Insulation + flooring in attic

Dublimax

Looking to insulate and floor the attic for storage purposes.
There is already insulation between the joist but it looks in bad shape so I want to remove it, put new one and chipboard on top.

The attic is as follow:
Gable roof
5m*3.2m with top height 0.94m
joists are 100mm deep.
joists are not all the same between 35/40mm width and joist centres are 290/330mm

Few questions:

There are 4 ceiling light in the landing with wiring in the attic. If those are replaced by LED lights I should be able to lay insulation over them?

All wiring can be covered with insulation but the heavy ones for power shower?

If I am correct putting 170 or 200mm glass mineral wool in between the joists and squeeze it with the chipboard isn't the best as compressed insulation is not as effective and there is also a risk of cracking the ceiling. So I plan on putting 100mm glass mineral wool (can I put 120 or 150mm and slightly compresse it?).

100mm seems like it is not enough though. However since the max height is only 0.94m I am a bit reluctant to add an extra 200mm on top of it. I can add the extra 200mm where I am not flooring but what about the rest?

In case I were to add an extra layer on top of the 100mm (let's say I add 50mm) what's the best way to fix the chipboard to the joists then?

Thanks

dathi

you could try some thing like this http://www.eurofloor.ie/ 100mm fiber between the joists and then walkway insulation boards for the area you want for storage 300mm everywhere else

vertico

Put 100mm between the joists. Sheet the area you want floored with 50mm kingspan and cover with attic flooring(comes in 2.4 / .600). Roll another 200 insulation across the remaining attic space. Job done

Dublimax

dathi wrote: »

you could try some thing like this .... 100mm fiber between the joists and then walkway insulation boards for the area you want for storage 300mm everywhere else

I was thinking about these as they have similar ones in bnq. Might be a dear option as the ones in bnq are 40€/m^2

vertico wrote: »

Put 100mm between the joists. Sheet the area you want floored with 50mm kingspan and cover with attic flooring(comes in 2.4 / .600). Roll another 200 insulation across the remaining attic space. Job done

Good idea. How do you fix the attic flooring over the kingspan? Or do you just leave it loose?


I was also considering making ~100mm perpendicular timber legs accross the joists, fill that with glass mineral wool and then floor it.

I also saw these dial loft storage stilts in bnq that would give me another 150mm where I want to floor.

vertico

Fix the flooring by screwing trough the insulation to the joist, also split the insulation 1st down the middle to make easy access to the attic. I've done it loads of times it's fairly straightforward to do.
Also notch any wires into the rafters or raise with lats

gutteruu

I just floored a huge attic that had wool well above joists. I ran in 2x4's perpendicular and floored on top. Assuming your ok with losing head height. Makes it easy for cables/wires running over joists and gives easy access in case of issues also.

vertico

gutteruu wrote: »

I just floored a huge attic that had wool well above joists. I ran in 2x4's perpendicular and floored on top. Assuming your ok with losing head height. Makes it easy for cables/wires running over joists and gives easy access in case of issues also.

I've done the same, once there's enough head room

gutteruu

vertico wrote: »

I've done the same, once there's enough head room

I only did it because the insulation was already there and they are going to need access to sky cables etc in future. For OP's sake, vertico's way is best practice and the way I would do it in my own house, if cables/pipes/ducting allows. Cost difference is negligable and gives better U value and better support.

Dublimax

Any recommendation on the Kingspan to use? Should I go with foiled sheet to radiate heat?
Thanks

vertico

Foiled 50mm is perfect,,80/90mm screws and Mark the sheet where the wires are,, you don't wanna hit any ,

dathi

vertico wrote: »

Foiled 50mm is perfect,,80/90mm screws and Mark the sheet where the wires are,, you don't wanna hit any ,

50mm kingspan plus 100 fiber will give you a u value of 0.21 part l of the building regs require you to have a u value of 0.16 for refurbishment work in order to hit the 0.16 target you would need 80mm of kingspan

gutteruu

dathi wrote: »

50mm kingspan plus 100 fiber will give you a u value of 0.21 part l of the building regs require you to have a u value of 0.16 for refurbishment work in order to hit the 0.16 target you would need 80mm of kingspan

Just out of interest how much of a difference to the u-value would 18mm of ply flooring add? I was told in the past it has pretty decent insulation properties?

dathi

gutteruu wrote: »

Just out of interest how much of a difference to the u-value would 18mm of ply flooring add? I was told in the past it has pretty decent insulation properties?

0.16 was with 100mm fiber 80mm kingspan and 18mm osb if you leave out the osb it becomes 0.17 so there is a difference of 0.01 in the u value .