Attic insulation 300 much better than 150mm?

micks_address

Hi folks,
Have 150mm of insulation in attic and was going to throw down some flooring on top to make storage easier. Is it worth putting in extra to bring level to 300mm? Will have to raise joist level to floor so more expensive.. Just. Wondering will I notice the extra insulation?
Thanks,
Mick

fred funk }{

Yes, definitely. Just make sure you don't squash it down as it becomes ineffective.

Calibos

I've read that something like 80-90% of the Heat Loss prevention comes from the first 150mm of loft insulation and its diminishing returns after that.

https://www.thegreenage.co.uk/what-is-the-recommended-thickness-of-loft-insulation/

I personally wouldn't bother adding anymore unless I wanted to floor the attic for storage and would use the Insulation Foam backed Loft floor panels which would give me my floor, add a little bit more to the insulation values while nowhere near the hassle of adding those joist stilts to raise the loft floor to accommodate more insulation roll and losing a lot of attic height in the process.

bunderoon

Renovating our house, we had existing 4x1s which I layed 100mm and then 'cross battened' it with 6x1s and layed 200mm. The difference was very noticeable. Well worth it, even if it may be the first 200mm that makes the most difference.
Then floored on top of the 6x1s with 20mm chipboard.

Be careful of any long spans. Support the new runs at the top of the internal block walls. You dont want cracked ceilings.

micks_address

Calibos wrote: »

I've read that something like 80-90% of the Heat Loss prevention comes from the first 150mm of loft insulation and its diminishing returns after that.

https://www.thegreenage.co.uk/what-is-the-recommended-thickness-of-loft-insulation/

I personally wouldn't bother adding anymore unless I wanted to floor the attic for storage and would use the Insulation Foam backed Loft floor panels which would give me my floor, add a little bit more to the insulation values while nowhere near the hassle of adding those joist stilts to raise the loft floor to accommodate more insulation roll and losing a lot of attic height in the process.

Thanks, the 'easiest option' would be to go with 150mm and then add foam backed boards so we could use for storage... have feeling the foamed back board would be expensive? Adding depth on existing joists to allow 300mm seems a lot of work

Calahonda52

Calibos wrote: »

I've read that something like 80-90% of the Heat Loss prevention comes from the first 150mm of loft insulation and its diminishing returns after that.

https://www.thegreenage.co.uk/what-is-the-recommended-thickness-of-loft-insulation/

I personally wouldn't bother adding anymore unless I wanted to floor the attic for storage and would use the Insulation Foam backed Loft floor panels which would give me my floor, add a little bit more to the insulation values while nowhere near the hassle of adding those joist stilts to raise the loft floor to accommodate more insulation roll and losing a lot of attic height in the process.

This is the wrong answer unless, and its a big unless, the existing insulation will sit tight against the underside of the rigid insulation, and iff, the air flow from the eaves is directed up above the glass fibre via ventilation baffles fitted at the eaves.

micks_address wrote: »

Thanks, the 'easiest option' would be to go with 150mm and then add foam backed boards so we could use for storage... have feeling the foamed back board would be expensive? Adding depth on existing joists to allow 300mm seems a lot of work

The alternative is to add 2" by 2" timbers on top of existing rafters, screwed with 4" screws and add what ever depth you want: [2/4/6/8/10]" etc

Also ensure power cables have room to cool to air: normal ducted.
I then used cellulose, which is non toxic and fills all nooks and crannies

micks_address

Calahonda52 wrote: »

Calibos wrote: »

I've read that something like 80-90% of the Heat Loss prevention comes from the first 150mm of loft insulation and its diminishing returns after that.

https://www.thegreenage.co.uk/what-is-the-recommended-thickness-of-loft-insulation/

I personally wouldn't bother adding anymore unless I wanted to floor the attic for storage and would use the Insulation Foam backed Loft floor panels which would give me my floor, add a little bit more to the insulation values while nowhere near the hassle of adding those joist stilts to raise the loft floor to accommodate more insulation roll and losing a lot of attic height in the process.

This is the wrong answer unless, and its a big unless, the existing insulation will sit tight against the underside of the rigid insulation, and iff, the air flow from the eaves is directed up above the glass fibre via ventilation baffles fitted at the eaves.

micks_address wrote: »

Thanks, the 'easiest option' would be to go with 150mm and then add foam backed boards so we could use for storage... have feeling the foamed back board would be expensive? Adding depth on existing joists to allow 300mm seems a lot of work

The alternative is to add 2" by 2" timbers on top of existing rafters, screwed with 4" screws and add what ever depth you want: [2/4/6/8/10]" etc

Also ensure power cables have room to cool to air: normal ducted.
I then used cellulose, which is non toxic and fills all nooks and crannies

are you an insulator professional? can I pm you?