Interior insulation: cork or calcium silicate?

Hello,

I want to insulate the two exterior walls inside my office because the dew point is undershot in winter and condensation forms as a result. The temperature in the lower corners is about 3°C when it gets really cold outside. Otherwise, the walls are rainproof and I can exclude rising damp. Currently, there is wallpaper on them, slightly moldy in the corners, underneath there is filler, partly dispersion paint, plaster, and masonry.

I have imagined the renovation as follows: remove the wallpaper, remove flaking filler or paint, apply interior insulation, then plaster or fill it with suitable material.

My question: Should I use calcium silicate boards or cork? Cork is less permeable to water than calcium silicate... What advantages and disadvantages should be considered?

Thank you and best regards
joschi

Hello Joschi,

any weather, 3 degrees is little - I almost suspect you measured that at night, when the indoor air is below 16 degrees, right? I also suspect that something is bringing in more cold than usual there. But that plays little role in the choice of interior insulation.

I am always in favor of natural insulation materials as well. I do not know the moisture properties of cork. Important here are the moisture storage capacity and the capillary moisture transport properties. Maybe you can find out something from the supplier about that. Compare the values with proven interior insulation systems, like these:

Wood fiber, for example, has been proven for many years as interior insulation in connection with clay plaster. The two building materials score points because of their moisture storage capacity.

Calcium silicate, on the other hand, transports moisture very quickly and is not itself a breeding ground for mold; it is initially a basement renovation board (without much insulating effect) - the real insulation is then done by the succeeding products: lime-based boards with WLG 040 - 045 - also called "mineral interior insulation boards" (beware, do not confuse with mineral wool!)

These lime-based interior insulation boards (e.g., from KeimFarben, Ytong, Caparol, Sto....) are also plastered on the inside, and this interior plaster serves as a kind of vapor retarder. Make sure that you only use the plaster and adhesive mortar products that the manufacturer has tested (this is called: staying in the system).

I wish you much success

Susanne Junghans