Lowtech Graph lists low-tech options for every need of a home. Here you can compare them, find tutorials to build them, and link them together into a circular system. Why low-tech?
One of 2 ways to meet this need. Cost, carbon, footprint and rankings are relative to other solutions for the same need, not absolute.
Small ventilation units fitted in the wall of each room, one per room, instead of one central system with ducts. Each unit swaps stale air for fresh and passes the heat of the outgoing air to the incoming air. Rooms get fresh air without losing their warmth, and a faulty unit is easy to repair or replace.
Build it
This solution is not buildable as a DIY project.
Cost
Medium
Upkeep
Seasonal
Skill to build
Intermediate
Lifespan
15-25 years for the core unit; filters need replacement every 3-6 months, same profile as central MVHR
Embodied carbon
Medium
Space / material use
Low
Output timing
On-demand/controllable
Skill to repair
Intermediate
Regulation (FR example)
Dwellings must have general and permanent ventilation (arrete du 24 mars 1982, modifie). Mechanical ventilation is the usual way of meeting it in an airtight building.
Levels are relative to the other options for this need, not absolute. Fewer dots is lighter.
Decentralised single-room heat-recovery ventilators (This page) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Medium · Skill to build: Intermediate · Upkeep: Heavy · Change to daily life: None · Works without the grid: No Choose it if you want heat-recovery ventilation room by room, without running ducts.
Mechanical ventilation with heat recovery (MVHR) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Medium · Skill to build: Intermediate · Upkeep: Heavy · Change to daily life: None · Works without the grid: No Choose it if you want the whole house ventilated by one central unit that keeps most of the heat.
We don’t list sizing or quantities, as the yield of each technique depends on the quality of its build. The catalogue compares options but doesn’t dimension them. Regulatory notes are indicative, with a French example, and need to be confirmed locally.