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?
Night-flush cooling
Passive
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 climate with a real day/night temperature swing and openings that can be safely left open overnight
Opening the house wide on summer nights to let cool air flow through, then closing it in the morning. The cool night air chills the walls and floors, and they keep the rooms cool through the next day. It needs no power, only windows placed for the air to cross.
Levels are relative to the other options for this need, not absolute. Fewer dots is lighter.
Night-flush cooling (This page) 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.
Whole-house fan 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.
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.