Updating loft conversion insulation

[Munnster1]

Hi all,
We bought a house which needs some renovating 1930's which has an existing loft conversion we believe from the early 80's. We have looked in the remaining loft cavity and through small holes in the ceiling (due to recent rewire) and have found the current insulation is just rock wool type and not particularly thick (approx 10cm max) we are on a tight budget but are planning on living here long term and want what's best for thermal efficiency while not going over the top on cost/replacing when not necessary. The roof is new having been replaced just before we bought 2 yrs ago.

Please could you tell me what you would do? Replace insulation where can reach or replace all including under current plaster board walls/ceilings? Also best products how thick insulation needs to be and if re plasterboarding do we need to vapour barrier one?

Ceiling needs at least plaster skimming anyway and some plaster board inside cupboards have some water damage from leaks from old roof not sure if paint will cover but we are opening out for shelving.

There are 2 bedrooms (pics are of the slightly larger) and a small shower room too.

Any help appreciated Thankyou.

Here are the pics:

 

[foxhole]

Needs minimum 200 on top of existing or replace with 270-300mm of new .No vapour barrier required.

 

[Munnster1]

Thanks but I was meaning for the loft conversion ceiling and walls rather than the remaining storage cavity floor. I believe rigid insulation would be better but how thick and if necessary on all walls or just some or non at all? Basically wouldn't pass current building regs which obviously doesn't matter but would like to update for thermal efficency/heating costs if works out better than leaving. Do we need to rip it apart and redo?
Thankyou

 

[foxhole]

I used 100mm rigid between rafters and up walls all seams taped then overboarded with 40 mm insulated plasterboard .

My loft

• foxhole
• 3 Dec 2015
• 1

100mm insulation .

 

[Ian H]

100mm between rafters/studs in the walls, 150mm inbetween joists in the ceiling, then 50mm under the lot and finished with 12.5mm plaster board.

It’s very well thermally insulated but you can hear birds fart on the roof.