ᐅ Hollow clay brick or brick filled with wood fibers

Hello, we are currently considering which option is better. Some construction companies advise against the insulated blocks due to concerns about mold growth ??? We would only not be able to achieve a KfW 40+ house because of the bricks. Could you share your experiences with us? Thank you

Neither option is ideal. Using unfilled blocks is really poor quality, although it is still commonly done.

Use blocks filled with perlite or mineral wool. These offer the best properties.

Alternatively, consider calcium silicate blocks plus an external thermal insulation composite system (ETICS) / external wall insulation (EWI).

Depending on the insulation material, no water should enter the blocks during construction, meaning they must be protected from rain. Sometimes the insulation seems to settle downward, which undermines its effectiveness.

If the issue is "just with the wall," recalculating might help. Initially, we planned only for KfW55, but with the photovoltaic system and the 40cm (16 inches) Ytong blocks, we are close enough that only a little extra insulation is needed on the foundation slab to meet KfW40 standards. In practice, this probably won't make much difference, but since the photovoltaic system was already planned, we are able to receive good subsidies for the battery storage.

WilderSueden schrieb:

Depending on the filling, no water should enter the bricks during construction, meaning they must not be exposed to rain. Sometimes the filling seems to slip downward, which undermines its purpose.

If it’s "just against the wall," recalculating might help. Initially, we only planned for KfW55, but with the photovoltaic system and the 40 cm (16 inches) Ytong blocks, we are close to meeting KfW40 standards. Only a bit more insulation on the ground slab is needed. In practice, this will probably not make much difference, but the photovoltaic system was planned anyway, so we are getting good subsidies for the storage system.

Our energy consultant says something different than the consultant from the brick manufacturer yesterday. According to the brick manufacturer, the wood does not absorb moisture!? That was exactly my concern, about moisture and the filling slipping downward.

Bookstar schrieb:

Both options are not ideal. Unfilled material is really poor, even though it is still often used.

Choose either perlite-filled or mineral wool-filled. These offer the best properties.

Alternatively, calcium silicate blocks plus external thermal insulation composite system (ETICS).

What is wrong with the wood fibers?

Basically nothing, I’m a big fan of wood fibers. However, I do have concerns about moisture. With perlite, you don’t have that issue because it is hydrophobized.

Also, wood fiber in bricks has not been tested extensively yet, while perlite has been used for a very long time with excellent results.

Perlite is mineral-based, and mineral in mineral appeals to me more.