Loft insulation OVER existing boards

[kjacko]

Hi,
My mum is 81 and lives on her own in a bungalow (bear this in mind later ).
She has just had a completely new roof as it was EOL with holes and leaks.
Her loft is boarded out with minimum insulation and I wanted to bolster this by rolling out 200mm insulation just over the top of the boards, rather than take all the boards up and then raise them over the insulation.
The loft is empty and mum will never go up there so I see no need to lift the boards.

Are there any cons to doing it this way?

 

[robinbanks]

No cons I can think of in your scenario. If you might want storage in future using rigid board insulation in the centre would mean you could just put down hardboard and walk on it. 125mm PIR is approx equivalent to 200mm wool (but it depends on the U value of the wool)

Strive to retain eaves ventilation while rolling out to the edge

 

[kjacko]

No

Strive to retain eaves ventilation while rolling out to the edge

So, are you. Saying NO to there being any cons, or NO it shouldn’t be rolled on top of existing boards?

 

[kjacko]

Also, is it a matter of “well any extra insulation helps”, or is it “unless it’s done right it will not provide any benefit”?

 

[robinbanks]

I'd consider wool round the edge and board in the middle; wool is easier to install in fiddly areas. Board retains the usefulness of the loft, but if you want to wool it all out crack on

Insulation needs to be done right to be of benefit. I'm assuming the existing wool is touching the underside of the boarding out and hence not an airflow path. If it is not, and cold air can flow between wool and board, then insulating on top of the board is less effective. The simple solution to that would be to ensure air cannot flow under the boards by blocking the edges with a fillet of wool, or ensuring the overlapping wool bridges from the non boarded areas to the boards without a gap