Floor slab insulation. Test my logic please?

[Russell griffiths]

The problem with all these comparisons is you are comparing the prices from the builders merchants 

if buying EPS you can deal with the manufacturer, pir manufactures won’t deal with you. 
I got my EPS100 at a third of the price of pir. 

[saveasteading]

2 minutes ago, Russell griffiths said:

a third of the price of pir. 

where, where, where please?

[SteamyTea]

45 minutes ago, saveasteading said:

wonder how much the temperature at 1m depth drops by the end of winter.

By the new mean yearly temperature. Ground at a metre depth is generally about the mean yearly air temperature.

But as I mentioned earlier, it is more complicated than that.

[SteamyTea]

Regarding the perimeter losses, a fairly accurate way to compensate for it is to work out the periphery distance, multiply by the square of the slab/insulation thickness. This will give you a volume i.e. 20m³.

Spread that volume over the floor area i.e. 0.2m extra thickness over 100m².

That will compensate for the finickity losses.

Alternatively add extra insulation outside the thermal envelope around the perimeter.

The Kore slab system, if I remember correctly, has that built in as part of the design.

[Susie]

I have been buying my insulation from https://www.insulationsuperstore.co.uk/

I have had multiple deliveries from them, at least 10. I have purchased rock wool and PIR only once did the delivery come on a huge truck most came on a small van and the drivers were very friendly, delivered from SIG or Markovich, with good delivery communication. The Rockwool I purchased by the pallet, the PIR by the sheet mixing my order 80mm and 100mm and spending the minimum for free delivery which meant I was not stacking rooms full and risking damaging corners. I was often getting discount codes or used my account points to get money off never paid the full price. 

 

[saveasteading]

18 minutes ago, SteamyTea said:

Ground at a metre depth

I meant after a winter of the ground source pipes removing the therms. 

 

They look like this but with arms and legs: 

 

10 minutes ago, SteamyTea said:

the finickity losses.

 

That needs an Ancient  Greek letter. 

 

15 minutes ago, SteamyTea said:

0.2m extra thickness over 100m².

You mean deeper to the perimeter? It makes sense to have deeper insulation round the perimeter, and shallower to the middle, but that isn't happening. It's just going to be a less efficient area of the building, balanced by the centre of the slab being over-insulated.

Perhaps PIR to full depth around the perimeter and 2 layers eps centrally is the pragmatic (and finicky) decision.

It is intuitive rather than proven, but I'm confident I could write a page of 'proof' for the building inspector if it was necessary... but it isn't and will just be our decision.

 

[SteamyTea]

6 minutes ago, saveasteading said:

Ancient  Greek letter

A bubble.

7 minutes ago, saveasteading said:

It is intuitive rather than proven

I think it is proven, but may have to ponder it a bit more.

Then do a bit of modelling.

Thermal losses can be quite accurately modelled using the cube root of the sum of 3 dimensions, 4 dimensions if you want to add in time. 

Or use a Fourier multiple sine wave calculation, but I never intuitely understood that.

[saveasteading]

12 minutes ago, Susie said:

buying my insulation from https://www.insulationsuperstore

They have the best of the quoted prices online at present, along with Insulation Wholesale.

 

Some others say they will match any quote but I resent that attitude and will tell them that they must quote their best price first as I don't give second chances. If they are too scared to do that then I don't fancy their service or security will be great either. What is the point of matching another quote unless their is some other benefit?

 

@Susie was this recent?

[saveasteading]

4 minutes ago, SteamyTea said:

the cube root of the sum of 3 dimensions, 4 dimensions if you want to add in time. 

Or use a Fourier multiple sine wave calculation, but I never intuitively understood that.

This is getting into science fiction. I need a lie down.

What is the cube root of time anyway?

Or is it a way of proving that  that entropy isn't what it used to be?

[SteamyTea]

16 minutes ago, saveasteading said:

is it a way of proving that  that entropy isn't what it used to be

It is, by definition, not what it was.

 

[Gus Potter]

21 hours ago, saveasteading said:

I'm aware of that but reminders are no bad thing.

I wonder how well a soft packaging eps would fare beneath 100mm or more of PIR and a grand piano on top. perhaps with a big enough dish under each wheel it would be ok.  This is whimsical: I am not saving amazon packaging to try it.

Interesting! 

 

In SE terms. For fun let's take a grand piano. That weighs about 550 kg and has three legs. Thus about, say 183 kg per leg. A "20 -22 stone" rugby prop can in the modern fast game can be 110 kg, but say the team just needs dead weight, so take the prop as 140 kg. Not far off the load from a grand piano leg. But the piano does not walk about, the prop does so lets add a bit of dynamic load to their foot fall. Say 20% thus 1.2* 140kg  = 168kg. And all of a sudden we realise that locally on a screed a big lad has something to say and a point to make!

 

Welcome @rjclark71 to BH! 

 

To delve into @saveasteading question do we put EPS on top or below the PIR? In this case we are looking at a ground bearing slab that is not supported by (at the edges) or transferring load to the perimeter foundations. There is a cement based screed with underfloor heating pipes (UFH) embeded in it. 

 

Now we have a point load ( a piano has a larger foot than a shoe, take the shoe heal as this load is more concentrated. The load from the heal of the shoe gets spread out at roughly 45 degrees down through the screed and onto the first layer of insulation. It then gets spread more down through the insulation thickness. Therefore the compressive stress gets less the deeper you go as the load is spread out more. In conclusion it makes sense to put the weaker insulation on the bottom as the loads are more distributed. 

 

 

 

 

 

[saveasteading]

2 hours ago, Gus Potter said:

weaker insulation on the bottom

Yes, but does the floor screed move or crack under the foot of Xander Fagerson?

And will the tv packaging be strong enough?

[Susie]

3 hours ago, saveasteading said:

They have the best of the quoted prices online at present, along with Insulation Wholesale.

 

Some others say they will match any quote but I resent that attitude and will tell them that they must quote their best price first as I don't give second chances. If they are too scared to do that then I don't fancy their service or security will be great either. What is the point of matching another quote unless their is some other benefit?

 

@Susie was this recent?

Still ongoing. Hope to put my last insulation order in soon.  The points you get can be used across all the group sites but I haven’t purchased much more on the other sites.

 

[Gus Potter]

20 minutes ago, saveasteading said:

Yes, but does the floor screed move or crack under the foot of Xander Fagerson?

And will the tv packaging be strong enough?

On my phone but quickly. He went to Strathallan so his weight may be under estimated..

 

Yes technically the screed will crack further. The screed had no residual tensile strength due to the UFH pipes. So it really works in direct beating  only.
 

On balance the packaging is likely not suitable.

 

The screed has a small aggregate and thus aggregate interlock is less reliable. But the shrinkage still remains.

[SteamyTea]

Found that old spreadsheet about ground temperatures.

 

Quick, simple chart from it.

 

[G and J]

Presumably that data is for open ground.   
 

Under my slab will, I imagine, be rather different.  
 

It’s dry ground, no watercourses or the like.  So what temperature should I use for my heat loss calculation for the underfloor insulation?

 

(This particular horse has now bolted, but it’s still of interest.)
 

 

[Russell griffiths]

17 hours ago, saveasteading said:

where, where, where please?

 

very bad screen grab, try and zoom in. 

[saveasteading]

1 hour ago, Russell griffiths said:

zoom in. 

It's good enough to find them. Thanks muchly. 

S and B EPS.

 

Their website is comprehensive on strengths and insulation, and some other products. But nothing on where to buy or costs, so I've sent them an email.

 

Strangely the strength and insulation vary by thickness, presumably a manufacturing density thing. And they make consciously stronger stuff too.

k = 0.036 average.

[dpmiller]

graphite EPS takes it to 0.031 or so

[SteamyTea]

2 hours ago, saveasteading said:

k = 0.036 average

 

41 minutes ago, dpmiller said:

graphite EPS takes it to 0.031

Not really that much difference.

 

[saveasteading]

47 minutes ago, dpmiller said:

graphite EPS takes it to 0.031 or so

I'm expecting that to be much more expensive.

[dpmiller]

4 hours ago, saveasteading said:

I'm expecting that to be much more expensive.

pennies, as I recall