Your opinion on this statement...

[Steve]

I was speaking to someone very knowledgeable in our industry today. One of the comments he made was that all spas are comparatively efficient with the cover on.

Do you feel this is a fair statement?

Steve

[Mendocino101]

My guess is that for most spas of similar size...that it would be true of quality tubs...that yes the cost to run the spa would be of a comparable price....how ever some spas of some of the major manufactures do require to step up to 60 amps while other in the same class or size of spa will off of 50...

[wmccall]

Mom always said, "wear a hat, you lose most of your body heat through your head."

[Spa_Tech]

that all spas are comparatively efficient with the cover on

I have to disagree with this. Not that I have any specialized education in this, but I do have some empircal support for my postition.

As a service technician, Ive had the opportunity to own a number of different spas.

One of my first was a 110v API - a now defunct company that produced spas in the late 80's. The shell was insulated as I recall with about 4" to 5 " of foam and wasnt a full foam spa, The cabinet while complete was not insulated. This spa ran frequently to keep temps into the 102-103 degrees F range. My first power bill was up more than $40.00 just to operate the spa.

Later on I aquired a 1990 HotSpring Prodigy, which is also 110v. The percievable difference though is this spa is full foam, runs a small circulation pump, and only cost me $10.00 a month to run.

I think there's more to a spa's energy efficiency than a good quality 'hat'... er, a spa cover.

[stuart]

So if this is a true statment then there is no need to own both a heavy winter coat and a light fall jacket. Just get lighter and heavier hats!

Steve, does the guy that told you this go sking in speedos and tank tops as long as he has his stocking cap on?

[Sol_Dahbrishinsky]

Stuart

I just lost my breakfast at that thought

[Spatech_tuo]

Mom always said, "wear a hat, you lose most of your body heat through your head."

There is an assumption in that old saying that you've already bundled up with an approprite coat and merely need to be reminded about the head!! Mom would have had a fit if you didn't have a heavy coat on as well.

[wmccall]

There is an assumption in that old saying that you've already bundled up with an approprite coat and merely need to be reminded about the head!! Mom would have had a fit if you didn't have a heavy coat on as well.

Of course not, but the statement doesn 't imply that a cover is the only needed insulation.  But the best insulate spas aren't going to do nearly as well with no cover or a poorly fitting cover.

Steve didn't state where in the industry the person who said it works.   I would consider it a valid argument for a good quality cover without starting the old Thermopane/Full foam argument for the umpteenth time.

Of course Steve did say, "Is this a fair statement" Fair, I guess not, but it does have some validity.

[Lori]

Awfully extreme wording, to me.  All???  Some, most, many, may have been better qualifying words to use.

But what do I know?  Just an observation on the statement!!!

[ZzTop]

No Steve I do not buy that statement.

IMHO,

While a good insulating cover is important, the vessel (The Hot Tub) itself acts like a huge heat sink, pulling heat right through it.  Fiberglass and acrylic are very poor insulators of heat.  If you have ever owned an uninsulated fiberglass truck canopy you will find that it sweats because fiberglass is a very poor insulator.  The same thing happens with boats.  That is why the inside walls of fiberglass boats  are insulated with a very fiborous carpet to insulate it and increase its evaporative qualities to prohibit sweating caused by the conductive qualities of fiberglas transfering the cold temperature of the outside water.

So the more foam insulation on the underside of a spa the better to stop this transfer of heat loss and the more efficiently the tub operates.

In very cold climates, like the northern part of the US and all of Canada this is a very important factor to consider.

Of course because of the evaporative properties of hot water, the surface presents the greatest heat loss of all, so a good quality thermal cover and an insulating blanket are your best defense from losing surface heat energy.

Beyond the heater, there is only one other factor in operating costs and that is the size and number of electric pumps.  The fewer pumps the less it costs to operate.


Regards, Zz

[wmccall]

Awfully extreme wording, to me.  All???  Some, most, many, may have been better qualifying words to use.

But what do I know?  Just an observation on the statement!!!

I think Steve was intentionally being as vague as the person he quoted.  He may have more for us later and this was a feeler.

Bill
Always the conspiracy thinker

[Chas]

No Steve I do not buy that statement.

IMHO,

While a good insulating cover is important, the vessel (The Hot Tub) itself acts like a huge heat sink, pulling heat right through it.  Fiberglass and acrylic are very poor insulators of heat.  If you have ever owned an uninsulated fiberglass truck canopy you will find that it sweats because fiberglass is a very poor insulator.  The same thing happens with boats.  That is why the inside walls of a fiberglass boats  are insulated with a very fiborous carpet to insulate it and increase its evaporative qualities to prohibit sweating caused by the conductive qualities of fiberglas transfering the cold temperature of the outside water.

So the more foam insulation on the underside of a spa the better to stop this transfer of heat loss and the more efficiently the tub operates.

In very cold climates, like the northern part of the US and all of Canada this is a very important factor to consider.

Of course because of the evaporative properties of hot water, the surface presents the greatest heat loss of all, so a good quality thermal cover and an insulating blanket are your best defense from loosing surface heat energy.

Beyond the heater, there is only one other factor in operating costs and that is the size and number of electric pumps.  The fewer pumps the less it costs to operate.


Regards, Zz

Personally, I agree with ZZ. I would add one more item for consideration: Heat will travel in any direction: it always goes from hot to cold.

The idea that 'heat rises' is incorrect. Hot air is lighter than cold air, and hot air rises (unless you put it into air that is hotter still...). I think that is where the false idea that a spa's cover is the most important part of the insulation comes from. If you put a 6" thick cover on an in-ground spa, and shut off all motors and heaters, it will be cold in a couple of days. Do the same with a full-foam spa and it will lose only a couple degrees per day. It may take it weeks to get cold.

And before anyone tells me to go stick my hand over a candle: I know that the heat from an open flame also tends to go straight up. But the radiant heat from a campfire goes in all directions, including down into the ground.

[Bobb]

From a thermodynamic standpoint,  the rate of heat transfer is a direct function of the difference in temperature between a fluid, and the boundary layer of the material which surrounds it.  Yes heat radiates in all directions.  However, as those of us who have held a foam cup of liquid ( pick your liquid )  can attest,  the boundary layer of the foam, nest to the liquid warms to a temperature near the liquid, and resists further transfer.  If the top is open, thermal flow will keep a continuous supply of cooler gas close to the liquid, and a majority of energy will be lost from the top. Lids and other devices retard this transfer by restricting the thermal flow.
BobB

[Mendocino101]

lol...did I mis read this question or statement...I thought what was being asked or suggested was that most spas of same size cost the about the same (energy) to operate....did I totally miss it...

[huh?]

Taking the devils advocate...I would be a little more likely to agree.  Look at the way we build houses.  The attic is insulated and the walls are insulated...but not the basement floor.  Heat rises, otherwise hot air balloons would be less enjoyable.  IMO.