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Heavy Hot Tub Covers Waste Energy

Heavy Broken Spa Covers Waste Energy. I saw this advertised on line the other day. When I went to check out the guys website, guess what he's selling? Rigid foam spa covers that will end up heavy or broken, usually within two years. To me this is like a coat salesman telling you wet wind breakers won't keep you warm, here you need to buy this new dry wind breaker and go play outside in the rain.

He's hoping you won't notice that he's selling you the same thing you're replacing now. If you're replacing your spa cover because it got heavy, Before you buy the next one, perhaps it would be good to think about why the old one got heavy?

What causes the foam spa cover to get heavy is that it traps moisture inside. Foam board is used in many insulation applications. It can be used around refrigeration storage areas like in a super market. Layers of rigid foam board is what keeps the refrigerated section cold while the customer area is still warm. When used in this application the foam is not subject to warm moist steam. As long as the foam stays dry it has a predictable insulation value. But if the foam were to have moisture in it instead of the little air spaces it uses to insulate, it would have no insulation value at all.

If you were trying to invent a way to get foam to saturate as quickly as possible, the design would involve lots of steam under it and a cooler temperature on top of it. You couldn't get water into it faster even if you tied it to the bottom of your swimming pool. Why? Because water molecules are bigger than steam molecules. Steam can get into smaller spaces faster than water. And once the steam cools, it condenses back into water, displacing air in the foam as it does.

Long before you notice the spa cover getting heavy, moisture has begun to replace the air spaces in your cover. When it does, the little insulation value that cover might have had, goes down dramatically. From whatever it may have been when you first put it on your spa it has gone down to as much insulation as a wet piece of plywood by the time you actually notice it got heavy.

You might get fooled into thinking that it is still insulating well because snow won't melt off it. Unfortunately, you would be wrong. Snow won't melt off a frozen pond either but it doesn't mean the ice is insulating the water. When snow falls on a saturated foam spa cover, it freezes the moisture in the cover because it is laying directly on the cover. The water of your spa is never in contact with the foam since the foam is resting way up on top of the acrylic of the spa, usually about a foot above the water surface. What's happening is the warm spa water is evaporating into steam. That steam is rising, because that is what heat does, until it hits the bottom of the frozen spa cover. Then the steam cools and turns back into water. The water, now cooled, falls, because that's what cold does, back into the warm spa water, cooling it off.

So if you wanted to invent a radiator to cool off your warm spa water this would be the perfect design. Put a block of frozen foam over the water. Pile a bunch of snow on it to keep the hot tub cover frozen and go over and listen to the power meter buzz. Instead of just getting another of the same type of spa covers that will end up in the same condition, shop around for one that is designed differently. Look for a spa cover that will insulate the water from the water surface, without rigid foam.

About the Author

The Author is a business owner with more than twenty years experience. A former Police Sgt, Pilot, Heavy Equipment Operator, Trained Mechanic, and accomplished motorcycle rider he enjoys riding the back roads of Washington on his Harley Davidson, Police Edition. Please visit his website SpaCap.com Spa Covers.

NASA ISS On-Orbit Status 3 January 2011
All ISS systems continue to function nominally, except those noted previously or below. Underway: Week 6 of Increment 26.

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