How does my home heating work?

How does my home heating work?

No matter where you live in North America, there's a good chance that you're going to need some kind of home heating to keep your home comfortable. Now, while some folks in southern-most Texas may beg to differ, it's no surprise that practically every home from Houston to Dallas has a furnace. Of course, not every region in the U.S. favors the same type of heating system. For example, natural gas or propane heat is favored for most of the Midwest while many Northern cities still retain boilers and radiators.

Because we know our customers save more money by understanding how they use energy, we've put together this basic guide to the different types of home heating systems so that homeowners can learn about the kind of heating system they have and how it works.

The Two Basic Types of Heat Systems

Basically, there are two kinds of heating systems, forced air and radiant.

Forced air systems use a blower or fan to pull air into the system where it is heated and circulated throughout the home. They can be noisy with metallic squeaks from loose connections and require routine air filter changes to keep them running well. But because they heat the air, they tend to warm up homes quickly. A forced air system is composed of air return ductwork, a blower, a heating or cooling unit with heat exchangers housed inside the air handler cabinet, a plenum where the air exits the air handler, and supply ductwork. The supply ductwork carries the air to all the rooms of the home while the return ductwork carries all the air from the rooms back to the blower and air handler.

Radiant systems rely on the use of heat to move air through convection. That is, heated air rises and is replaced by cooler air, which is heated and rises and so on. Because these systems work passively, they tend to heat rooms slowly. Plus, they don't filter dust or allergens from the air, and in some cases, are not as energy efficient. However, most are inexpensive to buy, install, and maintain.

Forced Air Systems

Electric resistance heating is 100% energy efficient because all the electricity is converted to heat. And since the heating elements in an electric furnace are in direct contact with the air, the air heats up very quickly. This makes them very efficient but expensive to operate during extended cold weather.

Other Types of Forced Air Systems

  • In natural gas/propane systems, you want the heat to from a series of flames to heat the air but you also want to send the combustion exhaust out of the house. Gas burns on several long ribbon burners (12" to 18" long). The heat exchanger resembles a tall, hollow hair comb that surrounds each ribbon burner on three sides. The hot gases move up into the heat exchanger and eventually exhaust out into the vent pipe. On highly efficient condensing gas furnaces, so much heat is wrung out of the exhaust that it won't rise well enough to leave. This is why the system uses a fan to blow the exhaust outside.
  • Heat pumps include both air condensers that are installed outside and geothermal condensers that are buried underground or in nearby water. Both use R-410A refrigerant that is also used in air conditioning, but the process runs in reverse so that instead of warm air being expelled outside as waste heat, it's blown inside to supply heat. Heat pumps use compressor/condensing systems similar to regular air conditioning systems except that they are reversible. Geothermal systems do basically the same thing, but instead of relying on the ambient air temperature to make heat, they use the temperature of subsurface ground which stays around 50°F, making it very reliable and energy efficient.
  • Ductless heat pump/AC systems are forced air systems that don't use ductwork. Sometimes called "split systems", the interior air handling and heat exchanging unit is directly connected to through the exterior wall to the outside unit. Because of their small size and the fact that they don't use ductwork, split systems like these are best suited for heating and cooling small areas.

Cost of Forced Air Systems

The installation costs of these systems vary significantly depending on the circumstances. Electric resistance, natural gas and propane systems are often the most affordable option in new construction and in homes with existing duct networks. But if you need to install a duct system in an existing home, the cost of the ductwork may be several times the cost of the heater itself.

The installation and equipment costs of air heat pumps are often twice as high or higher than the costs of installing electric, gas or propane furnaces. And geothermal heat pumps are typically the most expensive to install, with installation costs dependent on the complexity of the installation of underground piping. Some geothermal systems can cost more than $20,000 including equipment and installation.

Ductless systems may be the cheapest option if you're only heating one room, but because you need a separate system for each heated space, the installation and equipment cost increases with the number of systems.

As for operating costs, geothermal heat pumps are the most affordable, followed by air heat pumps and ductless systems. Among electric resistance, natural gas and propane systems, natural gas is typically the most affordable, but the operating costs are tied to the fluctuating costs of their energy sources: electricity, natural gas and propane.

Maintenance of Forced Air Systems

Airflow is the lifeblood of any forced air system, and the chokepoint for that airflow is the filter. Every forced air system has a filter that must be replaced or cleaned on a certain schedule, and neglecting to perform this maintenance on time can result in higher operating costs and increased system wear.

Any system with an outdoor condenser installed at ground level (this excludes geothermal heat pumps and ductless systems) requires some additional DIY maintenance. The condenser should be kept free of weeds and debris and should occasionally be gently hosed off to clear away dirt.

All other maintenance should be performed by a licensed HVAC professional once per year, ideally before the start of heating season. This maintenance should be performed every year, no matter how well the system is performing. Annual maintenance extends the life of the system, optimizes energy efficiency and ensures the system's safety.

Radiant Systems

In the case of all heat radiating systems, they work silently and don't buffet a room's occupants with blasts of hot air. However, they tend to work more slowly to warm up a room when compared to forced air systems. This is largely due to the fact that they rely on convection to heat the air and make it circulate through the room. That said, some types of radiant systems work faster than others.

Radiant heat can be more efficient than forced air systems with duct loss problems, and some people with allergies prefer it because the lack of air circulation doesn't stir up allergens. However, because these systems circulate water as either steam or liquid, radiator systems can be prone to problems such as blockages and leaks.

Types of Radiant Systems

  • Passive solar is the greenest and least expensive to operate because the sun's heat is stored in the thermal mass of the home. The sun's heat radiates and warms the space. However, your home needs to be very well air sealed and insulated plus have adequate southern exposure to allow enough sunshine to enter the windows and warm the home. Unfortunately, the further north you go, the more expensive it can be to build a passive solar home and you may well need to have backup heating during cold snaps.
  • Boiler-based systems include radiant floor heat that uses hot water, old-fashioned radiators that use steam or hot water, and also some hydronic (liquid-based) baseboard systems (see below). In these systems, a central boiler heats the water (or other liquid) to either steam or hot water and pumps it through pipes throughout the home to radiators or coils of tubing embedded in walls or flooring.
  • Radiant floor heat makes use of the floor's thermal mass. When you take hot water tubing and arrange it in loops on the floor and then a surround it with poured concrete (wet installation) or a sandwich of tile and plywood (dry installation), the floor will stay warm longer and radiate the heat longer, which keeps the room warm longer and more evenly. The bigger the floor space, the more of it can be heated and the more heat it will store.

Baseboard Heat: Electric (or "Convective") and Hydronic Heaters

These heating systems work best when they are mounted at least 3/4" above the floor or carpet. This allows cooler air on the floor to flow through the heater fins and be heated. One drawback is that fur from shedding pets can get pulled into these kinds of heaters and block airflow.

  • Electric baseboard heaters (that use electric resistance heating elements) are mostly zonal heaters so each is controlled by a built-in thermostat. Available in lengths from 3 to 6 feet, each foot draws about 250 watts. Electric baseboard heaters tend to be the least expensive, easiest to install heating system. They only need to be wired up (with either 120 or 240 wiring) and fastened to the wall.
  • Hydronic (liquid-based) baseboard systems use water or oil instead of electric resistance and tend to be a bit more expensive. In electric resistance systems, once the current shuts off, the heating element goes cold in just a few minutes. But in hydronic systems, once the liquid is hot, it stays hot longer —making them a little more efficient to operate than electric resistance baseboards. Hydronic systems can be installed as individual units or as a single whole-house system that uses a single heater, much like a radiant or radiator system.

Cost of Radiant Systems

The installation costs of radiant systems tend to be even more difficult to estimate than those of forced air systems. With passive solar heating, for example, the heating elements are integral to the construction of the home and could add anywhere from a few thousand to several tens of thousands of dollars to the total cost of designing and building new construction.

With boiler-based systems, the cost of boiler installation ranges from a few thousand dollars (comparable to electric, gas or propane furnaces) for smaller boilers into five-figure sums for larger ones. If radiators, hydronic baseboards or floor heat piping must be installed, the cost is tied directly to the number of units or square feet of flooring. So the cost of both the boiler and the heat distribution equipment increases with the size of the home.

Similarly, the cost of electric radiant floor heat installation usually boils down to a price per square foot, so the total cost depends on the size of the home.

In the typical home, the operating costs of these radiant systems tend to be lower than those of electric, gas and propane furnaces but higher than those of heat pumps. As with installation, however, this can vary along with the size of the home. Electric radiant floor heating is expensive to operate, for example. In a very small home, this may be cheaper overall than installing a furnace and ductwork or a series of mini-split systems. But in a huge home, heating entirely with electric radiant flooring could be a costly mistake.

Maintenance of Radiant Systems

Compared to forced air systems, radiant systems are much easier and usually cheaper to maintain. An annual boiler inspection and tune-up is typically the only routine maintenance cost associated with boiler-based systems.

Passive solar homes are maintenance-free on the inside, but can require ordinary outdoor maintenance like clearing gutters, trimming trees and washing windows to ensure sufficient exposure to the sun's warming rays. Electric radiant flooring is also essentially maintenance-free; unless the system isn't performing as expected, you may only want to schedule an electrical inspection every several years, as you would with the other electrical infrastructure of your home.

Electric baseboard heaters do require routine cleaning of vents, especially if your home is dusty or you have pets.

Which Type of Heating System Is Best?

It really depends on how your home is built, what you can afford, and what you prefer. For example, if you are building an addition or are modernizing your home's HVAC, you may find that it might not be feasible to run new ductwork to different parts of your home. In which case, you might need to consider some type of baseboard system coupled with a ductless mini system for summertime cooling. And while it has been argued that forced air systems do stir up allergens, when they are equipped with HEPA air filtration, they do a much more efficient job of purging allergens from the air throughout the entire home. If it's a matter of energy efficiency but passive solar is not a practical choice, the most efficient is a geothermal heat pump followed by its cousin, the air heat pump. While these are very effective heating systems, during events like cold snaps they require heating backups — usually in the form of built-in auxiliary electric resistance heating elements.

If you're thinking about updating your home's heating system or even just need some maintenance, it's best to contact a skilled professional like One Hour Air Conditioning and Heating for expert service.

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