Kingspan Insulation equivalents

[Last Cast]

Hi folks i'm doing a self build extension my drawings ask for kingspan kooltherm k7 to be placed between the ceiling ties and the same above to achieve a maximum u value of 0.11w/m2k. The floor asks 175mm kingspan kooltherm K3 maximum u value 0.15w/m2k.

Is there any insulation experts on here who could suggest an alternative cheaper product to kingspan to achieve the u values thank you.   

[the_r_sole]

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Edited September 26, 2019 by the_r_sole

[PeterW]

Floor you could go EPS but would require double the depth to get same uValue. ExtraTherm is another round here, as it Reticel. You can always look at seconds of PIR under the floor slab. 

[AliG]

For some reason architects love to specify Kingspan K7 which has conductivity of 0.2W/mK versus Celotex GA3/4000 or Kingspan TP10 at 0.22/0.23.

 

The Celotex is between 2/3 and 1/2 the price of the K7, the U-value would be around 0.13 instead of 0.11 for the roof.

 

You would get a similar saving and 10% worse U-value using Celotex GA3/4000 in the floor. There are other makes as mentioned above, generally any PIR insulation with a conductivity of around 0.22 will do. The Kingspan is considerably more expensive phenolic insulation which I would only pay for if it was absolutely necessary that it was a little thinner.

 

You can also sometimes buy seconds of these which are cheaper again.

 

The other thing I would note is that you cannot get 175mm insulation, you will need to buy 100mm and 75mm. This adds a bit to the cost and labour, although I am guessing that you are doing it yourself.

 

 

Edited October 1, 2018 by AliG

[A_L]

How about extruded polystyrene (XPS). You are going to need about 30% more by thickness.

https://www.jackon-insulation.co.uk/products/detail/jackodur-plus-300-gefiniert-gl/

 

There is always mineral wool batts (e.g. prorox SL920) or expanded polystyrene. Both with a lambda of 0.035 so about 70% more by thickness

[Onoff]

I've 175mm of "insulation" under my bathroom floor. 25mm eps then 150mm of pir above that. 

[epsilonGreedy]

  On 01/10/2018 at 21:35, AliG said:

The other thing I would note is that you cannot get 175mm insulation, you will need to buy 100mm and 75mm. This adds a bit to the cost and labour, although I am guessing that you are doing it yourself.

 

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When discussing this option with a screeding/UFH pro the other day he said "thin down first, thickest layer on top".

[PeterW]

  On 01/10/2018 at 22:19, Onoff said:

I've 175mm of "insulation" under my bathroom floor. 25mm eps then 150mm of pir above that. 

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  On 01/10/2018 at 22:22, epsilonGreedy said:

 

When discussing this option with a screeding/UFH pro the other day he said "thin down first, thickest layer on top".

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25mm EPS is quicker and easier to use as blinding than sand and it adds a thermal layer too. Also stops any DPM getting punctured. 

[Onoff]

  On 01/10/2018 at 22:25, PeterW said:

 

 

25mm EPS is quicker and easier to use as blinding than sand and it adds a thermal layer too. Also stops any DPM getting punctured. 

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I did a sand blind first dead level. Found it very Zen!

 

 

 

Then the 25mm eps:

 

 

Then the dpc:

 

 

Then the pir:

 

 

Think I put thick down first! Putting the 50 down first followed by the 100 would have been better I think.

[Ed Davies]

Seems to me that an advantage of two layers is that you can stagger the joints reducing any air paths if the stuff shrinks or moves a bit.

[Onoff]

  On 02/10/2018 at 08:40, Ed Davies said:

Seems to me that an advantage of two layers is that you can stagger the joints reducing any air paths if the stuff shrinks or moves a bit.

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Yep. I foil taped the joints on both layers.

[gravelld]

Kooltherm's lamba is 0.018 - that's why it's often specified - it saves space. Not that that's the only reason you should decide on an insulant of course; for newbuild you have many more options.

[ADLIan]

Plenty of pur/pir alternatives but kingspan has a virtual monopoly on phenolic foam so expect to pay top dollar for it.

[Last Cast]

Thanks for all the replies folks I should have said in my original post Im using TJI floor joists that I picked up as leftovers from a job. Regarding U values would building control let me away with 0.13 instead of 0.11 what are folks experience of this? 

[AliG]

These are the figures from the building regs. Assuming that the house you are extending has a decent level of insulation the limit for a flat roof is 0.18. This can be varied if other elements are better than the limits.

 

 

 

 

[curlewhouse]

"For some reason architects love to specify Kingspan K7 which has conductivity of 0.2W/mK versus Celotex GA3/4000 or Kingspan TP10 at 0.22/0.23." - I think for some it has just become the generic term like Hoover or (can't think of another one just now, but you know what I mean)  

[JCB400]

  On 01/10/2018 at 22:22, epsilonGreedy said:

 

When discussing this option with a screeding/UFH pro the other day he said "thin down first, thickest layer on top".

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The K103 spec sheet states "Where multiple layers of insulation of different thicknesses are used, the thickest layer should be installed as the outermost layer in the construction."