We have a bungalow with a suspended floor as its on a slope. Its got enough room under the house to work running pipes etc and insulating floors from below.
My views on concrete block is that they are totally energy inefficient as the blockwork conducts cold so easily. Although we have a double wall with cavity my view is the internal wall which runs below floor level is subject to extreme cold in the void under the building and this then comes up through the wall. I have had to internally insulate which has worked on all external walls. However there is one internal supporting wall that I haven't done and its very cold.
My point is isn't this method of building so energy inefficient it shouldn't be used?
If the intenal wall was timber framed with insualtioin inbetween the timbers this would be much more efficient?

Am I being naive?

No but you are talking about designed in thermal bridging, poor, it also happens on gable walls and chimneys.

Needs mitigating and our whole building design needs rethinking

Sometimes possible.

Also one can build on an insulated raft

Design out thermal bridging

Posted By: converseI'd have no hesitation using reclaimed block though.

Can you get reclaimed blocks with strength certification? I wouldn't want to build a wall using uncertified/untested blocks.

There are various 'low carbon' blocks available, such as those from Lignacite. No connection; never used any etc.