Calculations pls!

Hi all,

here's a question for you, as you know i am having a few problems convincing my contractor that insulating my new swimming pool is a good idea. It has been suggested to use Kingspan underneath and around the sides of the pool. He is now saying the Kingspan will not withstand the weight. So i am trying to do my own calculations based on Kingspans own specifications.

So basically Kingspan are recommending Styrozone H350R which has a compressive strength of 300 kPa...which is 43.5PSI according to this online calculator -

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say that the pool is 2 meters deep. Water weighs 0.036127 pounds per cubic inch according to this website -
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2 meters (80inches) of water weighs 80 x 0.036127 = 2.9 pounds.

Add in say 5 inches of concrete for the base of the pool which weighs around

2400kg/m3 (0.086 lb/in3) according to these websites-
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and
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we have 4.3lb/in3

So, bringing this together-

water @ 2 meters deep = 2.9psi

5 inches of concrete = 0.43psi total weight on the Kingspan= 3.33psi well within the 43psi Kingspan say their product can withstand.

Are my calcs anywhere near correct?! I doubt it, but welcome enlightenment and discussion!

Cheers all!

Greeny

Reply to
Mr Sandman
Loading thread data ...

Mr Sandman coughed up some electrons that declared:

OK -

Let's try it in SI units (or powers thereof) all the way.

The 300kPa max compression pressure is a fairly normal figure for insulation of this type.

1m3 of water has a mass of 1000kg (at 4C) and a weight of (near enough) 10kN, so 1m deep is 10kN/m2 or 10kPa. 2m deep gives a pressure at the base of 20kPa.

So water loading is no where near the limit. Concrete is double-ish the density of water so your 2400kg/m3 is quite reasonable. Let's call it 6" of concrete for good measure, so that's 15cm or 0.15m thick.

Mass of 1m2 of concrete of that thickness is therefore 2400 * 0.15 = 360kg or a weight of about 3.6 kN so that's a pressure of 3.6 kPa.

Add the pressures and you've got 24kPa good enough. That's practically the same as your answer despite my gratuitous roundings.

No where near the load limit of 300kPa.

Or looking at it another way, 1m2 of Kingspan can support 30 tonnes, so your pool would be good to 29m deep (with a bit spare for the concrete)!

Cheers

Tim

Reply to
Tim S

Wow thanks for that Tim!

Will tell the pool man not to worry!

Steve

Reply to
Mr Sandman

Maybe it's the extra couple of grand for the kingspan that's putting the contractor off, unless you have agreed to pay extra for it, and extra on top of that for it's installation of course.

FWIW, it's not going to make a blind bit of difference to the water temperature as 90% of the heat will be lost to the air above the surface.

And BTW, no one has calculated the weight of the reinforcing, IE the steel rebar, or the tiles, or twenty fully clothed drunks.

Reply to
Phil L

Because they are insignificant.

Reply to
dennis

Phil L coughed up some electrons that declared:

That I agree with. But I wanted to answer the question as put.

The piss heads make negligible difference. Their density is similar to water, so the extra loading will be their sum volume spread out over the pool area - or to look at in another way, if they are all mostly submerged, how much higher does the water level go? We've established it can go to 29m before the Kingspan is fully loaded.

As for rebar and tiles, stick another couple of inches on the concrete's contribution to loading pressure - it's still negligible.

Cheers

Tim

Reply to
Tim S

If it is a pool which is totally full (i.e. overflows into its gutter), Archimedes could tell you the impact of the drunks, naked or not, however dense they are.

Reply to
Rod

If you're having 125mm concrete before you have the insulation I'm not sure how much you would notice whether it's there or not.

Reply to
OG

"Phil L" wrote

Is the pool indoors or outside? Maybe it will be outside but covered - if so the insulation may make a difference.

Phil

Reply to
TheScullster

One other point to consider is that presumably you will still want to builder to provide a warranty on the completed pool - given that you are changing his design.

-- Nige Danton

Reply to
Nige Danton

Swimming pool base is above the Kingspan, he recommended a steel reinforced concrete base of 7cm thick, but im specifying 100mm minimum on the Kingspan to make it stiffer.

Steve

Reply to
Mr Sandman

Yes the pool is outside, solar heated, two of them (3x6m) plumbed in as one. There will be a high quality cover on each for insulation obviously!

Steve

Reply to
Mr Sandman

Yes, but my point is that 100mm concrete will reduce the insulation effect of the Kingspan layer. I'm not sufficiently au-fait with calculating thermal transfer rates to come up with a figure, but I'd have thought that there would only be a pretty marginal benefit in having the added insulation as the temperature differential across 100mm concrete will be fairly high, so rather than insulating water at (say) 18C from subsoil at 12C, you'll only be insulating against concrete at say 14C anyway. What depth of Kingspan were you thinking of having?

Reply to
OG

Rod coughed up some electrons that declared:

Yep. But the thought of fat naked drunks running through town shouting "Eureka" kind of makes my brain hurt ;->

Reply to
Tim S

Swimming pool water will be almost at constant temperature. The heat capacity of the concrete base is irrelevant. The kingspan's effectiveness will be no different with thicker concrete. The thermal flow will be much reduced by te kingspan.

I doubt if a swimming pool would get much use at 18degC.

Reply to
<me9

I cant see how the base will reduce the insulative effect, if anything it will act as a heat bank holding heat in. In fact i could heat the pool from the bottom rather than buying an expensive heat exchanger...hmmm....

Steve

Reply to
Mr Sandman

As I said a long time ago the soil itself is an insulator.

Some small point in kingspan down the sides (shorter path to air) but no point at all underneath.

Reply to
The Natural Philosopher

Although the Kingspan isn't (hopefully) going to actually collapse under the head of water you place over it, is its cellular structure going to actually move as you fill the pool, causing cracking of your concrete?

I think I'd rather prefer advice from a structural engineer (whom you can blame if something goes wrong!) than anonymous(ish) opinions on here... :-)

Reply to
Frank Erskine

Agreed and hence my earlier comment about warranty and changing the builders design.

-- Nige Danton

Reply to
Nige Danton

Not so sure myself... If the pool has its covers on (which it will most of the time) the losses to evaporation and convection to the air will be greatly reduced. If you are heating it above the nominal ground temperature (which IIRC is fairly constant year round once you go down a few feet), then the insulation ought to reduce the rate of conducted heat loss quite dramatically. What proportion of the total losses they comprise however I don't really have a feel for.

Reply to
John Rumm

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