Improvements to chimney flues occupied many scientific minds.
The simplest was the fireback, a decorated slab of cast iron placed at the rear of the firebox to retain and radiate heat.
Hot-water pipes embedded in the floor, generally set in concrete, became popular after World War II, particularly for slab-on-grade houses.
Radiant heat provides a comfortable, encompassing warmth, as opposed to the fixed-point heat of radiators and hot-air registers.
Widely known as the Unico System after one of the companies making it, mini ducts are usually employed for air-conditioning, though the system also can be used for heating with an optional electric furnace.