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?
Attic radiant barrier
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
An accessible roof space with room for an air gap in front of the foil. The source is explicit that where summer heat gain through the attic is small the benefit shrinks with it, which is the case in a mild oceanic summer.
A shiny foil fixed under the roof, facing an air gap. It turns back the heat that a hot roof radiates downward, so less reaches the insulation and the rooms. It keeps the top floor cooler in summer. It only works facing a gap, and it is not insulation.
Indefinite where it faces an air gap; laid flat on insulation it silts up with dust and stops reflecting, which is why that position is not recommended
Levels are relative to the other options for this need, not absolute. Fewer dots is lighter.
Attic radiant barrier (This page) 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.
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.
Vented roof / attic assembly 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.
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.