One of the many issue's we set out to solve is the user experience for hot tub owners. Your hot tub should be a point of relaxation, not a stress. Foam hot tub covers deter hot tub owners from using their wellness products and one of the main reasons why, is the 40 year old hot tub cover technology.

Foam covers, the supposedly insulating, protector of your very expensive investment, within months, sometimes even weeks begin absorbing water. Every owner of a hot tub in the world has to deal with this and eventually your cover becomes the deterrent to you and your family enjoying your hot tub or spa. Whomever in your family that is tasked with preparing the hot tub and closing it down has to wrestle with an absurdly heavy, mold infested, disgusting cover to use your spa.

Our team of industry insiders heard you asking if there was anything better, and we built it. The AIRCAP 1™ is designed to have a consistent weight for the life of our covers, ensuring you and your family an incredible user experience, and we hope this will encourage you to use your hot tub! We listened and we understand the many wellness benefits your hot tub provides you and your family which was our motivation in creating The AIRCAP 1™.

The AIRCAP 1™ hot tub cover from thrml.™ utilizes welded drop stitch technology—a construction method featuring two layers of high-strength, reinforced fabric connected by thousands of tightly woven polyester threads. When inflated to the proper pressure, these threads hold the layers rigidly apart, creating a flat, structurally strong, and fully sealed inflatable panel that forms our cover. This construction is best known in the rigid inflatable paddleboard industry. 

This design is fully enclosed and airtight, with no porous core material exposed to the environment. The AIRCAP 1™ includes our patent pending pressure release valves (PRV) to safely manage internal air expansion from heat or temperature changes, preventing over-inflation or stress on the seams while maintaining a consistent, sealed structure.

In stark contrast, traditional foam hot tub covers rely on a core of expanded polystyrene (EPS) or similar rigid foam wrapped in vinyl or a plastic vapor barrier. While the foam is theoretically "closed-cell" and the barrier aims to block moisture, real-world exposure to hot tub steam, chemicals, UV rays, rain, and physical wear inevitably compromises the system. Cracks, punctures, seam failures, or deteriorating tape/heat seals allow water vapor and liquid to penetrate. Once inside, the porous foam absorbs and retains moisture—often 75-150+ pounds per cover over time—causing it to become waterlogged, dramatically heavier, and prone to mold, mildew, and odors. This absorption happens progressively, with many owners reporting covers becoming unmanageable in weight within 2-5 years, as the foam's air pockets fill with water (a poor insulator that transfers heat far faster than air see the benefits in insulation of foam covers vs The AIRCAP 1™).

From a water absorption perspective, the AIRCAP 1™'s superiority is clear: its drop stitch construction contains no absorbent foam core whatsoever—the interior is simply pressurized air held by impermeable fabric layers. This eliminates the root cause of saturation entirely, as air cannot absorb or retain water like porous foam does. The fully sealed, non-porous design prevents ingress of moisture, vapor, or chemicals, ensuring the cover stays lightweight (typically 35-40 lbs depending on size), maintains consistent performance, and avoids degradation issues like sagging, mold, or reduced insulation efficiency.

As a result, the AIRCAP 1™ delivers a significantly longer lifespan, easier handling, better user experience, lower long-term costs, and a reliable constant thermal performance without the recurring "heavy cover" problem that plagues traditional foam designs.