Bond Posted October 5, 2007 Report Share Posted October 5, 2007 Question: I need a new cover. I can purchase a 1.5 lb, 4 to 3 inch cover or I can upgrade this cover to 2 lb foam for $40.oo.I can upgrade to 5 to 4 inch for $100 more. I have been told by the seller that it is not worth the extra money. My question is is it worth it or is there so little energy saved that it will not pay back. Please do not post an I think answer. If anyone knows the real answer please post.I tried to find an answer in past posts but have been unable. Thanks Quote Link to comment Share on other sites More sharing options...
Dr. Spa Posted October 6, 2007 Report Share Posted October 6, 2007 It's somewhat difficult to say, without knowing the TRUE thickness of the foam. A "few" sellers of covers are, shall we say, exaggerating, or using nominal thickness measurements in describing their cover. Both in the thickness of the foam and in the density. The thin edge of the foam is most commonly grossly "exaggerated". If a cover technically is made from 4" tapered to 2" foam, they seem to think they can exagerate it to 3" and no one will catch on. Technically the taper is suposed to be across the entire 4' width of piece of foam. If you really want, I've got a foam density calculator I came up with here; http://www.rhtubs.com/_density-calculator.htm But, assuming for the moment that the measurements you're giving are the actual true measurements of the foam, and don't include the thickness of the vinyl......... R value can be figured by averaging the thickness of the foam, multiplying by the R value below, then adding about R-1.5 for the vinyl and polywrap. 1.5# foam = R-4.17 per inch thickness 2# foam = R-4.35 per inch Once you have the R value of the cover figured out you can then calculate the heat loss based on the temp of the tub compared to the average outside air temperature (this isn't really accurate as it wont take wind or rain into consideration, but is something to work with). Off hand, I don't have the heat loss tables for R value, but I'll try to find them later. Quote Link to comment Share on other sites More sharing options...
Dr. Spa Posted October 7, 2007 Report Share Posted October 7, 2007 Ok, I'm not 100% sure this formula is accurate as I haven't double and tipple checked my source, but assuming you know the true R value of your cover, enter some specs here and it'll give you the approximate heat loss through the cover over a 1 month period. http://www.rhtubs.com/_heat-loss-calculator.htm Quote Link to comment Share on other sites More sharing options...
Shaamus Posted October 7, 2007 Report Share Posted October 7, 2007 If your dealer is recommending against the 5x4 cover, I don't have a huge problem with the statement. Not everyone needs a semi-walk-on cover. However, if he's telling you that 2# foam is not worth the extra $40, he's either uneducated on the subject or just wants you to buy more covers from him. As a cover manufacturer for the last 25 years, I can tell you that the investment in 2# density foam is the single best upgrade you can purchase when you buy a cover. Denser foam absorbs less water. Water absorption leading to heavy covers is the #1 reason most people even buy a new cover. Also, with energy prices these days, you're going to pay off the $40 investment over the life of the cover and then some. Quote Link to comment Share on other sites More sharing options...
Dr. Spa Posted October 9, 2007 Report Share Posted October 9, 2007 heh heh heh Didn't have an opportunity too further look into this till today. Ran a few numbers through my "awesome" heat loss calculator, pulled out a electric bill to figure the costs, and it looks like it's costing me some $4,000,000 a month to heat a spa.......... hmmmmmmmmm, the power company isn't billing me correctly.....Should I let them know?........ Wait, maybe my calculations are wrong. So, I went and found an entirely different formula for calculating heat loss. Wrote the programming (that took like 2 minutes), ran the numbers again....... got the same exact results........ to the 5th place to the right of the decimal point... hmmmmmmm. ooops.......... The old results gave the total number of BTU's lost. I forgot, you have to divide that buy 100,000 to get therms, to then convert to kW. Ok, so I fixed it. Call it version 0.2 But it's better now. Gives the results in kW lost per month through the cover. One last thing for ya Bond. I remembered (was "reminded" actually) the other day, a number of years ago we made a 4" x 3" tapered cover, 1.5# foam, for a dealer back in Michigan. At the time we were concerned that the slope wouldn't be enough to properly shed water. They insisted, we agreed with the condition that we wouldn't warrant the covers against water puddling on them. About a year later the complaints started coming in. Some 20% - 30% had problems with puddling (I wouldn't be surprised if there were more, just that the people never mentioned anything of the problem)......We switch to a 4" x 2-1/2" taper and the problem never showed again. Ok, I'm not 100% sure this formula is accurate as I haven't double and tipple checked my source, but assuming you know the true R value of your cover, enter some specs here and it'll give you the approximate heat loss through the cover over a 1 month period. http://www.rhtubs.com/_heat-loss-calculator.htm Quote Link to comment Share on other sites More sharing options...
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