ALL ABOUT HEATING

This was high tech in the 1890s:
Radiators used steam or hot water piped
through heavy cast-iron elements.
They got very, very hot.

If you woke up on an icy morning in 1870, the first thing you might do is lug g a bucket of coals up from the cellar and build a fire on the grate.  Makes nudging a thermostat sound pretty easy, doesn’t it?  Heating systems have come a long way since coal fires, but there’ve been a few detours along the way.    

During the late Victorian era, large homes were heated by steam radiators connected to coal- or oil-fired boilers. But while steam heat was clean and comfortable, it was also temperamental.  The systems became encrusted with scale, lost efficiency, and leaked.  

Old style "octopus" gravity furnace, which had to be
below floor level to work. When basements began
to go away, so did this style of furnace.

The cost and complexity of steam systems impelled a change to simpler warm-air gravity furnaces around the turn of the century. Some used ducts to distribute warm air from the basement to individual rooms, while others had a single large floor grille optimally positioned to barbecue your feet. Both types relied on the fact that heat rises to distribute warm air throughout the house—plausible, but not always successful.

Following World War II, the sluggish air distribution of the gravity furnace was finally remedied by the addition of an electric blower that also allowed for smaller duct sizes. Such “forced-air” furnaces, basically unchanged, remain the most popular heating systems in use today.

Forced-air furnace, circa 1970 or so.
Compared to modern versions,
it's a real energy hog. If you've still got
one of these, think about replacing it.

A few other heating systems have come and gone in the meantime, however.  
In the Fifties, radiant heating using hot water pipes embedded in concrete floor slabs made a promising entrance—and a humiliating exit after leaks required countless slabs to be jackhammered up for repair.

By the early Sixties, cheap electricity made electric resistance (coil) heating look like the wave of the future. Clean, compact, and cheap to install, it was just catching on when the lid blew off oil prices. Suddenly electricity (much of it generated by oil-fired plants) didn’t seem like such a cheap heat source after all, especially compared to the lower cost-per-Btu of natural gas. The passage of energy-efficiency regulations, beginning with California's Title 24 standards of 1978, gave watt-gobbling resistance heating the coup de grace by  discouraging its use in residential buildings.

What’s left?  Here are a few of the most popular heating systems in use today:  

Electric baseboard heat: Once
the wave of the future, now
a big no-no.

•  That old warhorse, the forced-air gas furnace, is still the most common residential heating system because of its low initial cost and high reliability. Modern units are now up to about 96% efficient—far better than the dismal 50-70 percent efficiencies of earlier furnaces. On the down side, forced-air furnaces can be noisy, and because they recirculate particle-laden room air, they can aggravate respiratory conditions.  

Radiant heat tubing laid out in preparation for
pouring of gypsum concrete. If you always
have cold feet, this is the system for you.

•  Heat pumps, which work on the same principle as refrigerators, have the added feature of integral air conditioning. Because they use the same type of duct system as gas forced-air units, they’re well-suited for retrofitting. Technically, heat pumps are better than 100% efficient (they yield more energy in heat than they consume in electricity), though these savings are offset by the higher cost of electricity versus gas. They also have a substantially higher first cost, and require a bulky condenser unit that must be located outside the house. Heat pumps work best in a mild climate, as their efficiency drops quickly in very low temperatures.

•  In-floor radiant heating, much improved since the Fifties, has been making a comeback. Radiant systems using hot water tubing embedded in floors are clean, quiet, and comfortable, though their first cost is high. Also, since radiant systems don’t circulate air, a separate means of ventilation is sometimes advisable.