Insulation confusion Ceiling 0.25 w/m2k

[aveatry]

Confused. Looking at the regs as I understand a refurb needs to acheive 0.25 w/m2k in ceilings, is that correct.
And can I acheive that with dritherm 32 which is 0.32 w/m2k
According to the updated Part L documents, the U values for existing elements in existing dwellings, the limiting U values will be:
Roofs: 0.16 W/m²K
Walls: 0.30 W/m²K
Floors: 0.25 W/m²K
Problem is the regs state in W/m²K but the spec for different thickness for dritherm is in R value. Here are the specs from the dritherm website.

So what thickness will acheive Floors: 0.25 W/m²K.
Its a kitchen downstairs ceiling I am planning on using the slabs as they will be pushed up from underneath and should self support before I re-board.
Thanks

 

[Wayners]

Board over with insulated board after insulating between timbers.
That's the norm.
You under building control? They will you

 

[aveatry]

No not under building control but I like to meet the standard where I can. There is nothing there at the moment anything will be better without going down the expense of PIR which I do not fancy in a kitchen even though it would be boarded over under board.
Confused anyway by the regs that say floors but not ceilings - I know that the ceiling below is the floor above but does the 0.25 only relate to ground floor floors that are suspended with an airbrick to outside and there is no regs for ceilings - if you know what i mean.

 

[jono_h]

There’s no regs for insulating between heated spaces - so if it’s the space between a kitchen ceiling and a bedroom floor (for instance) no insulation is needed.

Floors is the bit directly above the ground, which needs to be insulated to stop your heat disappearing into the earth or air.

 

[mikeey84]

U value is equal to 1/r value, so you should be able to convert R to U with a calculator

 

[Deluks]

You need to clarify whether this is a single story extension roof space, or has a room above.

If it's the former, it gets complicated with roof ventilation, if it's the latter, then as mentioned you don't need any. I put 50mm rockwool slab in mine to moderate sound between (downstairs) kitchen and bathroom.

 

[aveatry]

Thnank's for the help everyone.

You need to clarify whether this is a single story extension roof space, or has a room above.
If it's the former, it gets complicated with roof ventilation, if it's the latter, then as mentioned you don't need any. I put 50mm rockwool slab in mine to moderate sound between (downstairs) kitchen and bathroom.

Its actually both, it has a bathroom above and also has a small extension with pitched roof space the roof has been re done with breathable membrane. The kitchen is 2 m wide x 3.3m with the addition of an extra 400mm with is the extension.
Its a 60s house and I believe at the time it was an optional extra to have this 400mm internal, some of my neighbours have the bigger extension.

I am thinking at the moment to go 50mm dritherm 32 all over but then in the 400x2000 end with the roof space go 300mm loft roll over the 50mm. at that end the main joists stop and smaller 60mm high bridge the gap so 50mm will just about fill them and the loft roll over them.

 

[aveatry]

U value is equal to 1/r value, so you should be able to convert R to U with a calculator

Eh --- so one U = one R

 

[aveatry]

There’s no regs for insulating between heated spaces - so if it’s the space between a kitchen ceiling and a bedroom floor (for instance) no insulation is needed.

Floors is the bit directly above the ground, which needs to be insulated to stop your heat disappearing into the earth or air.

Thanks that makes it clearer now.

 

[mikeey84]

Eh --- so one U = one R

No, u value is equal to 1 divided by R value

 

[aveatry]

I have thought about the benefit that the bathroom above may be getting from the heat of the kitchen.
The bathroom floor is T+G with vinyl flooring. But the 400mm wide joist space in the kitchen below gos all the way from the kitchen across the living room - so the complete width of the house so any heat from the kitchen will be gone before it benefits the bathroom in any way ???
Also the kitchen is not heated but warms up overnight from a washing machine and dishwasher it can me cold in the day in winter but soon warms up when cooking.
So I am earing towards 50mm dritherm.