Insulation under UFH

[LadyBuilder]

Quick question, I am struggling with a decision. How much insulation should I have on the ground floor for the underfloor heating. I really would love to put it in the slab, but the slab extends to both front and back garden, so I don't fancy heating the whole lot... see elevation plan attached

 

I am also thinking that I need to get the SE to step the ground slab, so that the bit inside the house is higher and the outside is lower so I can stick the EPS on top.

DR 05_SECTIONS.pdf

[nod]

9 hours ago, LadyBuilder said:

Quick question, I am struggling with a decision. How much insulation should I have on the ground floor for the underfloor heating. I really would love to put it in the slab, but the slab extends to both front and back garden, so I don't fancy heating the whole lot... see elevation plan attached

 

I am also thinking that I need to get the SE to step the ground slab, so that the bit inside the house is higher and the outside is lower so I can stick the EPS on top.

DR 05_SECTIONS.pdf

Mine was spect for 100 mil insulation

But we decided on a block and beam floor So I decided to work to one course of block below DPC

140 insulation UFH then 75 mil screed

I know others on here have put in more

But this worked in really well with the build

 

Had I not needed to put a B&B floor in I would have packed in as much as I could afford into the slab

[le-cerveau]

Put a thermal break in the slab in the line of the external walls then you can heat it without heating all of London.

[Nickfromwales]

2 hours ago, le-cerveau said:

Put a thermal break in the slab in the line of the external walls then you can heat it without heating all of London.

How would one go about that ?

[le-cerveau]

 

7 minutes ago, Nickfromwales said:

How would one go about that ?

 

Our slab has one, this is the cross section of it from the SE drawings, it separates the house from the garage.

As you see the garage has thick ICF as an internal wall against the house.

The Garage also has a variable level (slope to the garage door) to cover Building Regs requirements, as we have a level access into the house.

 

[Nickfromwales]

2 minutes ago, le-cerveau said:

 

 

Our slab has one, this is the cross section of it from the SE drawings, it separates the house from the garage.

As you see the garage has thick ICF as an internal wall against the house.

The Garage also has a variable level (slope to the garage door) to cover Building Regs requirements, as we have a level access into the house.

 

 

 

That's all fully supported from underneath, but I doubt it could be applied to @LadyBuilder 's slab as its unsupported at the junctions where the thermal break would have to be. . 

[le-cerveau]

Re looking at it surely you would want the slab that is over the basement enclosed in insulation so the break would be where the slab is on-top of the basement walls, if the slab extends beyond that.

So insulate over the slab to the Ground Floor Walls, so the slab contributes to the "Thermal Mass" (I will be shouted at).

Then only put UFH pipes in the appropriate sections of slab.

I suspect it will end up being precast concrete spans as cast in situ could be difficult for that!

[Nickfromwales]

I think it's better to add some depth now, at the design stage, to allow an 'insulation slipper' for the ground floor maybe. 

Needs a proper think before living with the compromise.