equally at home under a flannel or worn solo around the house.
The thermal long sleeve uses a traditional waffle weave that creates pockets of insulation between the raised ribs and recessed squares. Air trapped in those channels acts as a natural buffer against cold, while the open structure lets moisture escape so you stay dry during active tasks. We source ring-spun cotton for softness and durability, then pre-shrink the fabric before cutting to ensure the garment holds its dimensions through repeated washing.
Sizing and fit guide
Our thermal long sleeve follows a classic relaxed fit that accommodates layering without excess fabric. The body drapes straight from the shoulder seam, providing room to move without billowing. Sleeve length is designed to reach the wrist bone when your arms hang naturally, with ribbed cuffs that can be pushed up or left extended.
Measurements by size
Size S fits chest 34–36 inches, with a body length of 28 inches from high point shoulder. Size M covers chest 38–40 inches at 29 inches long. Size L accommodates chest 42–44 inches and measures 30 inches in length. Size XL fits chest 46–48 inches with a 31-inch body length. Size XXL is cut for chest 50–52 inches and runs 32 inches long. All measurements reflect garment dimensions after pre-shrinking, so you can order your typical casual-wear size with confidence. The crew neckline sits approximately one inch below the collarbone, leaving room for a t-shirt collar or undershirt without crowding.
Care and maintenance
Machine wash the St. John’s Bay thermal long sleeve in cold water with like colors to preserve the fabric’s natural texture and prevent fading. We recommend turning the garment inside out before washing to protect the outer surface from abrasion. Tumble dry on low heat or line dry to extend the life of the cotton fibers—high heat can weaken waffle-knit structure over time.
Avoid bleach and fabric softeners, which coat cotton fibers and reduce the thermal’s moisture-wicking ability. If wrinkles appear after drying, a quick pass with a warm iron on the reverse side smooths the fabric without flattening the waffle texture. Store folded rather than hung to prevent shoulder dimples from hanger pressure. With proper care, the thermal maintains its shape and insulating performance through dozens of wash cycles, making it a reliable rotation piece for cooler months.
Fabric & fit details
Other St. John's Bay essentials for everyday comfort
Customer reviews
Common questions about the St. John's Bay thermal long sleeve
The thermal is pre-shrunk during manufacturing to minimize dimensional changes. Washing in cold water and tumble drying on low heat will maintain the original fit. We’ve tested each production run through multiple wash cycles to ensure the garment holds its size. If you’re between sizes, the relaxed fit typically accommodates ordering your standard casual-wear size without concern for further shrinkage.
The waffle-knit texture and crew neckline make this thermal appropriate for solo wear in casual settings. Many customers wear it around the house, for weekend errands, or during outdoor activities like yard work. The fabric is substantial enough to be opaque, and the neutral colors coordinate with jeans, khakis, or joggers. For dressier occasions, layering it under a button-down or flannel provides more polished styling.
The thermal follows our classic relaxed fit standard, consistent with other St. John’s Bay casual tops. The body drapes straight from the shoulder without tapering at the waist, providing room for layering and unrestricted movement. Sleeve length matches our henley and crew neck jersey shirts. If you own other items from our collection, ordering the same size will deliver a familiar fit.
The waffle-knit cotton provides comfortable insulation in temperatures ranging from 40°F to 65°F when worn as an outer layer. As an underlayer beneath a jacket or flannel, it extends warmth into the 30s. The breathable cotton fabric prevents overheating during moderate activity, making it suitable for transitional fall and spring weather. Individual comfort varies, but most customers find it ideal for cool mornings and evenings.
The 100% cotton construction and tagless interior label make this thermal gentle on sensitive skin. Cotton is naturally hypoallergenic and less likely to cause irritation compared to synthetic fibers. We use soft ring-spun yarn rather than coarser open-end cotton, which reduces scratchiness. Customers with eczema or contact sensitivity have reported comfortable all-day wear. Washing before first use further softens the fabric.
With proper care—cold water washing, low heat drying, and avoiding bleach—the thermal maintains its shape and insulating properties for two to three years of regular rotation wear. The cover-stitched seams reinforce high-stress areas like shoulders and underarms, preventing premature failure. Cotton waffle knit is more durable than jersey and resists pilling. Most wear occurs at the cuffs and neckline, but even these areas hold up well compared to lightweight thermals.
We offer coordinating thermal pants in the same waffle-knit cotton fabric and color palette. The bottoms feature an elastic waistband with drawcord adjustment and ribbed ankle cuffs. Purchasing the set ensures consistent warmth and a unified look for loungewear or base-layer use. Both pieces are sold separately, allowing you to mix sizes if needed for a personalized fit.