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?
Vented roof / attic assembly
Passive
One of 7 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 roof built with a ventilable space, soffits that can take an inlet, and a ridge or upper outlet. The source recommends the opposite, an unvented assembly, where wind-driven rain or wildfire embers are a real risk, since the same openings let those in.
Vents low at the eaves and high at the ridge, so air flows through the roof space. The moving air carries away heat that builds up under the roof, and the damp that would otherwise condense there. The rooms below stay cooler and the roof timbers stay dry.
Levels are relative to the other options for this need, not absolute. Fewer dots is lighter.
Vented roof / attic assembly (This page) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Intermediate · Upkeep: Light · Change to daily life: None · Works without the grid: Yes Choose it if you want the roof space to shed its heat and its damp, and the timbers to stay dry.
Fixed horizontal overhangs (south) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: None · Upkeep: None · Change to daily life: None · Works without the grid: Yes Choose it if you want south windows shaded in summer and sunny in winter, with nothing to adjust.
Adjustable brise-soleil / shutters (east-west) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Medium · Skill to build: Basic · Upkeep: Regular · Change to daily life: Daily · Works without the grid: Yes Choose it if you want to stop the low morning or evening sun on east and west windows.
Deciduous vegetation shading Can I use it? Not 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: Yes Choose it if you want summer shade and winter sun that cost nothing and grow by themselves.
DIY shade-sail window screen 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 you want the cheapest outside shade for a window, sewn yourself.
Cool (high-reflectance) roof surface Can I use it? Not 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 you want cooler rooms under a sunny roof, from a coating you can make yourself and wash off before winter.
Attic radiant barrier Can I use it? Not in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Basic · Upkeep: None · Change to daily life: None · Works without the grid: Yes Choose it if you want a cooler top floor for the price of a foil under the roof.
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.