Passive
One of 4 ways to meet this need. Cost, carbon, footprint and rankings are relative to other solutions for the same need, not absolute.
Floor area for the alcove and enough headroom to sit up in it. Nothing is fixed to the building's structure, which is what puts it within reach of a tenant as well as an owner
An enclosed sleeping alcove, closed off by a curtain in cold weather, so what has to be kept warm at night is the bed rather than the room. It is the oldest version of the move this sub-function otherwise makes with hot water bottles and heated tables -- warm the person, not the air -- and the only one that needs no heat source at all: the enclosure simply holds the sleeper's own output in a volume small enough for it to register. In a small flat that changes the arithmetic of the whole night, because the alternative is heating every room to sleep in one. The build this comes from reports two effects that are not thermal at all, total darkness and near-silence, as the ones the occupants actually noticed.
none
Compare building and maintaining complexity, as well as efficiency where possible.
| Solution | Build skill | Upkeep burden | Efficiency |
|---|---|---|---|
| Hot water bottle | None | 2 | N/A |
| Electrically heated table (kotatsu) | Basic | 4 | N/A |
| Solar-powered foot stove (heat cube) | Intermediate | 3 | N/A |
| Box-bed with thermal curtain | Intermediate | 0 | N/A |
Build skill and upkeep burden are proxies (lower burden = simpler to maintain); the efficiency column is this sub-function’s ranking, 1 = best. “N/A” where an axis isn’t rated here.
No sizing or quantities: how much a technique yields, and how much a household needs, both depend on the build and the people, so the catalogue compares options rather than dimensioning them. It carries no bill of materials and no build sequence, and it is written for an oceanic, clay-soil climate (Normandy, France). Regulatory notes are indicative and need confirming locally.