ᐅ Instead of insulation, construct a second brick wall.

A comprehensive insulation system is planned for our house. Currently, we have a 25cm (10 inches) brick wall, partially still in shell construction, otherwise covered with lime plaster. Naturally, a thick layer of insulation is necessary. We are now considering, instead of the common and cheapest polystyrene insulation, to build a second 25cm (10 inches) clay brick wall, possibly with a 5cm (2 inches) mineral wool insulation or another material in the cavity between the walls. Has anyone had experience with this construction method and can share any potential disadvantages?

Well, it’s hard to say. Clay walls alone don’t provide much insulation, but they do have the charm of being essentially single-layered!

When it comes to external insulation, careful planning is necessary because the house might become too airtight, which could lead to considering a ventilation system.

At first glance, cavity insulation seems like the most practical option. Maybe even clay walls plus cavity insulation plus a breathable membrane could be a solution?

Hello Blurboy! Thanks for your response. Actually, we planned for the house to be plastered. Brick façades are not very common in our region (Upper Austria). For the bricks, we would choose one with air chambers, which are commonly offered, for example by Wienerberger or the Senftenbacher Bio 25 VZ. These would be installed using Dry-Fix or thin-bed mortar. The advantage is that the time-consuming task of mixing mortar is eliminated, which would significantly simplify the process.

Hello,

Baurausch schrieb:
...Now we are considering, instead of the usual and cheapest polystyrene insulation, to build a second 25cm (10 inch) clay brick wall, possibly with 5cm (2 inch) stone wool insulation or something else in between.

What a waste of effort. It hardly improves the energy efficiency.

Best regards