The most effective treatment would have been gassing the whole house. This is the solution that I pushed for, but the exterminators were worried about the proximity of the next door neighbors. Strictly according to the law, their house is far enough away but our neighbors are old and like to wander into our garden in our absence, so the exterminator was worried about their overall safety.
The next best method is to drill holes into all the wooden beams, inject them with a poisonous resin, and re-impregnate all wood in the house. It looks like this:
Luckily for us, our beams are exposed. If not, the ceilings would have had to be removed. This process isn’t an instant kill of the woodworm. Any worms die upon reaching the resin and if any make their way out, they will most likely not re-infect due to the impregnation. In one particular beam that showed no signs of infestation, the worms were clearly crunching away. Now all sounds in that beam have stopped. In other places, I can still hear them. It’s quite unsettling.
Additionally, the extermination team gave the barn a spray. The chemicals are available over-the-counter, so to speak, but I am not comfortable using toxic substances myself. They had all the protective clothing and masks and a power sprayer thingy so it was much better that they did it and we just paid for it.
I hope that'll be the end of the woodworm story.
Do you feel itchy?
*Polish equivalent to crossing your fingers for good luck.