I guess you found different descriptions because there were different things done, depending on the order/rule of the house. In some monasteries it might have been used as a kitchen. A book about Inchmahome Priory in the lake of Menteith, Scotland, says:

“The calefactory, or warming house, with its large double fireplace occupies much of the rest of the east range’s ground floor. This was the only room where the canons were permitted to warm themselves in cold weather. It has also a sink, or slop basin, with a drain in its east wall, suggesting that the room may despite its unusual position, have served as a kitchen. [...] It may even be that the kitchen belongs to ta later house conversion made when monastic life ceased around 1560.”

I’ve never seen this use of a warming house before. But then – I’m not really a specialist. The warming houses I’ve seen were constituted around a dominating fireplace.

A room like that was used as a scriptorum? Seems a bit odd, because that would mean relatively big windows.

As for the calefactory, I’ve read a few different things. Most sources refer to it as just a heated sitting room, but others describe it as a working room, particularly for noisy activities. One even describes a particular calefactory that was used as a scriptorium, where manuscripts were copied, although I haven’t seen others described in that way.

The plan is to have tables and benches, as you say. As for the heat source, we were going to have a typical wall fireplace, but since we already have two others in separate locations, there was some preference for a different appearance for more variety, even if it’s a design that would be unusual in that setting.

That said, there are some historic drawings that depict medieval Italian kitchen firepits that are somewhat similar.

A calefactory usually has a big fireplace embedded in one wall, tables, and benches. Back then it was the only part of an abbey that was heated, so the monks gathered there in there “off-duty” time. The dormitories were usually located right above it, so they would be warm at night.

The stove you put in the room surely looks nice. But I’ve never seen any historic abbey with a thing like that. But I doubt that anyone would care about that

English’s obviously not my native language – so please excuse any mistakes.