Sustainability Smarthome Health31 March 20261 min read
Why the meeting gets sleepy after forty minutes
It is almost never the agenda. It is the carbon dioxide, and it is measurable.
Outdoor air sits at roughly 420 parts per million of carbon dioxide. A closed room with four people in it passes 1000 ppm within the hour, and somewhere above that most people become measurably worse at concentrating, without ever noticing anything except that the room feels stuffy.
The reason this is worth a sensor rather than a rule of thumb is that the number moves faster than intuition. A room feels the same at 700 ppm and at 1600. Put a monitor on the shelf with a coloured ring and the household stops arguing about whether to open the window, because the answer is on the wall.
One caution when buying: many inexpensive monitors do not measure carbon dioxide at all. They measure volatile organic compounds and estimate a CO2-equivalent from them, which tracks cooking and cleaning products rather than people. If the specification does not say NDIR, it is an estimate.
Better insulation makes this more relevant, not less. An airtight house holds its heat beautifully and exchanges very little air on its own - which is why ventilation with heat recovery has stopped being a specialist product and started being the obvious companion to a well-sealed home.
