To calculate energy savings with increased insulation Fuel Comparison To compare heating costs using various fuels. To size a room air conditioner. Radiant in each room can be electric, wood stove, gas heater , kerosene, coal, a fireplace, etc.
Central systems can be hydronic, steam or forced warm air.
Hydronic and steam are detailed under hydronic elsewhere in this site. This means it must obtain air from the home by way of a return air duct or ducts. Properly installed, a warm air system becomes a loop by which air is drawn from the living space through return ducts to the furnace, heated, and sent back to the same space through supply ducts. The advantages to this type of heating system are numerous. Supply ducts located around the outside walls of the rooms will temper the cold air as it infiltrates the home and reduce any discomfort from the air flow to a minimum.