Types of Heating Systems: Enhancing Comfort in Your Home

Central Heat: Embrace the Warmth

In the chilly winters of North America, a central furnace becomes the heart of countless households, providing the much-needed heat. Picture this: a furnace diligently blowing warm air through a network of ducts, ensuring every room in your home is enveloped in cozy warmth. This remarkable system, known as a ducted warm-air or forced warm-air distribution system, can be powered by electricity, natural gas, or fuel oil.

Within the confines of a gas- or oil-fired furnace, a delicate dance of fuel and air takes place. The resulting flames generate heat that is then transferred to the surrounding air through a metal heat exchanger. A dedicated furnace fan, aptly called the "air handler," propels the heated air through the ductwork, allowing it to reach every nook and cranny of your abode. The combustion by-products find their way out of the building via a flue pipe, ensuring a safe environment. In the past, "atmospheric" furnaces released these by-products directly into the atmosphere, wasting a significant portion of the fuel's energy in the process. However, modern furnaces combat this inefficiency by incorporating an "inducer" fan, which draws out the exhaust gases, enabling draft in the chimney. Notably, "condensing" furnaces take efficiency to new heights by recovering the escaping heat and converting water vapor into water. This exceptional feature characterizes high-efficiency furnaces, and their venting is accomplished through a sidewall pipe, typically made of plastic.

While the current furnace standards date back to 1987, the U.S. Department of Energy is diligently working on updating these standards, with the finalized version expected to emerge in the spring of 2016. These new standards aim to further enhance the efficiency of heating systems, promising a brighter and more sustainable future.

Heating system controls, including the all-important thermostat, play a vital role in regulating the operation of various components. Your comfort hinges on the thermostat's ability to activate or deactivate the system as needed. Though a typical forced air system relies on a single thermostat, internal controls, such as "high limit" switches, work silently in the background, ensuring safety remains paramount.

Furnaces and Boilers: Harnessing Efficiency

When it comes to efficiency, modern gas furnaces and boilers reign supreme, boasting efficiencies over 90%. These systems are designed to maximize the useful heat produced per unit of input energy, delivering warmth in the most efficient manner possible. The measure of combustion efficiency provides a glimpse into the system's performance while in operation, much like how your car's efficiency is gauged by its mileage on the highway.

In the United States, furnace efficiency is regulated by the Annual Fuel Utilization Efficiency (AFUE), which provides an estimate of the system's seasonal efficiency under various operating conditions. AFUE factors in start-up, cool-down, and other operational losses, including the electricity consumed by the air handler, inducer fan, and controls. Similar to assessing your car's mileage between fill-ups, a higher AFUE signifies a more efficient furnace or boiler.

Boilers, unlike furnaces, employ a different mechanism to distribute heat. These specialized water heaters circulate hot water through radiators or other devices, releasing heat as the water passes through them. Commonly fueled by natural gas or heating oil, boiler systems offer a reliable source of warmth in countless homes. Steam boilers, though less prevalent nowadays, use boiling water to generate steam that travels through the house, transforming back into water within the radiators. Both oil and natural gas can fuel these boilers effectively. 

Boilers

Boilers, the remarkable marvels of home heating, are specialized water heaters. Unlike furnaces that disperse warmth through the air, boilers gracefully distribute heat through hot water, which generously releases its warmth as it flows through radiators or other ingenious devices positioned strategically in every room of your beloved abode. The cooled water then gracefully returns to the boiler to be embraced by the warm, soothing flames once more. These magnificent systems are often referred to as hydronic systems, and in residential settings, they usually rely on the natural power of gas or heating oil to fuel their enchanting dance.

Within the realm of steam boilers, although less prevalent in today's modern homes, water is transformed into a spirited vapor that carries its heartwarming essence throughout the house, gracefully condensing back into its liquid form within the loving embrace of radiators. Oil and natural gas serve as the faithful companions in this enchanted journey.

Instead of the customary fan and duct system found in other heating marvels, a boiler elegantly employs a pump to delicately circulate hot water through a network of pipes, allowing the essence of warmth to radiate from majestic radiators. Some ingenious hot water systems even weave their magic through plastic tubing embedded in the very floors of your sanctuary, presenting radiant floor heating, a testament to the extraordinary artistry of modern heating (see the awe-inspiring "State of the Art Heating"). As for the guardians of this wondrous dance, we cannot overlook the pivotal role played by thermostats, aquastats, and valves that govern the gentle flow of warmth and maintain the water's delightful temperature. While the installation cost may not be insignificant, the grace of a hydronic system reveals its true magnificence in the simplicity of incorporating "zone" thermostats and controls for each individual room, a feat far more effortless than in the realm of forced air. Some controls come as standard features in new boilers, while others can be added to bestow the gift of energy conservation (see the enlightening "Modifications by Heating System Technicians" section on the sacred page of heating maintenance).

Similar to furnaces, the world of condensing gas-fired boilers welcomes you with open arms, for they are a familiar sight, boasting tremendous efficiency when compared to their non-condensing counterparts (unless, of course, the presence of extraordinarily sophisticated controls is at play). However, it is important to note that oil-fired condensing boilers are scarce in the lands of the United States, with reasons deeply intertwined with the modest latent heat potential and the potential for greater fouling when conventional fuel oil graces the stage.

Heat Pumps

Behold, the mystical heat pumps, dear companions in the symphony of temperature control. These enchanting devices are but two-way air conditioners, their nature akin to the gods of cooling (please find detailed descriptions in the illustrious cooling systems section). During the radiant summer days, an air conditioner dances with fervor, diligently transporting heat from the blissful indoors, where coolness prevails, to the scorching outdoors, where warmth triumphs. Yet, in the heart of winter, these heat pumps astound with their mesmerizing abilities, skillfully extracting warmth from the frigid embrace of the great outdoors, with the guiding touch of an electrical system, and generously releasing that captivating heat within the very walls of your cherished dwelling. It is through the benevolent power of forced warm-air delivery systems that these remarkable conduits circulate the essence of warmth throughout the halls of your abode.

Ah, the mystical realm of heat pumps! Within this captivating realm, there exist two commonly encountered types. First, we have the air-source heat pumps, harnessing the very breath of the outside air as their source of warmth during the chilly winter months and a refreshing refuge to release heat during the scorching summer days. Second, we encounter the extraordinary ground-source heat pumps, known by various names such as geothermal, GeoExchange, or GX. These wondrous beings draw their power from the depths beneath our feet, where the temperature remains steadfast throughout the year. While air-source heat pumps hold the throne of popularity due to their affordability and ease of installation, ground-source heat pumps reign supreme in terms of efficiency, attracting those enlightened individuals who seek long-term residence or yearn to tread lightly upon our precious Earth. To determine whether a heat pump is the harmonious choice for your climate, delve deeper into the realm of "Fuel Options."

As the air-source heat pump gracefully takes its place in your abode, its installation mirrors that of a regal central air conditioner. However, when it comes to the awe-inspiring ground-source heat pumps, a sacred ritual must take place. A "loop" must be delicately laid to rest within the earth, oftentimes in shallow trenches or through vertical boreholes, seeking harmony with the soil, the terrain, and the knowledge of the installer. Alternatively, some remarkable systems draw water from the depths, allowing it to flow through the heat exchanger in lieu of traditional refrigerants. The water, having shared its warmth, is returned to the aquifer, completing the cycle of nature's benevolence.

In the magical realm of heat pumps, electricity assumes a noble role as a conduit, guiding the flow of warmth rather than generating it. As a result, the heat pump exhibits a remarkable quality—it delivers more energy than it consumes. This phenomenon is captured by the coefficient of performance (COP), which measures the ratio of delivered heating energy to consumed energy. The values of this enchanting ratio range from 1.5 to 3.5, bestowing a sense of awe and wonder. However, let us remember that the COP represents a "steady-state" measure, distinct from the seasonal measure known as the heating season performance factor (HSPF), which governs the rating of air-source heat pump efficiency. Converting between these measures is a task not easily accomplished, yet it is known that ground-source units often surpass their air-source counterparts in terms of efficiency, revealing the true magic that lies beneath the surface.

Direct Heat

Gas-Fired Space Heaters

In certain realms, the allure of gas-fired direct heating equipment is strong. These remarkable devices, be they wall-mounted, free-standing, or floor furnaces, possess a unique quality—they eschew the presence of ductwork, offering a humble yet efficient means of warming a single room. If the desire to embrace warmth in multiple chambers arises, one must either keep the doors between rooms ajar or seek solace in alternative heating methods. The esteemed models of these enchanting furnaces employ "sealed combustion air" systems, where pipes gracefully traverse the walls, providing the precious air required for combustion while gracefully carrying away the remnants of this fiery dance. Such units are capable of delivering satisfactory performance, particularly in cabins and abodes where the divergence in temperature between bedrooms and main rooms is deemed acceptable. Whether fueled by the natural power of gas or the elegance of propane, some even possess the ability to burn kerosene, adding another layer of mystique to their already mesmerizing presence.

Unvented Gas-Fired Heaters: A Bewildering Choice

Oh, dear reader, let us navigate the treacherous path that leads us to the realm of unvented gas-fired heaters. These devices, sold for decades without an exhaust vent, we must vehemently discourage their use for the sake of health and safety. Known as "vent-free" gas heating appliances, as proclaimed by their manufacturers, they come in various forms such as wall-mounted and free-standing heaters, even alluring open-flame gas fireplaces adorned with ceramic logs that share no connection with a chimney. These manufacturers claim that due to their remarkably high combustion efficiency, these devices are safe for occupants of buildings. Alas, this claim holds true only if you keep a nearby window open to invite an adequate supply of fresh air—a paradox that undermines the very purpose of supplemental heat. The perils associated with such devices include exposure to combustion by-products, as discussed in the realm of Ventilation, and the depletion of precious oxygen (requiring these heaters to be equipped with oxygen depletion sensors). Such hazards have prompted at least five states, including California, Minnesota, Massachusetts, Montana, and Alaska, to prohibit their use in homes, with numerous cities in the United States and Canada following suit, banning them from existence.

Electric Space Heaters

Portable electric heaters, an affordable purchase that conceals a costly secret. These resistive heaters, bearing the names of "oil-filled" and "quartz-infrared," possess the ability to convert electric current from the very walls they plug into into a comforting warmth, akin to the transformational powers of a toaster or clothes iron. However, as we delve deeper into the realm of "Selecting a New System," we unveil the bitter truth—that it requires an immense amount of electricity to produce the same amount of useful heat that natural gas or oil graciously offer onsite. A mere 1,500-watt plug-in heater will consume nearly the entirety of a 15-amp branch circuit, leaving little room for additional loads before triggering a circuit breaker or blowing a fuse. The cost of operating such a unit for a single hour can be calculated with ease—simply multiply 1.5 by the cost of your electricity in cents per kilowatt-hour. At the national average rates of 12¢ kWh for electricity, that heater would drain your pockets by 18¢ per hour of operation, quickly surpassing its initial purchase price. However, in situations where intermittent use is the only option, this may be the "least-bad" solution, sparing one from making substantial investments to enhance the ductwork in a specific area, for instance. Yet, it must be remembered that electric resistance heat stands as the most exorbitant form of warmth and is, therefore, seldom recommended.

Behold, the captivating realm of "electric baseboard heat," another embodiment of resistive heating, similar to a plug-in space heater, but firmly anchored into the essence of your dwelling. It boasts two primary virtues—an affordable installation cost and the convenience of installing individual room thermostats, allowing you to lower the temperature in unoccupied spaces. However, the operating costs, much like all resistive systems, remain alarmingly high unless the house is blessed with the gift of "super-insulation."

Fireplaces: A Warm Glow, But Not the Best Heat Source

Ah, the allure of gas and wood fireplaces, captivating pieces of a room's decor that offer a comforting glow (and a discreet way to dispose of confidential documents). Yet, let it be known that these fireplaces, in their conventional forms, seldom serve as efficient heat sources. They draw air from the room for combustion and dilution, causing the fireplace to lose more heat than it actually provides. The unit greedily pulls warm air through its structure, leaving a void that must be filled by cold outside air. However, if the fireplace is equipped with a tight-sealing glass door, an external air source, and a reliable chimney damper, it can indeed offer some practical heat to warm your abode.

State-of-the-Art Heating: Radiant Floor Heat

Radiant floor heat, a marvel in the realm of modern heating, involves circulating warm water through tubes positioned beneath the floor. This gentle warmth seeps into the floor itself, generously embracing the occupants of the room with its soothing embrace. Advocates of this system extol its controllability and efficiency, but be warned, dear reader, for its installation comes at a steep cost. A skilled and experienced system designer and installer are essential to ensure its optimal functionality. Additionally, one must consider that certain carpet choices and other floor finishes may be restricted, as you wouldn't want to smother the radiant source that provides your warmth.

Ductless, Mini-Split, Multi-Split: Embracing Innovation

Residential ductwork, a rarity outside the realms of North America, gives way to the reign of "ductless" heat pumps. These innovative devices distribute energy through refrigerant lines, eschewing the traditional methods of water or air. Field trials conducted in the Pacific Northwest have shown promising results, indicating commendable performance even in cold weather conditions. For those seeking an alternative to electric resistance heating, these heat pumps can prove highly cost-effective. However, it is important to note that the market for whole-house multi-split systems is still relatively new, resulting in premium prices.

Combined Heat and Power (CHP) or Cogeneration: A Glimpse into the Future

In select countries, the concept of combined heat and power, or cogeneration, is being earnestly explored for residential use. The fundamental idea revolves around employing a small generator to meet a portion of the house's electricity demand while capturing and utilizing the waste heat—often more than 70% of the fuel's heating value—to warm the home and provide hot water. Although these systems are not yet widely available, they show promise, particularly for houses burdened with high heating bills. Solid stone or brick homes, where insulation measures prove challenging, may find these systems economically advantageous.

In the ever-evolving landscape of heating options, it is essential to weigh the pros and cons, seeking a solution that aligns with your needs, preferences, and budget. Choose wisely, dear reader, for the warmth and comfort of your abode are at stake.