Insulation and Saving Energy: Concept Map

Concept Map

Organise the vocabulary, quantities and relationships into a connected model.

This extension applies that lens specifically to Insulation and Saving Energy.

Insulation is any material or design used to slow unwanted heat transfer. It does not create warmth and it does not create cold — it simply makes the journey harder for heat.

The secret ingredient in almost every good insulator is trapped air. Still air is a very poor conductor, so a material full of small pockets of trapped air — wool, polystyrene, glass fibre, feathers, shredded paper — slows conduction badly, and because the air is trapped it cannot set up convection currents either.

That is why a fluffy jersey is warmer than a thin one made of the same wool: it holds more air, not more wool.

Insulation in a South African home:

• Ceiling insulation under a corrugated iron roof — the single biggest improvement in most houses. It keeps heat out in a Limpopo summer and in on a Highveld winter night.
• A geyser blanket wrapped around the hot water cylinder, so the water stays hot for longer between heating cycles.
• A hotbox (wonderbag) — a cushion-stuffed bag that a pot is placed into. Bring samp and beans to the boil for a few minutes, switch off the plate, seal the pot in the hotbox, and it goes on cooking for hours on stored heat. During load-shedding it is the difference between a cooked supper and a cold one.
• A lid on the pot, closed curtains at night, and filling a kettle only as far as you need.

Worked example. A pot at 95 °C is sealed in a hotbox and loses about 4 °C per hour. After 5 hours it has lost $4 \times 5 = 20$ °C, so its temperature is $95 - 20 = 75$ °C — still hot enough to serve. On an open counter the same pot would have been cold long before.