Extra loft insulation

[Jayab]

We'd like to improve the insulation in our loft (4" fibreglass wool at present between joists). The 'felt' under the interlocking concrete tiles is brittle/thick black bitumen type.

In the very cold weather we get condensation on this 'felt', which is not too bad.

I'd like to increase the insulation in the loft on top of the existing fibreglass but am wary of the accompanying condensation.

We have 6 or so vents at soffit level at both the front and back and the eaves are not restricted by insulation etc.

I've seen the wool based insulation at B&Q (55% Wool, 35% Recycled Plastic, 10% Binder.) which says breathable, which is encouraging. Would I need additional venting (e.g. ridge or midway up roof with tile vents?) though to prevent condensation increase?

I did try the bubblewrap/silver foil faced insulation pinned with correct gap to the pitch of the roof internally in the past but this caused a lot of condensation under the felt and had to be quickly removed. I followed the instructions correctly.

we have a 1970's semi.

thanks for any help!

 

[xr4x4]

Where are you putting or wanting to put the insulation?

 

[Jayab]

I want to top up the existing fibreglass wool insulation which sits between the joists ( probably run at right angles to the existing insulation).ie the 'floor' of the loft.

 

[HERTS P&D]

Should be minimum of 300mm thick. I did mine last year.

Makes a hell of a difference.

Andy

 

[FortJefferson]

We used 200mm Space Blanket at across the joists to top up. It's so easy to lay being covered in foil and plastic. The difference in incredeble.