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?
Secondary glazing (retrofit inner pane)
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.
Traps a still-air layer against an existing window instead of replacing the window. The considered version is a second pane held in a frame inside the reveal, in acrylic, polycarbonate or film, which keeps the view. The crude version is bubble wrap misted onto the glass, which costs almost nothing, goes up in minutes and gives up the view, so it suits a window nobody looks through. Same physics either way: the gain is the trapped air, not the material.
20-30 years, same sealed/hardware failure modes as primary glazing
Embodied carbon
Low
Space / material use
Low
Output timing
None
Skill to repair
Basic
Regulation (FR example)
Changing the external appearance of an existing building normally requires a prior declaration (declaration prealable) at the mairie; stricter rules and an architect consultation apply within a protected or heritage perimeter.
Levels are relative to the other options for this need, not absolute. Fewer dots is lighter.
Secondary glazing (retrofit inner pane) (This page) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: None · Upkeep: Light · Change to daily life: Daily · Works without the grid: Yes Choose it if you rent, or must keep your old windows, and want a cheap extra layer.
Triple-glazed, low-E windows Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: High · Skill to build: Intermediate · Upkeep: None · Change to daily life: None · Works without the grid: Yes Choose it if you want the windows that keep the most heat in.
Double-glazed windows, insulated frames Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Medium · Skill to build: Intermediate · Upkeep: None · Change to daily life: None · Works without the grid: Yes Choose it if you want most of the gain of new windows for a lower price and weight.
Insulated operable shutters Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Basic · Upkeep: Regular · Change to daily life: Daily · Works without the grid: Yes Choose it if you want the strongest night-time insulation over the glass for little money.
Electrochromic (smart) glazing Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: High · Skill to build: Specialist · Upkeep: None · Change to daily life: None · Works without the grid: No Choose it if you want each window to let the sun in or keep it out at the touch of a switch.
Insulated draft-blocking curtains 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: Yes Choose it if you want to stop draughts at the window with something you can sew yourself.
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.