In our automated age, it’s easy to take heating systems for granted—the wood-fueled fireplaces and coal-stoked furnaces once critical for winter comfort in most American homes are long gone. Yet adding or adapting HVAC systems to old houses today often involves a complex web of issues, and modern systems and devices can compete with our desire to preserve the past. So, what's the best way to add heating to your old house?
Central heat, as opposed to fireplace heat, is not a new idea—the Romans used an early version called a hypocaust, and there were isolated steam and hot-water heating systems in Europe by the end of the 18th century. Still, our colonial ancestors relied mostly on open fireplaces with simple andirons to hold split logs. From the late 18th century and increasingly in the early 19th, more fortunate residents of East Coast cities used coal in fireplace grates. Built-in grates of iron or steel were a quality fireplace feature; few have survived intact.
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. Benjamin Franklin’s “Franklin stove” was a cast-iron insert designed to keep more heat inside the room. German settlers made good use of cast-iron stoves, either projecting from a fireplace (the five-plate stove) or freestanding (six-plate).
Old-House Heating Improvements
The 19th century brought improved heating and ventilating systems. Ducted hot-air systems appeared in some upscale homes, and buildings were warmed with heat generated by huge brick furnaces in the cellar, which vented into rooms through floor and baseboard registers, usually with decorative rotating vanes to regulate air flow. As American mines opened, the use of coal increased rapidly, and coal grates often replaced wood in both fireplaces and kitchen stoves. Coal’s advantages were many: small, compact chunks that burned slow but hot—and were delivered directly to the cellar through a coal chute located on the exterior of the house.
The post-Civil War era ushered in hot-air furnaces made of cast iron with a large main grate set in the floor above. Sometimes, in the better systems, sheet-metal ducts fed warm air to other rooms as well. Hot-water- and steam-piped systems with decorated cast iron radiators soon followed. This is where many old-house enthusiasts come in, having bought an old house with one of these antique heating systems.
Mini-Duct Forced Air System
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. It blows treated air at high velocity through flexible 2" or 2½" nylon tubing through unobtrusive vents. It can be invaluable for old-house retrofits because the vents, usually in the ceiling, create little impact on the walls and framing—the tubing can be snaked through and around obstacles, avoiding many of the problems of caused by retrofits of large, solid ductwork. Several outlets may be needed in each room.
The Modern Fireplace
The traditional cozy fireplace can be updated and improved with innovations that include a natural- or propane-gas fire, or new types of inserts. Many attractive metal Victorian-style inserts for coal or wood fireplaces are made with optional matching mantelpieces. Electric heat inserts with faux flames upgrade the old fireplace without gas piping. A Fires of Tradition model features not only faux flames but also smoke in a Victorian-style cast iron unit that requires no venting. For actual wood fires, energy-conserving inserts based on the shallow Rumford design are available. (Fires of Tradition offers traditional grates in a dozen different styles.) Valor Fireplaces offers a variety of gas-fired inserts, which provide heat through power outages.
Hot-Water & Steam Radiators
Common in the late 19th century and standard until the recent past, radiators provide generous heat and are relatively easy to install. After World War II, the hand- or machine-stoked coal furnaces were replaced by ones automatically fed with relatively clean-burning oil. With the arrival of central HVAC systems by the 1960s, hot-water radiator installations faded, except for a growing number of restorationists who delight in decorative antique radiators. The repair and refinishing of old radiators and the sale of antique ones is now a thriving business.
For residential heat, steam was used less than hot water, but both systems are easily repairable. Modern radiators, flatter and updated in appearance, are readily available today; many are made by Runtal, which specializes in wall-mounted flat steel panels. Traditionally, radiators were hidden under wood or metal covers, a practice still widely used. They are made by several companies, such as The Wooden Radiator Cabinet Company and Monarch. An alternative to radiators is baseboard heat, with copper pipes and fins in a sheet-metal enclosure that follows the room’s walls—less desirable because it obscures the historic baseboards. If your house already has them, they can be hidden behind new covers.
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. Seventy years ago, thousands of Levittown houses had radiant heat installed in floor slabs, and Frank Lloyd Wright used it in his Usonian houses. Such early installations were prone to leaks, usually because of eventual pipe corrosion, and originals are difficult and expensive to repair. However, modern radiant heating is much improved.
Today, hydronic panel systems use small, reinforced PEX tubing to carry warm water beneath finished flooring, radiating heat up. The tubing is easy to install on top of a subfloor, and can be finished with wood or tile. PEX comes in coils up to 1,000' long, permitting a single one to be run sequentially throughout several rooms of the house in one circuit, or in separate circuits for zoned heat. It is a flexible system good for old-house rehabs when the flooring is accessible from underneath or can be replaced. (The downside: It supplies heat only, not air-conditioning.)
Electric under-floor radiant systems like those made by Thermofloor and Schluter Ditra-Heat are also easy to install under new finish floors of wood or tile. These are especially useful in small installations like kitchens and baths because they don’t require a separate powered heat source.
Forced-air heating systems also can provide ventilation and cooling, and have been the preferred system in new houses for the past 50 years. However, installing large, insulated ducts in an older house can be difficult and unsightly, or require sacrificing much of the closet space. One solution, assuming that the house has both a basement and attic, is to use floor registers on the first floor with the fan-coil unit in the basement, and ceiling outlets on the second floor, with a separate unit in the attic.