Thin insulation for beam and block floor

[Dunmow]

We are doing  a self build and have beam and block floor with the following layers (starting from the top)

75mm screed with UFH pipes
to Visqueen isolating membrane
to 100mm Kingspan insulation
to Visqueen DPM
to beam and block

 

We want to change the insulation from 100mm Kingspan to something with a higher thermal resistance, but still maintain a maximum of 100 - 110mm depth of insulation. Can anyone recommend a thin floor insulation that we can use?

 

Has anyone used Warmup Insulated Underlay? Or vacuum insulated panels? Would you recommend it? Or can you suggest alternatives?

 

[Dave Jones]

If your outer skin is brick or block what you have proposed doesn’t work brick or block.

 

try 150mm of eps and 75mm screed no need for double dpc just one under the insulation married to the wall dpc is fine.
 

 

[bassanclan]

You can try an insulated floor system such as hanson jetfloor etc, where essentially you replace the concrete block with EPS and then put your layer of Kingspan ontop if needed. There are numerous systems available https://www.bison.co.uk/products/jetfloor/

[tonyshouse]

Thin insulation is very expensive, cheaper to drop the substructure 100mm and use an extra 100mm of insulation. 
 

aerogel and VIP’s are mega expensive, unaffordablly so 

[Dave Jones]

1 hour ago, bassanclan said:

You can try an insulated floor system such as hanson jetfloor etc, where essentially you replace the concrete block with EPS and then put your layer of Kingspan ontop if needed. There are numerous systems available https://www.bison.co.uk/products/jetfloor/

 

problem with these systems is you have to have your floor finished including under  floor heating etc before your walls are built as you cant work off them or stack materials etc.

 

Adds more unnecessary hassle to the build. You will have enough without making more!

[bassanclan]

I used a temporary plywood floor whilst the walls and roof were being built

[Dunmow]

^{We have already got the walls up (which are ICF) and the concrete beam and block floor in. We had also crossed off EPS based block and beam because the builders said it would get too damaged throughout the rest of the building process. Sadly I am unable to lower the level of the beam and block (if only we had realised earlier ?).}

 

^{So I am unable to increase the thickness of the insulation layer, but I could change the material I use, instead of 100mm of kingspan I could use for example 50mm of Kingspan and 50mm of something that has higher thermal resistance (up to a total thickness of 110mm).}

 

^Thanks!

Edited November 18, 2021 by Dunmow

[bassanclan]

Aerogel is the only thing you can use, but it is very expensive

[Olf]

13 hours ago, Dunmow said:

change the insulation from 100mm Kingspan to something with a higher thermal resistance, but still maintain a maximum of 100 - 110mm depth of insulation

Kingspan is a brand, not a material - in this case it is confusing, as Kingspan offers both PIR boards (yellow, lambda 0.22) and phenolic (pink, 0.18).

I'm assuming it was PIR that was originally planned, with phenolic at the same thickness you get 20% better insulation at 80% more price. Aerogel and vacuum panels are unlikely to be economical for self build.

Any reason for specifically 75mm screed? There are thinner options available, that would free some extra space for insulation.

[Dunmow]

You are correct, it was PIR boards (lambda 0.22) which I meant.

 

75mm screen (including the UFH pipes) was what the architect specified. Perhaps I will look at this option.

 

[Mr Punter]

If you use a liquid screed you can reduce it to 50mm, so gaining an extra 25mm insulation.  As above, the phenolic foam offers more insulation.  Switching to liquid screed and 125mm phenolic will give a u value of about 0.12 as opposed to 100mm of pir which will give around 0.16.

 

With ufh on a beam and block floor this will make a considerable difference.

[Adam2]

Could you insulate beneath the beam and block? Blown beads? No idea how effective/how much airflow you need to maintain etc 

[SimonM]

On 18/11/2021 at 19:00, Adam2 said:

Could you insulate beneath the beam and block? Blown beads? No idea how effective/how much airflow you need to maintain etc 

I believe its 225mm minimum