a Ziegel block
Ziegel hollow core clay blocks are commonly used in many EU countries and are beginning to make inroads here. While the sq.m. cost of the materials is similar to conventional walling in the UK there are several major advantages:
- The speed of building is greatly increased
- There is very little water involved (about 5% compared with traditional brickwork) so drying out times are drastically cut
- The insulation values are much better (although for really good insulation values such as with the Passivhaus standard they will require extra insulation adding either internally or externally
They can be used either as a single skin or with cavity wall.
There is a Porotherm U-Value Indicator which gives values for different wall types
Bouyer Leroux are a French firm doing this type of block. In the UK the company NBT (Natural Building Technologies) use Thermoplan Ziegel blocks
Here are a couple of videos showing how these blocks are used with very narrow mortar beds.