urgent advice needed - thanks

[ab12]

In the middle of having a kitchen extension. Brickie has nearly built up to damp. I have opted for the following floor make:

 

150mm hardcore

50mm sand blinding

2000 g  (500 mu) DPM

100mm concrete slab

1200g (300 mu) DPM

100mm   OR 130mm  OR  150mm insulation

DPM unsure about the g or mu value  may choose 1200g or even thinner?

75mm non liquid screed over UFH to reach finish floor level

 

I'm confused about the insulation part. Need to reach U value 0.18. 

 

walls, all exposed to outside with Cavity of 150mm between outer and inner walls.

 

Dimensions of internal  leaf walls are 5.6m by 3.49m , Area to be insulated: 19.54 m2. Exposed perimeter is 14.69m. PA ratio is 0.75.....can get

U value 0.17 with 100m Cellotex 

U of 0.14 with 130mm Celltotex

U 0f 0.12 with 15omm Cellotex

 

I have already purchased 6 sheets 2400mm by 1200mm Cellotex. 

Is it worth going the extra mile and have extra insulation so either 130mm or 150mm laid in 2 layers,

so 100mm sheets laid first followed by 30/50mm sheets 

OR 30/50mm sheets first followed by 100 mm sheets.

 

Please let me know your thoughts. Workers coming and laying hardcore and sand, I may need to dig a little bit more of the floor  if go for 150 mm insulation OR I can sacrifice on sand blinding layer by choosing 30mm sand blinding instead of 50mm sand blinding without needing to dig any more floor.

[JohnMo]

UFH more insulation is way better, stick in as much as you can.

[ab12]

Is the new building Reg U value for floor UFH 0.18 Or 0.15?

 

Just done a google search and its coming up as 0.15.

[JohnMo]

Read this post take learning from everything.

 

https://forum.buildhub.org.uk/topic/42827-cold-extension-insulation-issues/

[ab12]

14 hours ago, JohnMo said:

Read this post take learning from everything.

 

https://forum.buildhub.org.uk/topic/42827-cold-extension-insulation-issues/

Hi JohnMo

 

I have had a good read but can't see anu U values stipulated for UFH for solid ground floor slabs.

 

What is the best way to lay 2 layers of PIR boards e.g 100mm followed by 50 mm or vice versa.

Would it be better to lay 100mm first and then 50mm on top.

 

 

[JohnMo]

7 hours ago, ab12 said:

have had a good read

I was meaning take learning on board about the whole build of the extension and the issues you can have if you don't keep an eye out.

 

7 hours ago, ab12 said:

100mm followed by 50 mm or vice versa.

Would it be better to lay 100mm first and then 50mm on top

Not sure it makes any difference. But if clipping UFH pipes direct to insulation I would do 100mm on top.

[Conor]

You want 150mm minimum, 100mm and 50mm layers.