Upgrading loft insulation

[duncb]

Hi everybody,
I live in an end terraced house built around 1900 with a standard slate and underfelt roof.
I am looking at increasing the insulation in my loft, at present the existing insulation is squeezd between 100mm (approx) ceiling joist then covered over with loft flooring boards. the problem i have is i don't want to increase the depth of joist as headroom is already a problem due to roof slopes.
my ideas are,
(A) insulate between roofing rafters (celotex) then cover with a foil backed type insulation leaving the existing insulation in place.

(B) lift existing insulation and boards and replace insulation with something like celotex.

(C) do both the above.

Are there any problems to any of the above ways and which would you recommend.

Thanks for looking and reading, Dunc.

 

[RigidRaider]

I wouldn't bother insulating the actual roof - any heat retained by this would already have got out of the upstairs, wouldn't it?

The insulation has to go above the ceilings.

 

[ajrobb]

I wouldn't bother insulating the actual roof - any heat retained by this would already have got out of the upstairs, wouldn't it?

No. By insulating the roof, the loft will be warmer and less heat will be lost through the ceiling.

Anyway, in a Victorian property there will be minimal savings from extra loft insulation over and above 100mm. If you have dead loft space, then it is probably worth putting down subsidised mineral wool over the boards and at about 50p/m² it will pay for itself in a few years. If you need more storage, lift up some insulation to expose boards. The dramatic savings they claim are for uninsulated lofts.