There are arguments in favor of side-wall registers. They save floor space and obviate some dust. On the other hand, they are not quite so effective in heating as the other sort, since the pipes for floor registers may be of larger diameter and as a rule require fewer bends. Each register should have a separate pipe from the furnace. Where direct heat is not desired, a register opening in the ceiling of a downstairs room will sometimes carry enough heat to the upper chamber to make it comfortable for sleeping purposes.

Since furnace efficiency is largely dependent upon air control, a strong wind sometimes makes it difficult to heat portions of the house. To meet this emergency there is a combination hot-air and hot-water heater which supplies radiators on the upper floors, or elsewhere if desired. The additional cost is practically all in the installation, as the same fire furnishes both forms of heat.

For an eight-room house or smaller, a first-class steel-plate furnace, securely sealed against the escape of gas and smoke, costs free on board about $150. Each two rooms additional raises the price about $25. Other furnaces may be had as low as $50. Cost of tin work, brick setting, etc., depends upon locality.