Roberts Hot Tubs
  • 510-234-7920
  • Robert’s Hot Tubs
    2343 Welcome Ave.
    Richmond, CA. 94804

Insulating Hot Tub Cover Specs, Features & Benefits

A high quality hot tub spa insulating cover can pay for itself in as little as 6 months? These covers, designed for strength, durability and longevity are constructed of the finest materials available.

The inner core of our Premium Insulating Covers covers are 1 lb. density, metal reinforced EPS foam & tapered from 4″ to 2″ to allow accumulated water to easily run off.

Many older, and some cheap covers are made of a flat foam (or foam with less taper) which tends to allow water to puddle, causing the cover to sag, allowing more water to puddle, eventually breaking the cover.

Foam density refers to the weight of a cubic foot of foam.  A 1.5 lb. density is generally the ideal for a 4″ thick cover. It has excellent strength and insulating ability, yet is light enough to maneuver on and off your spa. Lesser densities are NOT advised for a cover of this thickness due to it’s lack of strength.

Our 6″ thick, 1lb. density cover provides almost 50% more insulation value over a 4″ cover.  It’s stronger than a 4″ cover, yet weighs the same. Higher foam densities have additional strength, but only slightly more insulating ability.

One of the many options we offer our customers is upgrading to a higher density foam when additional strength is needed.  It’s perfect for areas with heavy snowfall, rambunctious children, large dogs and even deer.

The foam is wrapped in a 6 mil polyethylene sheeting that is heat sealed to prevent water absorption. Many cheaper cover manufacturers tape the poly sheeting closed to save costs, but the tape quickly fails and the cover will start absorbing water, getting heavier and heavier. As an option, the foam can be doubled wrapped for extra protection from water absorption.

The outer covering is a certified heavy duty marine grade vinyl which is highly mildew and UV resistant. It was initially developed as an awning material for the boating industry. It’s available in your choice of different colors and is sewn together with a highly UV inhibited commercial thread which won’t mildew or rot out like some cheaper covers.

There’s even reinforced handles for easy removal from your hot tub or spa and it comes with four straps so you can easily lock the cover down.

Features & Benefits of Our Premium Insulating Covers


1. Locking, Side-Release Tie-Down Straps

Each cover comes standard with four tie-downs equipped with locking child resistant safety latches. To assure the integrity and prevent the straps from ripping out (perhaps from high winds), the straps are sewn into the cover in four places, including the skirt. This makes them virtually tear-proof.

Besides aiding in keeping out unwanted visitors, the tie-downs, when properly used help to prevent strong winds from blowing off the cover. There is also the option of additional tie-downs.

The “locking latches” are molded after the quick release buckles found on sports equipment and have been specifically designed for spas! Each NMF Fastener may be locked down individually. They are quickly installed with three stainless steel screws (provided).

2. High Quality Zippers & Strong Polyester Thread

The zippers are one of the lesser important parts of a cover. However if anyone ever steps on your cover causing the foam to bow you’ll want to remove and turn over the inner foam core.

For this reason we only use zippers designed to maintain their “zipping” ability for years.. Besides having the largest teeth available (6mm), they’re rust and chemical corrosion proof. We quadruple stitch them for added strength.

With the entire cover being double stitched together, the thread is also an important aspect to consider (some cover manufacturers heat seal their vinyl together, but the seams tend to become very brittle in the hot sun and freezing cold).
The thread used in our covers is a 93#, UV resistant, bonded, Dacron Polyester thread.

The polyester part is what’s important, unlike cotton thread (or cotton wound polyester) it won’t rot out in a short period of time, and the UV resistance prevents any degradation from the sun.

“Bonded” means that it’s actually water tight and can’t absorb mildew causing moisture. The 93# is the weight of the thread and the entire cover is completely double stitched.

3. Tough, Marine-Grade Vinyl Available in Your Choice of Colors

With a weight of 30oz. (per lineal yard), the vinyl of these covers is the heaviest available. It also exceeds the specifications of “Marine Grade Vinyl”, and “Premium Grade Vinyl”.
Marine Grade Vinyl was developed for the harsh climates of boating and the awning industry.

To be classified as a marine grade, the vinyl has to meet certain requirements (whether these requirements are exceeded or not is another story). The vinyl used in our covers exceed all specified requirements of both “Marine Grade Vinyl”, and “Premium
Grade Vinyl”!

Unlike some covers where the vinyl cover is heat sealed together, another important feature of these covers is that they are completely double sewn together with the highest quality thread. Heat sealed seams become very brittle in the hot sun and freezing cold.

The vinyl in our covers are the thickest in the industry and include mildew inhibitors, UV stabilized coloring to prevent fading, increased resistance to chlorine and bromine and are available in 10 different colors . Please see chart below.

In addition, the vinyl’s backing fabric on our covers is reinforced, 100% polyester mesh. Unlike cotton backing, our backing will not rot, is mildew resistant and has exceptional strength compared to cotton backing.

4. Gusseted, Double Stitched Skirt in a Variety of Lengths

The skirt of a cover is another of the many important parts. It needs to properly protect the lip of your spa from the damaging rays of the sun, and be strong enough to use for lifting your cover.

These cover’s skirts are double stitched into the cover for strength, and gusseted to provide the best protection! One piece continuous skirts, which are easier to manufacture, have many inherent problems as compared to skirts that are gusseted (also called “slited”).

Gusseted skirts will hang much straighter and have less tendency to bunch-up under the cover, preventing a proper seal between the cover and the spa.

As the sun beats down on a cover, extreme heat can build up between the skirt and the outer lip of the spa. This intense heat can actually damage the outer lip of the spa.


A gusseted skirt allows this heat to escape, preventing heat damage from occurring.

The skirts are double sewn into the cover for extra strength and strong enough to lift even the heaviest of covers.

5. Strong, Reinforced Handles for Opening & Closing the Cover

Unlike the handles on many covers which tend to be a great weak point, these spa cover handles have been designed and engineered to be one of the strongest! Handles are great when the cover is new, but over a long period of time most covers eventually get a bit heavier.

Cover handles, having such a small attachment area can be easily torn off, sometimes tearing the cover. Our cover’s handles are made of extremely strong, 1-1/2″ wide nylon webbing. Additional stitching, and internal reinforcing make them some of the strongest available. One of the many options offered, is to have the nylon handles vinyl covered.

6. 2.5″ Wide, 20 Gauge Galvanized Steel C-Channel Support Beam

Running the entire length of each piece of foam, along the hinge is a 2.6″ wide, 20 gauge galvanized steel C-channel support beam. This is the heaviest gauge (thickest) reinforcement beam used in the industry, others tend to be 22 to 26 gauge.

Galvanized steel is used for it’s increases strength over aluminum, and also because of it’s greater resistance to chemicals (chlorine and bromine). C-channel is much stronger than lesser expensive T-bar others may use.

If the possibility of this C-channel rusting has been made a concern to you, it really shouldn’t be. The only way for this C-channel to rust is if the vapor barrier surrounding the foam is broken. If this happens the foam core of a cover will absorb water (getting heavier and heavier) long before the C-channel loses any integrity.

7. Polyethylene Vapor Barrier on EPS Foam Cores (Optional Double Wrap)

One of the many important features of an insulating cover is the vapor barrier surrounding the foam. The barrier used in our covers is a 6 mil. single-extruded, virgin bead, polyethylene sheeting. This extra thick sheeting is heat sealed around the foam core.

As an added feature the sheeting is vacuumed of air during the sealing process. This prevents the cover from “bloating” from any trapped air expanding, when the sun beats down on it. Many cheaper cover manufacturers tape the poly sheeting closed to save costs, but eventually the tape fails and the cover will start absorbing water, getting heavier and heavier.

One of the options offered on these covers is to double wrap the foam core with a second layer of polyethylene sheeting. This is something no other manufacturer offers and we highly recommend it due to the following.

Covers have a small hole on the bottom side of the vinyl covering to allow any accumulated water and condensation to drain out. As much as this is an absolute necessity, it also allows evaporating chemicals to rise up into the covers interior (needless to say covers with an open mesh bottom are the worst).

Over a long period of time these chemicals can start deteriorating the vapor barrier to a point where it becomes porous. The porosity then allows steam and evaporating water to penetrate into the foam insulating cores.

One day science will probably develop a better vapor barrier (although those wanting to sell lots of covers may not use it), but until then doubling up the polyethylene sheeting will extend the life of your cover.

8. 4″ x 2″ Tapered, 1.5 lb. density, or 6″ x 4″ Tapered, 1 lb. density virgin-bead expanded polystyrene (EPS) foam core.

The covers foam core is the “back bone” of every spa cover. Not only is it the main insulating factor, it also provides the strength needed for years of use. One of the important features of our foam is that it’s a virgin foam, rather than recycled. While both may have the same insulating value, recycled foam doesn’t have nearly the strength as the virgin foam we use.

The foam core of our Premium Covers are a 1.5 pound density, metal reinforced, EPS (expanded polystyrene) foam , tapered from 4″ to 2″.

The taper is necessary to allow accumulated water to easily run off. Many older, and some cheap covers are made of a flat foam which will allow water to puddle,causing the cover to sag, allowing more water to puddle, eventually breaking the cover.

Please note, these measurements are the true measurement of the foam itself. It is not a nominal measurement, nor does it include the thickness of the vinyl or vapor wrap (you’d be surprised how many others don’t use a “true” measurement, and add in thickness of the other materials used).

Foam density refers to the weight of a cubic foot of foam. A 1.5 lb. density is generally the ideal for a 4″ thick cover. It has excellent strength and insulating ability, yet is light enough to maneuver on and off your spa. Lesser densities are NOT advised for a cover of this thickness due to their lack of strength.

The insulating core of almost all spa covers is EPS (Expanded Polystyrene). The insulating value of this product is very specific, and is listed in the table below. Please note, the R-value shown is for 1 inch of thickness.

Foam Density           R-Value/in.
1.0 lb.                          3.85
1.5  lb.                         4.17
2.0  lb.                         4.35

All EPS foam of equal density has the same R-value!

R-Value – R-Value describes a material’s resistance to the flow of heat. The higher the R-value, the slower heat will travel or conduct through a material. Better insulating materials tend to have better R-values.

Heat Flows by the Following Three Mechanisms:

1. Conduction
2. Convection
3. Radiation

Conduction Conduction is the molecule-to-molecule transfer of kinetic energy where one molecule becomes energized and energizes adjacent molecules. A cast-iron skillet handle heats up because of conduction through the metal.

Convection – Convection is the transfer of heat by physically moving the molecules from one place to another. Hot air rises; heated water thermo siphons; forced-air heating systems work by moving hot air from one place to another.

Radiation – Radiation is the transfer of heat through space via electromagnetic waves aka radiant energy. A campfire can warm you even if there is wind between you and the fire, because radiation is not affected by air.

By definition, R-Values measure an insulation’s ability to resist heat loss by Conduction and conduction only. This measurement is why R-Values can be misleading. Hot tub and spa heat rises from the water by convection and radiation and heats the underside of your cover.

The heat then moves through your hot tub/spa cover by conduction. Increasing the covers R-Value reduces or slows the rate of conduction. There are also two ways to reduce the rate of convection, the first being a floating blanket and the second being our optional exclusive Reflex Energy Shield used on the underside of covers.

The FTC requires certain industries and products to undergo extensive independent laboratory testing to define their R-Values and manufacturers can’t influence tests one way or the other. What you see is what you get.

The Hot Tub & Spa industry IS NOT REQUIRED to undergo extensive independent laboratory testing to determine R-value nor are hot tub and spa covers. R-value testing is done on a more subjective basis and values can be artificially inflated by simply lowering or increasing the temperature during the test.

We are not required to follow the same testing procedures as mandated by the FTC, but Roberts Hot Tubs and does in order to give our customers fair and accurate decision making information.

When comparing the real R-value of hot tub and spa covers, it’s important to ask your dealer what temperature difference the R-value was calculated at. Our hot tub and spa cover testing are all calculated using a value of R-14 at 40 Degrees.

9. Multiple Layered, Quadruple Reinforced Hinge

The hinge is one of the most worked parts of a cover, and on cheap covers one of the first things to deteriorate thereby letting steam and heat escape. First of all, our covers do have a hinge (they’re not simply two half covers sewn together), the hinge is constructed of the same high quality vinyl as the rest of the covers covering. Our hinge is also four layers thick and is quadruple stitched for the longest life available.

With the current trend of cover lifting devises (which we highly believe in) the hinge is one of the most worked parts of a cover.

This hinge is constructed of the same high quality vinyl as the rest of the outer cover. It is not simply two halves of the cover sewn together, but is a one piece hinge, double stitched into each half of the cover.

One of the options available is additionally reinforcing the hinge by adding an extra layer consisting of the same 1-1/2″ wide nylon webbing the handles are made from. This upgrade consists of a strip of nylon webbing running the entire length of the hinge! While other covers hinges are their weakest point, this nylon webbing reinforcement makes these hinges the absolute strongest possible!

10. Continuous Hinge Seal

These covers have a continuous insulated “hinge seal” to prevent heat from escaping from an area most people don’t even think about. Most other covers have what are called “fingers” or “steam sealers” (below).

These are two pads that are placed on the underside of the cover, at the ends, between the two halves to prevent steam and heat from escaping when the cover is installed on your spa.

If you turn one of these covers upside-down you’ll actually see that they also push the two insulating halves apart (below), leaving as large as a one inch gap between the two halves. This is equal to having a hole the size of a basket ball in your cover, your INSULATING cover!

Exceeds ASTM Standards for Spa Cover Safety

ASTM, the American Society of Testing and Materials, has developed a standard for both pool and Spa Covers. This Standard, ASTM F 1346-91, establishes three separate cover classifications;

1. Power Safety Covers, typically found on swimming pools
2. Manual Safety Covers, such as the spa insulating covers and
3. Other Covers, which do not serve as a barrier for children under the age of five and do not qualify as a safety cover.

In order for a spa cover to meet the requirements for a “Manual Safety Spa Cover” it must meet certain requirements which include performance tests and labeling requirements.

Covers must be able to pass tests such as Static Load Tests for weight support, Perimeter Deflection Tests for entry or entrapment between the cover and the side of the spa and Surface Drainage Tests to see if a dangerous amount of rain could collect on the covers surface.

There are also requirements that include labeling in consumer information, warranties and on the cover itself. Labeling must contain the proper warnings and identify the product as a safety cover.