I have one, overriding mantra here – Breathability.
Paints, wherever they are to be used, need to be totally breathable. Old houses need to breathe – so does the timber they are built with – the window frames, the door frames, the walls, the render..
In short, there are two main paints that we use – those for walls are either lime based – limewashes, or clay based – clay paints. On joinery, we use linseed based paints – although there are modern clay paints which are almost as breathable, and still give good coverage. Linseed paints last for many years, and just need freshening up every 5 years or so with a thin coat of linseed oil. The paint never cracks, and the wood never rots, because no moisture is trapped into it.
DO NOT ever use plastic paints – acrylic paints – modern ‘breathable’ paints… The big paint companies will tell you their paints are ‘breathable’ – their paint chemists tell me they are anything but… Judge for yourself – put a nice coat of Dulux gloss all over your windows and see how long it is before it all cracks and flakes, rotting the timber underneath by trapping moisture.. It’s not breathable and never will be – its made with plastic!