Loft insulation - 95mm joists

[ldoodle]

Hi,

As title, loft joists are 95mm finished dimension.

It's part boarded with 1 layer of thin fibre glass roll sitting on the ceiling below at the moment so looking to swap it all. My loft is already shallow pitch and have services up there which would make loft legs or similar a no (to get thicker insulation for example).

What's the right method? Still need a gap between face of insulation and underside of boards?
It seems the FleeceWool type stuff comes in 75mm or 100mm thickness, so first question is crucial! If no gap required would 100m slightly compressed be better?

Thanks

 

[flameport]

100mm between with 200mm in the opposite direction on top. No gaps.

100mm of loft insulation on it's own will be totally inadequate.
If there isn't enough space to install loft legs or whatever, then the loft can't be used for storage.

 

[ldoodle]

If there isn't enough space to install loft legs or whatever, then the loft can't be used for storage.

Why? Been used for storage since I've been in it - nearly 10 years.

100mm of loft insulation on it's own will be totally inadequate.

But it will surely be better than nothing or even what I have at the moment. My boiler is up there and is already at the minimum clearance below for servicing.

 

[flameport]

You can store whatever you want there, but 100mm of insulation is far below the minimum and will result in significantly larger heating bills every year.

It's better than no insulation, but not by much. The minimum is 270mm, more is desirable.

 

[ldoodle]

Yeah I get that, and have seen the 270mm recommendation. But I'm not going to re-pitch my roof (which would require the neighbours to do the same as it's a semi) to be able to move the boiler up (the flue is already as close to the apex as possible) to be able to raise the floor to accommodate more insulation. A few hundred pound job into many thousands (possibly tens) would make ROI completely unobtainable.

In the mornings at the moment downstairs is about 17 degrees and upstairs is less than 10. With no heating on. Looking at how to (realistically) reduce that difference.