Early houses were insulated with thick masonry walls, which restrict energy loss by conduction because k is relatively low. The large thickness L also decreases energy loss by conduction, as shown by energy transfer equation. There are much better insulating materials, however, and layering is also helpful. Despite the low thermal conductivity of masonry, the amount of energy lost is still rather large, enough to raise the temperature of 600 kg of water by more than 1°C.

True or False: Materials having high thermal conductivities provide better insulation than materials having low thermal conductivities.

1.) True. The rate of heat flow in a material is proportional to its thermal conductivity.
2.) False. A good insulator transfers energy by heat effectively, and has low thermal conductivity.
3.) False. A good insulator does not transfer energy by heat readily through it, and has low thermal conductivity.
4.) True. Thermal conductivity measures a material's usefulness as heat insulation.

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