I could never understand why they haven't really caught on in the UK. They have been used in Germany for decades. Building is quick, they have good load bearing qualities, and the only reason I can think of why they are not more commonplace is IMO our love of cavity wall construction, with a brick finish.

HowardJ

I have looked into these some years ago and they were quite expensive.

I discussed them with NBT last week, and they are hoping to bring the costs down when they manage to get a UK production plant online. This is unlikely to occur until the end of 2013 at the earliest.

When comparing prices don't forget the much reduced labour cost between the UK convention of cavity wall and the cost of putting up the porotherm blocks.
As a thought from your first post above if you are planning PH or near that, then the porotherm as you suggest will need EWI to get to the insulation level required, would it be possible to use solid blocks say 180 or 200 thick (what ever the building regs demand for structural stability) plus EWI to the required level of insulation. This I would have thought would be much cheaper than porotherm.
The advantage of porotherm type blocks is
1 the insulation value due to their construction method (air spaces plus length of heat path)
2 speed and ease of building.
If the porotherm don't give the insulation needed and extra EWI is required then why pay for that (expensive) insulation feature when solid blocks plus a bit thicker EWI will do the same thing.

Posted By: HOWARDJDo like the speed of construction for clay blocks though.Also they don't need to dry out.

Not my area of interest at all. But google for "thin joint blocks" shows there are several other types of block that may offer speed and quick-drying joints. No idea about price.