Hello all, first time poster long time lurker.

We have an older home built in the early 1900's. We would like to insulate the basement to help with our energy bills, especially in the winter time. However, the basement has these clay or terracotta type blocks, not your typical cement blocks like today's construction. The blocks are slightly uneven so the walls are not perfectly flat. The basement walls are always dry and we have no current issues with mold.

From my research, its seems the best way to properly insulate basements is to attach the blue foam board to the walls and reduce the gaps between the wall and foam board as much as possible to reduce moisture buildup. Since these walls are uneven, we would have lots of gaps. My biggest concern is creating an environment for mold to grow if the blocks were to ever have moisture on them.

Below are a few photos of the walls. The first one is the interior wall itself. The second one is one of the blocks cut in half. The third one is an outdoor view of the block.

My questions are:

1. What is the name of this type of block?

2. Is spray foam insulation the best choice for this type of wall?

3. For which ever type of insulation we install, do we need to prep the walls with any moisture barrier (physical or spray on product) even though the walls are dry?

Any help or opinions would be appreciated.