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Help With Adding Insulation To My Qca Hot Tub With Additional Insulation

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I posted most of this info in another thread explaining my experience with QCA spas, when someone asked about them, but figured it should have it's own thread to ask the questions I needed help on.

I can say I own a QCA spa from Home Depot and it is very much under insulated. They insulate them better on the models from the full service dealers though from looking at their web site of those dealer models, but after 1.5 months of use in my unseasonably cold NE climate right now, my tub is severely under insulated based on 891 KWh extra needed @ 0.119 per KWh = $106.00 to keep it at temp during the last month with average outside temp of 15 degrees. Granted we have been averaging at least 20 person hours per week (meaning 3 people for 1 hour = 3 person hours), and one night 2 weeks ago we had a party with 3-5 people in the tub for 6 hours straight, so the cover has been off a lot while someone is in it and I know this limits the benefit of insulation while soaking with the cover off.

I decided to add additional insulation last night by using rolls of R-19 insulation with face side facing out on the inside of the metal frame, and also added 1/2" of (reflective side facing center of tub) TUFF-R sheathing board between this additional insulation and the tub as well. We shall see how much this helps for the next bill. I spent about $110.00 on insulation and 2.5 hours of time to insulate it more. I only partially insulated the outside 1/3 on each corner on the side with the access panel and used scrap reflective sheathing pieces used for the other sides to duct tape the area where the access door is. It is not completely seals, but I am hoping this will be enough to cut the power cost in half at least and hopefully more.

I figured this is a base starter spa as our first spa, and we got such a low price on it ($3000.00-350.00 instant rebate) and then I called Home Depot and got them to knock another $300.00 off based upon all my large purchases there over the years. So the net cost before Ozonator & sales tax was $2350.00 for the Monte Carlo model that holds 6-7 persons. I got this for my wife since she has wanted one for 3+ years now, but I was concerned after the newness wore off it would end up sitting idle most of the time so I did not want a major purchase that costs electricity to go waste. So far, it has been used so much by her, myself, and 4 kids and our friends and the kids friends that the power bill has climbed a lot with the cover off while soaking so much while the temp is so cold.

Even though the dealer models are better insulated (based on their web site) and I never knew the Home Depot models had less insulation than those models listed on their web site (no one told me this), I am pretty happy for the price even having to add insulation myself as long as I can get my power costs down from this insulation add-on I did. Sure it only has 30 jets, but we are fine with that amount and my younger kids always want to turn the jets off anyway. So other than the very poor insulation on the discount store models, I am pretty pleased with the spa. I know, I know, I got what I paid for with regards to to poor insulation, but this was a first spa to make sure it would get continuous use to later just ify an better one when the time/budget is right to do it.

I do have a couple of questions for the gurus here.

1. My spa came with only a 3"-2" tapered cover and now that I provided more insulation to the sides which combined with the original insulation should get me around R-24-25 side levels, would paying for a new 5"-3" cover now be worth it to save enough power costs to pay for the cost of such new cover with my temp likely averaging 20 degrees for the next 3 months?

2. I have to assume that the bottom of the tub is likely under insulated as well and is it worth the time/effort to undo the wiring and lift the tub in the spring to insulate the underside of the tub and will it save much power costs to go through the hassle?

3. Would spraying expanded foam on the inside floor be enough additional insulation for the most part rather than go through all the time/energy/cost to unwire it and rewire it by adding to the bottom of the tub from the underneath side?

4. How much heat is normally lost to the underside of a tub? Mine is on a 2x6 PT base with 4x6" PT beams sitting on 3" of crushed 1/4 rocks. There is a 8d nail amount of space between the 2x6 PT decking also.

TIA for any help figuring this out.

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No one has any info/advice yet?

I figured some of the gurus would have answers for at least one or two of these questions quicker than this. I must just be impatient. lol

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I can't believe not one of the gurus here has any ideas about this.

I know with the cover on the heat will try to seek cold through the sides and likely the bottom too when it cannot rise out the top, but on a wood base compared to a concrete base I would assume it will be lessened out the bottom. Does this make any sense since wood itself is a pretty good insulator? SHould I just throw some insulating batt down on the bottom for the winter just in case?

How about the cover? Would going from the cheaper OEM 3">2" tapered to a 4>2 or 5>3" cover justify the cost to save enough energy over that 3>2 cover. This one must be a simpler question to answer since we all have covers right?

I know some of the gurus are also dealers so they probably do not like people buying these cheaper tubs and doing the work afterwards to better insulate them as this might cut into their sales. I will say my budget would not have allowed even getting a tub based on the local dealer prices where I live. The cheapest I could have gotten was a small round D1 brand tub @ $5,000.00+ that was over twice the money I paid which was way too small for my family and we would have regretted it within the first week if I got it. So this tub from Home Depot was about the only thing I could have gotten within budget at this time or anytime in the next couple of years with this economy as it is.

Hopefully someone can offer some advice or info about what else I can do to improve the efficiency of my tub that I have.


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I'm no guru but I'll share my thoughts...

That little round D1 tub was around $3700 in my market. Can't remember exactly but it was definitely under $4k. A nice tub, I thought.

Working backwards through your questions, starting with #4. I don't know how much heat would be lost through your base but I wouldn't worry about it. I know the ground can freeze and temps can be below freezing in the ground but your 2x6 PT base will provide a bit of insulation. Comnpared to siting on concrete, as most tubs do, the PT base will probably conduct less heat away from the tub.

#2 and #3 - Insulating the base woud provide some benefit but I don't think it is worth foaming. If you are really worried about it could you use some type of batt insulation tha could be easily applied and removed if needed? The manufacturers are used to foaming tubs and may have learned to avoid some problems with the process. You wouldn't really need to fill the whole void - just the outer rim of the bottom and leave a dead air space in the center.

#4 - You will get to buy a new cover soon enough. I would not replace the one that came with the just to try to improve insulation. Since you seem to be a hands-on insulation guy maybe you can fabricate some type of supplimental insulation for the top (maybe sides too if you want). Perhaps there is some type of durable material that you could fill with the inulation of your choice asn set on top of the tub and just remove it when you take off the cover to use the tub. The aesthetics might not be the best but it may help keep your heating cost down.

So here are a couple of crazy ideas. I am not saying that you would want tto do them but maybe they will give you some ideas. You could make an enclosure out of rigid foam insulation a little bigger than your tub. You could make it single wall, double wall or double wall with a void that could be dead air space or filled with insulation. Leave an access poit on the side where your equipment bay is. Lay some rigid foam on top of the tub. It will look like you hae aconstruction project going on all winter because the rigid foam is a noticeable color but it would reduce your heat loss. just taek iti down in spring and resurect in the fall. You could do something similar with waterprooffabric bags of insulation placed around the tub.

I don't know if any of this makes sense to you but I felt bad that no one had come up with any solutions that might help you. The good news is that you are getting plenty of use and enjoyment out of your tub.

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Thanks for the reply Spawn. It is greatly appreciated. The round D1 seemed nice enough but the foot well seemed too shallow and it just wasn't big enough for my family either. I think they quoted they could go as low as $4400.00 for it at the local spa dealer.

One of the reasons I went with the 2x6 wood base is for the extra insulation it should provide, but with the 8d nail spacing it is not sealed so some air from underneath gets past the 2x6 wood base. I am thinking about using some of the left over rolled batt insulation to just lay down on the floor of the tub except for the area near the motor/pump since I already have it. I am considering buying some expanding foam to put a 2" coating on the underside of the shell to also help with insulation just in case the power by chance goes out for more than a couple of hours because of ice storms. My local town owned power company is excellent in this regard and I almost never even lose power and if I do it is only for a couple of hours. But last year we had a really bad ice storm and although I only lost power for about 3-4 hours At my house, some of the high elevation areas of town lost power for 3 days. :blink: I would hope that doesn't happen again or in my area, but it is a concern now that I have a tub out there. This is one drawback of parameter insulating chambers that rely partially on motor use heat to hold water temp. If I lost power for 3 days at 10 degrees I worry my tub could not hold enough heat to keep from freezing. I am also thinking about getting a remote temp device to know what the chamber temp is as well because of this.

I have heard of canvas type covers that go over the hard cover to protect it and also add some layer type insulation as well, and I will have to look into that. If anyone has links for such a cover it would greatly be appreciated. When I checked out a D1 from a dealer who used it as his home tub, he had this canvas cover over the hard cover on another larger (very nice) tub he also had set up in his yard at his home. I do notice that at the seam in the center that the frost does not foarm along that center area like the rest of the cover. Not sure if it is because of the poor insulation with just the edge blck where it folds instead of a full seam block, or because of the sun heat from the cover caddy keeping the frost from forming.

Thanks again for posting and helping. It really is much appreciated. :D

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Well I now have 2 full months electric bills with a hot tub with the billing date being the 8th of every month. Since my mother got the oxygen machine a little over 2 years ago which eats more power I am using only January 8th of 2009, 2010 & 2011 for figuring my KWh used, but I did not have the full month from 12/9/10-01/8/11 with the insulation I added. I only had the insulation from 12/17/10-1/08/11 and the KWh used for the last 3 years for January are:

12/8/08-1/8/2009 = 1995 KWh @.119/KWh = $237.41

12/8/09-1/8/2010 = 1910 KWh @.119/KWh = $227.29

12/8/10-1/8/2011 = 2041 KWh @.119/KWh = $242.88

The water temp was consistently kept at 100 degrees BTW. It puts the increase when averaging 1/2009 & 1/2010 compared to the 1/2011 months cost of only a $10.53 increase in cost and an increased cost of $15.59 over just the previous year power usage. 11/8/10 - 12/8/11 was a jump of 488KWh over the average of the 2 previous years and this was a full month in 2010 with the spa but no insulation added by me. So it appears that by adding the insulation I improved the energy savings quite a bit. BUT, we used it a lot less after 12/8/10 and I would estimate only on average of we only used it about 4-5 man hours per week compared to about 20 man hours per week for the month BEFORE 12/8/10. The temp outside did average a mean average of 27 degrees from 12/9/10-1/8/11 compared to a mean average of 38 degrees in the previous month when the KWh used jumped 488KWh, so the cost should have gone up because of this not down. We used it a lot less though so.....

This tells me what is obvious. The more you go in with cold temps with the cover off and the pump running the jets, the more it is going to cost to heat/run the spa. BUT it also tells me that the cost to heat the spa with nominal use of about 4 man hours per week that the cost is not much AFTER I added the insulation. and this was with 8 days of not having the additional insulation added for this monthly period as well. So the best way to keep the cost down is to use it less in cold temps outside if in the mid 20s mean average like I have had and that if you use it less the additional cost for my cheap spa AFTER I added $100.00 of insulation. That would make it cheap and certainly less of a headache to keep it going even if not used than to winterize it for me. Of course we shall use it as we want without thought of energy cost now that I added the additional insulation and we have an energy efficient spa now by me spending about $100.00 for adding the insulation.

Of course this is not conclusive since I didn't use a meter on the spa to get an actual fully accurate HWh usage by the spa, but after looking at my average usage for the same month over a 3 year period and my oldest daughter moved back in for this latest year starting in November as well. I feel pretty comfortable in saying that the insulation helps a lot to lower the cost and make it worthwhile for others to do if they get a perimeter insulated tub in a cold climate. I also feel that if you buy a cheaper spa with less insulation and properly add insulation then you can get a very efficient spa for a lot lower price. Of course it is a cheaper spa and not likely to last as long, or have some of those better jets the high end spas have, but for our first spa I now believe I made the right decision getting a cheaper one and adding the insulation for me. Remember I only paid $2350.00 for my new spa after the discounts I got, so compared to the higher end spas I saved a bundle to get a first spa and to make sure that it gets enough use to warrant owning one.

I am very pleased with what I have so far. If I have to replace the pump motor sooner as well as the Balboa heater then I am still way ahead even if it ends up being used only a little amount of time. Down the road if/when I replace it I can decide whether it is worth the money for our use to get a top brand spa then.

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