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?
Whole-house fan
Needs the grid
One of 6 ways to meet this need. Cost, carbon, footprint and rankings are relative to other solutions for the same need, not absolute.
What your site needs
A ventilated roof space big enough to take the air it moves, windows that open, and outdoor air that actually goes cold at night. It also needs an insulated shutter, or the opening it cuts through the ceiling leaks heat all winter.
A large fan in the ceiling that pulls cool night air in through open windows and pushes the day’s hot air out through the roof space. Night-flush cooling done by machine rather than by opening the right windows, which makes it work on still nights when the passive version does not.
Build it
This solution is not buildable as a DIY project.
Cost
Medium
Upkeep
Occasional
Skill to build
Intermediate
Lifespan
Long, given a motor that can be serviced and a shutter that still closes
Levels are relative to the other options for this need, not absolute. Fewer dots is lighter.
Whole-house fan (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: Light · Change to daily life: Occasional · Works without the grid: No Choose it if you want night cooling that works even on still nights.
Night-flush cooling Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Basic · Upkeep: Light · Change to daily life: Daily · Works without the grid: Yes Choose it if your nights are cool and you want to cool the house for free.
Evaporative cooling Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Basic · Upkeep: Light · Change to daily life: Occasional · Works without the grid: Yes Choose it if your summers are dry and you want cheap cooling.
Heat pump (air- or ground-source), reversible mode Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: High · Skill to build: Specialist · Upkeep: Heavy · Change to daily life: None · Works without the grid: No Choose it if you already need a heat pump for winter and want the same machine to cool.
Night-sky radiative cooling Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Medium · Skill to build: Intermediate · Upkeep: Light · Change to daily life: None · Works without the grid: No Choose it if your summer nights are usually clear and you want to cool with the night sky.
Ceiling fan Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Basic · Upkeep: Light · Change to daily life: None · Works without the grid: No Choose it if you want to feel cooler where you sit, for a fraction of a cooling machine’s power.
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.