Exteriors

Historically, exterior finishes were clays and sands with a finish coat of lime/sand/pigment plaster. The non-hydraulic lime plasters (calcium hydroxide) cure by absorbing carbon dioxide in the presence of moisture, turning back into limestone/marble (calcium carbonate).
Traditionally, on May Day in Europe, the wife would bring out the stored lime putty mixed with pigments (limewash), mix it up and brush it on the house. No "faux" finishes come close to the beauty/durability of a true limeplaster/limewash.
Lime plasters/washes have a unique property: they cure very slowly. If there is settling, earth or structural movements, the plasters' uncured lime heals the cracks by re-absorbing carbon dioxide--sealing any fissures. Wonder why ancient buildings last centuries or millennia? You now know why.

Hydraulic finishes cure by chemically bonding with water: cement, gypsum, and hydraulic limes. These finishes are less durable (<100 yrs), due to the fact that the sulfates are more water soluable. Combine these finishes with an impermeable paint, and you will inevitably trap moisture vapor, dissolving the substrate. This results in mold and efflorescence.

Even though lime is of high embodied energy, very little is needed, as the binder, mixed with water and mineral pigments-->limewash. It gets better with age, too, both in the stored product and the weathered finish. It slowly "chalks" off over the decades--quite unlike paint's catastrophic failure by cracking and peeling.

As a final limewash coat, I might add a few drops of hemp oil to provide a surface surfactant. Translation: a permeable water resistant finish. I use this finish sparingly, due to the fact that this hampers further limewashes. Philosophy: if it's a mineral substrate, stick with a mineral coating.