Loft insulation advice needed please

[martyp]

Hi all,

I've just been told at B&Q I need more loft insulation and they have rolls for £5. I already have a layer of yellow fluffy stuff which I think is rockwool. I measured the height of th joists as 100mm, the existing insulation pretty much is the same depth as the joists.
Should I buy another roll and make is so that it is quite well compressed under the loft boards or is my current amount sufficient?
By comparison you really feel it colder sticking your head up in the loft compared to the rest of the house so I guess it's doing something.

Please can someone advise as I want to start putting boards down (would they help with insulation?)

 

[galliano2001]

martyp - its the air space within the mineral fibre that helps with the insulation, compressing it defeats the point of adding more. What they are suggesting is to lay extra rolls crossways to your existing setup to gibe you 200-250 mm of insulation.

If you want extra insulation and to board your loft then ideally you need to raise the height of your joists. Other solution would be to use a different insulation material that offers a better u value in the same space.

Ohh and yes loftboards will help a tiny bit.

 

[martyp]

Many thanks galliano2001. Much appreciated. The other thing I was thinking about is that foam that you can apply to the inside of the roof that would also insulate the loft space. I read that it can be sprayed on? Not sure if that would help at all or not?