Advice for best insulation/floor system please

[garyo]

Only wandering slightly off topic, but there must be a point where the amount of cavity insulation you have becomes irrelevant given that the base of the inner leaf of the wall is sat on the earth. Is that concept ever expressed in documents? Obviously the shorter the building (bungalow!) the more pronounced the effect.

 

[r6deano]

Only wandering slightly off topic, but there must be a point where the amount of cavity insulation you have becomes irrelevant given that the base of the inner leaf of the wall is sat on the earth. Is that concept ever expressed in documents? Obviously the shorter the building (bungalow!) the more pronounced the effect.

I'm going to guess it's negligent in value, or perhaps it's a given constant, but if that were the case I would have thought it would have a value like Rsi and Rso in I values.

However I have been looking at blocks called Perinsul which help reduce the cold bridging you would normally expect from the cold slab transferring into the inner skin.

 

[John D v2.0]

Only wandering slightly off topic, but there must be a point where the amount of cavity insulation you have becomes irrelevant given that the base of the inner leaf of the wall is sat on the earth. Is that concept ever expressed in documents? Obviously the shorter the building (bungalow!) the more pronounced the effect.

Yes, that's basically a thermal bridge. It isn't essential to worry for a normal wall as the path to unheated space is quite long anyway, but you can get marmox insulated blocks which are strong but have a decent u value.
You can even get thermal breaks for structural steel if you have goal posts or something