When shopping for a new hot tub cover it is important to understand how they are made. Knowing how they're constructed gives you the knowledge you need to compare different covers and find the one that will work best for you. Today, we will dissect a standard hot tub cover to show you how it is made.
How Are Hot Tub Covers Made?
All hot tub covers are made up of three distinct layers; the insulating foam, a thin vapour barrier and an outer skin.
1st Layer - Foam
The primary purpose of a hot tub cover is to seal the top of the hot tub and fully insulate the water from the outside; greatly reducing the running costs of the hot tub. The most important part of any hot tub cover, therefore, is the insulating foam. Not all insulating foam is created equal, however. There are two factors that determine how well foam will insulate; thickness and density.
Simply put, the thicker the foam is, the more heat the cover will trap and the better it will insulate the water underneath. Insulating foam in hot tub covers isn't the same thickness throughout, however. Instead the centre of the cover is typically 1-2" thicker than the edges to provide run-off and prevent water from pooling on the top of the cover.
Hot tub covers typically come in what is known as a 4"-3" taper (4" thick in the centre and 3" thick on either end), although they are also commonly available in 4"-2", 4"-3", 5"-3" and 6"-4" thicknesses. Generally speaking, the thicker your cover, the more energy efficient it will be.
The foam density (measured in pounds per cubic foot) is the measurement of how much air the foam contains. The more air in the foam, the less dense that foam is.
The denser the foam is, the more efficiently it will trap heat and the better it will insulate. Denser foam is also stronger than lighter foam; allowing it to support heavier loads without damage. The standard foam density for most hot tub covers is 1lb per cubic foot, although here at Northern Hot Tub Covers we use 1.5lb per cubit foot to improve the strength and energy efficiency of our covers, while also offering a 2lb foam density option in our premium package.
No matter how dense it is, foam alone is not enough to properly support the weight of snow and ice that can build up on the cover in the winter. For this reason, hot tub cover manufacturers reinforce their foam with aluminum "c" channels on both sides of the cover. This aluminum strengthens the centre of the cover to stop the foam warping or buckling from heavy loads of snow or ice.
While not standard on all replacement hot tub covers, insulated hinge seals are critical to the energy efficiency of any hot tub cover. An insulating hinge seal is a piece of insulating foam that fills the area between the two sides of a hot tub cover when the cover is closed. Without a hinge seal, your hot tub cover will have a 1″ gap that is not insulated when the cover is closed, leading to a huge heat loss and increased energy bills.
2nd Layer - Vapour Barrier
Without some kind of protection, the insulating foam your hot tub cover would quickly become saturated by steam coming off the hot tub water. Not only is a saturated cover very heavy, its insulating ability is also greatly reduced. This is because air is a much better insulator than water.
To prevent the insulating foam from becoming saturated with water, hot tub cover manufacturers wrap their foam in a layer of vapour barrier. This vapour barrier is made of a poly plastic that is vacuum wrapped around the foam to ensure that there are no seams to let moisture in.
3rd Layer - Outer Skin
The last layer of your hot tub cover is the outer skin. This layer is designed to protect the foam and vapour barrier from the elements, as well as giving the cover a finished, more attractive appearance.
Vinyl Top Skin
The outer skin of most hot tub covers is made out of 28oz uv resistant marine grade vinyl designed to withstand the elements. This vinyl typically also comes in a variety of colours so that you can match your new hot tub cover with your hot tub cabinet.
The underside of the hot tub cover is made of a chemical resistant poly liner. This is because the underside of the cover is directly exposed to the steam coming off of the hot tub water; making it prone to damage and staining from chemical residues in the steam. Using a chemical resistant poly rather than marine grade vinyl prevents this damage and staining, increasing the lifespan of the cover.
The bottom skin can also be upgraded to include a reflective coating that reflects more heat back into the hot tub water; increasing the energy efficiency of the hot tub.
Straps with lockable safety clips are sewn into both ends of hot tub covers. One end of the buckle is sewn into the strap while the other one is attached to the hot tub's cabinet. When secured, these safety clips hold the cover onto the top lip of the hot tub; forming a tight seal that increases the energy efficiency of the cover. The safety clips can also be locked to prevent unwanted use of your hot tub.
Hot tub covers also have handles sewn into either end of the hot tub cover to make lifting and removing the cover easier.
While often overlooked, the stitching in a hot tub cover is crucial to its longevity. Simply put, poor stitching will rip more easily than more robust stitching. This can mean anything from a simple broken strap or handle, to something that renders the hot tub cover unusable; such as the two halves of the cover coming apart.
At Northern Hot Tub Covers, our covers are triple stitched for strength and durability. We also our stitching in 30 key areas of high stress to ensure the strength of our covers in the long term.
The last component of any good hot tub cover is the zippers. These heavy duty, rust resistant zippers are installed in the centre of the hot tub cover and allow you to easily remove the foam from the outer skin to make repairs to the foam or vapour barrier.