Sorry for flogging a dead horse, however...
I have a suspended wood ground floor and will shortly have parquet laid on ply, around 50m2
Underfloor is 4x2 with about 4 inch to the subfloor, so could fit a max of 4inch insulation.
I had the idea to insulate and discussed it here after reading an article saying "netting and loft insulation is the wrong way to do it" https://www.diynot.com/diy/threads/floor-insulation-article.601960/
Using a few u value calculators, e.g. (https://www.rockwool.com/uk/resources-and-tools/tools/u-value-calculator/), and a p/m ratio of 0.36, 4inch of rockwool will get me a u value of around 0.03 Watt/mK
There's also the pain of pulling up the floor, compromising on the insulation thickness around the power cables etc.
A different thread https://www.diynot.com/diy/threads/10-or-12mm-pir-insulation-board.601978/ got me thinking.
10mm STS tile backer board https://www.sts-uk.com/tiling-preparation/professional-tile-backing-board is designed for flooring and has a thermal conductivity 0.034 Watt/mK.
Similar boards with the same u value are used for underfloor heating.
So if I am happy with gaining 10mm of floor height, laying these, then the ply will give the same u value as 100mm of rockwool.
Did I work that out correctly?
Is this a valid method for insulating the floor?
What am I missing
I have a suspended wood ground floor and will shortly have parquet laid on ply, around 50m2
Underfloor is 4x2 with about 4 inch to the subfloor, so could fit a max of 4inch insulation.
I had the idea to insulate and discussed it here after reading an article saying "netting and loft insulation is the wrong way to do it" https://www.diynot.com/diy/threads/floor-insulation-article.601960/
Using a few u value calculators, e.g. (https://www.rockwool.com/uk/resources-and-tools/tools/u-value-calculator/), and a p/m ratio of 0.36, 4inch of rockwool will get me a u value of around 0.03 Watt/mK
There's also the pain of pulling up the floor, compromising on the insulation thickness around the power cables etc.
A different thread https://www.diynot.com/diy/threads/10-or-12mm-pir-insulation-board.601978/ got me thinking.
10mm STS tile backer board https://www.sts-uk.com/tiling-preparation/professional-tile-backing-board is designed for flooring and has a thermal conductivity 0.034 Watt/mK.
Similar boards with the same u value are used for underfloor heating.
So if I am happy with gaining 10mm of floor height, laying these, then the ply will give the same u value as 100mm of rockwool.
Did I work that out correctly?
Is this a valid method for insulating the floor?
What am I missing