Pool wall insulation

Youngster

New member
Aug 5, 2010
2
Hi Everyone,
I'm a longtime lurker but this is my first post on TFP so go easy on me :) .

I'm planning to put in a DIY vinyl liner inground pool next spring. I'm still in the planning stages and am very concerned about heating costs(I'm in NH). I was wondering if anyone has insulated the outside walls of their pool with spray closed cell polyurethane insulation. If you install a pool with polymer walls would this have an adverse effect on them? Would the insulation hold-up to the elements and during the backfill?

I understand that most of the heat loss comes from evaporation. I'm just wondering whether it would be worth the effort to try and insulate the walls. I do plan on applying 1/8" foam to the inside of the walls.

Thanks in advance for all the responses,
Jeff
 

bk406

Well-known member
Dec 3, 2009
2,690
Central Massachusetts
Wouldnt do much if anything at all, really. The outside of the walls are "insulated" with backfill. A little foam on the outside wouldnt contribute to stopping heat loss. The vast majority, if not all heat loss comes from evaporation.
 

Melt In The Sun

TFP Expert
LifeTime Supporter
Oct 29, 2009
3,899
Tucson, AZ
If you really wanted to insulate the walls, you could just get a normal kit and have someone spray-foam the walls separately, for less money than they want for it.

I agree w/ bk406; you're not going to get 15-20 degrees difference. I would be surprised if you got any. Dirt is a pretty darned good insulator by itself.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,785
Pleasanton, CA
I would trust the Florida Solar Energy Center from the University of Central Florida over any other source since they are one of the leading research institutes in solar energy. According to this document, Figure 1 shows that conduction through the walls is minimal and probably less than 5% of the total heat loss.

Of course if you use a cover and eliminate evaporation, then convective and radiative become the dominate heat loss mechanisms but conductive is still pretty small.
 

Henry Porter

LifeTime Supporter
Nov 7, 2008
604
Sweden
I have insulated my walls and I think it's worth while atleast if you have a pool that needs to stayed covered most of the time.
The topsurface of the ground is constantly chilled down from wind/rain and dropping night temps and insulation prevent that enviromental impact from chilling down the top surface of your pool walls, so if there should be any insolation it's probabaly from the top and a couple of feet down, Further down my guess is that it becomes less and less important.
I loose around 1- 1,5 C during a night with my solar cover on and that is with a water temp of 86 and with a night temp that drops down to 57. And from what I have read from other swedish pool owners in my area that's pretty good.
If that can motivate the extra cost it takes to make an isolated pool! I don't know but it feels good now when it's done. For us that used celluar plastic was the cost not so significant if you consider the total cost of the pool.

EDIT: a couple of feet down from the surface is where I think insulation makes most impact and not a couple of inches that wrote.
 

teapot

In The Industry
Jul 25, 2009
574
London and France
I think someone missed out the decimal point! 1.5-2.0 degrees more likely.

Some helpful info:

http://www.poolinsulation.com/

A report commisioned by the above but carried out by a respected body the Building Research Establishment, all new pools in the UK must be insulated as part of our buiding regulations.

http://www.poolinsulation.com/img/brereport.pdf

The polystyrene and reinforced concrete block pools are very popular as you get insulation and considerable build strength in a very realistic price.



If that is not available, consider using insulated concrete forms (ICF) which are used for basement foundation construction and also whole buildings now, google it should bring you plenty of info.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,785
Pleasanton, CA
While interesting, keep in mind that the BRE report was commissioned by several commercial companies with interest in convincing consumers to insulate their pools so it is hardly independent research. But it doesn't invalidate it either.

Second, the report only really focuses on the insulation and heat loss through the walls and total ignore the other mechanisms of heat loss. You really have to put heat loss into context by comparing it to the total heat loss of the pool. No one is arguing that there isn't heat loss through the walls. Only that it is minor compared to the heat loss through the other mechanisms in most residential pools.

However, if a hard highly insulated cover is used which minimizes evaporative, radiative and convective heat losses, then and only then does conductive heat loss become dominant. But I would still argue, it is small. I would only consider insullating the walls if you were heating the pool with gas or electric and you had a highly insulated cover. Otherwise, it is simply not worth it.
 

teapot

In The Industry
Jul 25, 2009
574
London and France
Agreed Mas985,
I cannot find any reason with the type of pool I described not to build though. cost good, strength better than plastic or steel panels, insulation a bonus!
 

Youngster

New member
Aug 5, 2010
2
Wow, lots of real good information. My plan was to buy one of the Tiger foam insulation kits and spray the outside walls myself. For an inch of closed cell foam I believe you would get R-7 and a kit would only run around $600. I'm still not sure it's worth the effort or not. It seems like it would be inexpensive and fairly easy to do.
 

busterpace

Member
Apr 8, 2011
9
I am also new to the site but I tend to agree. I have a bi level home and half my lower level is 4' underground. When I remodeled I spray foamed the entire walls. From the cinder block up to the stick framed OSB walls. Then I went back and put fiberglass batt over that. R-20. No air movement.

I also used Tiger Foam. Why not spray the outside of pool walls, and especially the suction and return lines. Whats $600 on a $30,000 pool. I know the difference on a cinder block wall was great. The difference between touching a below grade wall without foam and with foam was night and day.

Dirt is 55 degrees. There has to be heat loss into it.
 

bk406

Well-known member
Dec 3, 2009
2,690
Central Massachusetts
The BTU required to heat a house for a entire winter is dwarfed by comparison for what it takes to heat even a relatively modest 20,000 gallon pool. Any kind of insulation on a pool other than a solar cover would do minimal, if nothing at all, to prevent heat loss. 99.9% of the heat loss from a pool is from the surface, not the walls. Save the $600 for something more useful :wink:
 

MajorDIYer

LifeTime Supporter
Feb 23, 2011
80
Sicklerville, NJ
This is an interesting topic. Anyone who has been camping knows the difference a 1/2" foam pad makes when used between the sleeping bag and ground on even a mild night. For someone who spends thousands every season on heating, even a few percent savings on that would add up over several seasons. It may pale in comparison to an insulating cover but it's also a one-time installation then forget it deal.

The problem I see is, the walls are only half (or less) of the ground-to-water conduction area. What about the floor? Would the pool be more prone to freezing in colder climates as well? Interesting to think about anyway.
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
Try this analogy, what difference does it make if the wall is insulated or not when the window is left wide open all the time? Yes, technically there is a difference when you insulate the walls, but it isn't something you would normally be able to notice. If you are planning to put three or four inches of foam on top of the pool when you aren't swimming, the way some people do with a spa, then it is time to talk about insulating the floor.
 

MajorDIYer

LifeTime Supporter
Feb 23, 2011
80
Sicklerville, NJ
Even though we're leaving that window wide open, we're still turning the heater on to warm the room. If we can use insulation to replace pumping in more heat energy, even to a small degree, is there a cost benefit over decades of pool use? With the way energy prices are going I wonder if the answer is that simple.
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
Yes, it will save some energy, and it doesn't hurt anything. So sure go ahead. I just think that there are better ways to spend that money, but that is a personal choice rather than an absolute statement.
 

armstrr

LifeTime Supporter
May 11, 2010
162
Sarnia, Ontario Canada
I am considering insulating the walls and floor of my pool with fiberglass door cut out panels. These are what are cut out for windows. Less than 2" thick r-12. A tigerfoam kit to fill gaps The ground temperature around here is about 50 deg.

I think this will help the swimming season start earlier and go longer. But one must keep the pool covered when not in use as evaporation will remain the largest heat loss... If you won't consider covering with a solar cover, you are likely wasting your time and $$.
 

MajorDIYer

LifeTime Supporter
Feb 23, 2011
80
Sicklerville, NJ
There is a great deal of information out there if you look for it. It seems to be very popular now with building things "green" and all.

What I learned boils down to this: yes, soil has a poor R-value but that doesn't automatically mean insulation will make a big difference. Despite being a poor insulator compared to other materials, the massive amount of soil under your pool makes having a few inches of insulation seem like nothing in comparison. The determining factor is moisture content. If the soil is completely dry, adding insulation does no more good than having a few extra feet of dirt under the pool. If the soil is very wet, though, that water can move heat away very quickly.

So if we want to insulate a pool, we should build an outer waterproof shell, line that with thick insulation, then top it with the pool liner, making a giant Thermos. And make sure to cover it well... otherwise don't bother at all :?