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Step 1
Location, Location, Location
The most important factor to consider is where you live and the location of your hot tub cover. Consider the amounts of sun, cold, rain, wet snow and snow your spa cover will receive. Each of these parameters is a factor in the selection of the correct hot tub cover, and will provide the best value for your dollar.
For example, if you live in a temperate climate, lets say Florida, you will be more concerned with rain than with the hot tub covers insulation. If you live in Buffalo, you will need to consider both cold and snow loads. However, if you live in Buffalo and a gazebo covers the hot tub cover, the only consideration will be the hot tub cover’s ability to insulate, keep heat in and heating bills low. -
Step 2
R-Value = A Measure Insulation Efficiency
The R-value for hot tub covers is a numerical calculation that is the measure of cover’s ability to insulate. The higher the number, the better the hot tub cover will keep the heat in and the cold out, and reduce your heating bill.
The R-value of a cover is determined by two main factors, the thickness of the foam core and the density of the foam core. -
Step 3
Hot Tub Covers - Thickness
Hot tub covers come in varying thicknesses. Most covers are thicker in the middle (at the fold) and thinner at the edges so rainwater will run off. This is called the cover’s “slope”. Typical cover slopes are 4” – 2”, 5” – 3” and 6” – 4”. For indoor environments, non-sloping or flat hot tub covers can be used.
The R-Value is calculated by multiplying the R-factor of the foam density times the thickness of the foam. For example, if the cover’s slope is 5” – 3” or 4” thick on average, the R-Value would be the R-Factor times 4. The thickness of the hot tub cover is a more important factor in the overall R-Value than the density as will be explained further below. -
Step 4
Hot Tub Covers - Density
Hot tub covers also come in varying densities of foam cores. Typical densities are 1.0 pound, 1.5 pound and 2.0 pound. The “pound” means the number of pounds of raw material used per unit when the foam is made. The foam core will be exactly the same thickness for each density, but the foam will be denser and therefore stronger.
Denser foam cores also tend to absorb less water as the air spaces between the foam is reduced. -
Step 5
Hot Tub Covers - R-Value Calculations
Thickness is the #1 critical factor for the hot tub covers overall R-Value. Keep in mind that the cover as a whole is a different R-Value calculation. The hot tub covers core is only one of the elements of the overall cover R-Value. The example below are ONLY for the hot tub cover’s foam core, and will mathematically prove that the cover’s thickness is a more important factor than the cover’s density.
6 inch – 4 inch slope, 1.0 pound foam = R-20.85
Average foam thickness = 5 inches
1.0 pound foam’s R-factor is 4.17 at 40 degrees F
R-value of the foam is 5 X 4.17 = 20.85
5 inch – 3 inch slope, 2.0 pound foam = R-19.04
Average foam thickness = 4 inches
2.0 pound foam’s R-factor is 4.76 at 40 degrees F
R-value of the foam only would be 4 X 4.76 = 19.04
A 5–3 cover with 2.0# foam has a lower R-Value than a 6–4 cover with 1.0# foam, and typically costs more!
