By Regina P. Brown
While we typically would not check “under the hood” of a house, we do verify that the visual components are available and appear to be in good condition. Here is a primer for real estate professionals who want to know what’s going on behind the walls when they need to advise their buyer or selaler clients.
When taking a listing, do you know what to mark in the heat/cooling fields? Learning the HVAC components will help you understand and describe your listing. When working for your buyer clients, product knowledge equips you to recognize defects and negotiate repairs shown on a home inspection.
HVAC stands for “Heating, Ventilation, and Air Conditioning” which refers to the air coming into, going out of, and circulating through a house. System components include a furnace (heater), air ducts, vents, filters, and optionally a cooling system. The HVAC system is designed for health and comfort. This acronym is pronounced “H - vac” or “H-V-A-C”. Let’s take a look at components that are the basic mechanical systems in a residential house.
Heating & Furnaces
Furnaces are mandatory — they must be installed and operable, per government guidelines. Legally, residential house MUST have a permanent heat source. A plug-in room heater will not suffice.
A furnace is the technical name for a heater. Heating fuel includes gas, oil, propane, coal, and electricity.
Heat sources may consist of:
- Electric
- Natural Gas
- Propane
- Coal
- Pellets
- Wood
- Solar
- Air
- Hot water
- Steam
Fuel sourced furnaces (gas and oil) require a pilot light to stay lit, and must exhaust the gases to the exterior of the building. An electric furnace uses heating elements to warm the air. Wood and coal furnaces burn the fuel in a sealed firebox. Older homes may have an oil tank in the basement or buried underground, which will eventually leak or deteriorate and be hazardous environmentally.
Forced Air Unit (FAU)The most common type of central heating, FAU consists of a furnace that generates heat, which is then blown throughout the house via ducts and vents. The furnace may be located in the attic, basement / crawl space, or closet. The closet-type furnace may be located either inside or outside the house. If located outside, it pulls in exterior air and may be less of a carbon monoxide threat for residents. FAG (forced air gas) and FAE (forced air electric) are common abbreviations on home inspections. |
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Wall HeaterPermanently installed wall heaters are usually gas-fueled, but may also run on electric power. Often seen in homes built between 1950 and 1970 because then builders switched to central HVAC systems. Wall heaters are viewed as inferior to central HVAC systems, since the heat is disbursed from only 1 location. The thermostat is either on the wall next to the heater, or within the bottom of the heater itself. |
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Fireplace / Wood Burning StoveAlthough a fireplace or wood stove may radiate a lot of heat, it will not be the primary source of heat for a residential home. Fireplaces that burn wood often disburse ashes and dust throughout the house, which can be detrimental to asthma sufferers. Stoves may also burn fuel-efficient pellets rather than wood. |
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Radiant HeatingRadiant heating is a system of water tubes (hydronic) or electrically heated pipes underneath the floor. Although it heats a room slowly, the room stays warm for quite a while because the heat rises to the ceiling. These systems are rare but may be found in condos that are built with electricity as the only power source. Also seen in home renovations for specific rooms, such as under tile floor in a bathroom. |
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Floor FurnaceIn older houses, the furnace may be located under the house, often in an old-fashioned fuel boiler, and send the heat up through the floor with a vent located in the middle of the house. The large metal vent can get quite hot, which may be dangerous for residents walking on bare feet! |
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Propane TankIn rural areas without gas utility pipes to the property, residents will usually have an outdoor propane tank that feeds fuel into the house. It must be filled by a professional propane company and maintained by the homeowners. The tank will eventually rust due to exposure to the elements. |
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RadiatorAn old-time radiator is a metal heater that contains water or radiator fluid. When turned on, it heats up the liquid and disburses heat. Radiators heat a specific space, usually only 1 room, and can take quite a while to warm a room. They are usually seen in houses that were built over a century ago. |
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Baseboard HeatersBuilt into the baseboard, these small, long heaters are usually powered by electricity. They are often added into rooms in older homes that were built without central heat or as supplemental heat sources for add-on rooms. |
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BoilerBoilers are rare, but may be seen in older houses, especially on the East Coast. |
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Air Conditioning & Cooling
Residential houses are not required to have air conditioning or cooling capabilities, even in the desert with 120° hot summers. Just like with furnaces, optional cooling devices range from inexpensive portable “swamp coolers” to complex whole-house multi-level auto-adjusting air conditioning systems. Air conditioning systems are ranked by SEER (Seasonal Energy Efficiency Rating). EER (Energy Efficiency Rating) and Energy Star both measure energy efficiency. “A/C” is a common abbreviation for Air Conditioner.
Central Forced AirForced air systems pull in air, cool it, and then distribute throughout the house via ducts and vents. Central or whole-house air conditioning systems are common in areas that are either hot, or warm and humid. Residential central air conditioners are usually split systems — the condenser and compressor are outside the building, while the evaporator operates in the house. |
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Evaporative CoolersEvaporative “swamp” coolers – installed in a window or a wall – can be portable. They operate quite efficient as they draw in outdoor air and cool it over water-filled pads. These units “leak” onto the ground as they dispense used water and may not be visually appealing. They only cool one room at a time, so multiple coolers will be needed throughout the house. They are viewed as inferior to central forced air systems. |
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Attic FanAn attic fan works very efficiently by sucking in the hot air at the ceiling or attic level, and expelling it from the house. It then re-circulates the cooler air into the home. |
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ChillerA chiller operates by distributing cold water to air cooling coils via pipes throughout the house. It also includes a hot water boiler for the heating system, with separate pipes for hot and cold water. Although expensive, chillers are highly energy efficient. |
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Fans and VentilationCeiling fans, as part of a light fixture, can be installed in most any house. Other fans may include bathroom exhaust fans, range exhaust fans, and wall louvers for summer time cooling. In addition to cooling, fans help to circulate clean air. |
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Other cooling systems include:
Gas air conditioner |
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Electric air conditioner |
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Heat Pump (water source or electric) |
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Ventilation & Air Distribution System
Besides the heating and cooling components, the ventilation system is comprised of vents, registers, filters, ducts, and thermostats.
Vents & RegistersIn a central air ventilation system, common in most California homes, fans pull in the air through a register, heat the air, and then blow it into the house through small vents. When inspecting the house, often you will observe a large intake vent in the ceiling which leads to the furnace in the attic. Sometimes the intake is a series of small registers in the floor or on the wall. Observe the vents — do they have filters? Are the filters dirty? Are the filters inhibiting air flow? |
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DuctsThe air is distributed through ducts, usually in an attic or crawl space under a house. The air quality of the home is determined by the intake air, and also by the cleanliness of the ducts, and how well they are connected to each other. A duct system that harbors mold or bacteria could have a toxic effect on its residents. Likewise, ductwork that is deteriorated, broken, or inhabited by rodents can pull unwanted elements into the house. |
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ThermostatsThe furnace and cooling system is controlled by a thermostat. Tech savvy thermostats regulate heat automatically or remotely from a smart phone. Newer programmable thermostats can save substantial energy costs. |
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Air Quality
Besides regulating heat, cold air, and air flow, a mechanical system can help control humidity. Accessories can be added to HVAC systems to improve the air quality and enhance circulation. Some indoor air quality options include:
HumidifiersAdd moisture to the air in an arid climate
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De-humidifiersRemove moisture from the air in a damp climate |
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Air Purifier |
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UV Lamps |
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Attic Fans |
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Ventilators |
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Optimal air ventilation can eliminate allergens to reduce allergy attacks, and help asthma sufferers better control incidents. A HEPA air filter can be easily added to a central HVAC system.
System Types
HVAC systems may be installed as packaged systems, zoned systems, split systems, duct-free split systems, and hybrid heat systems. A zoned system means that specific areas of the house have individual controls which heat/cool only certain rooms, saving money and energy.
The split system is most popular in residential houses. It has an indoor furnace and an air conditioner that sits outside the building, with air ducts installed throughout the home. Less popular is the packaged system that accommodates smaller houses. A hybrid system is a gas furnace heater with the addition of an electric heating or A/C system. Compare that to a duct-free system, which is a heat pump or A/C with a fan coil.
In hot humid areas, single stage cooling is popular, as is single stage heating in cold winter climates. However, single stage is not the most efficient, because it means that the HVAC system is running full blast around the clock. They can save energy costs by upgrading to a multi-stage system and by installing Energy Star Certified appliances.
GREEN Conversion
Converting a home to GREEN energy can save both money and environmental pollutants. Because they can reduce energy bills, GREEN homes offer advantages to buyers, and therefore may be valued higher by sellers and appraisers.
GeothermalGeothermal energy harnesses the earth’s natural heat below the surface. Heat pumps route tubing under the ground to warm the liquid in the pipes and capture the natural heat, which is usually a constant temperature year-round. During warm summer months, the system cools the home by reversing the heat exchange. |
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SolarTwo types of solar systems, passive and active, are being adapted for home energy power. Both collect energy from the sun, which is a renewal energy source that never runs out. “Passive solar” means installing pipes in walls and floors to gather and store energy. Windows also can be used to capture the sun’s rays. “Active solar” means installing panels or solar cells on the roof. The power collected with a photovoltaic system is then stored and distributed through the home’s mechanical system as heat. A new technology uses water or air to absorb solar energy, which is more efficient and less expensive. Watch for scientific developments. |
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BiodieselBiodiesel is a fuel blend of organic biofuel mixed combined with heating oil. Biofuels are sustainable because they are produced from corn, soy beans, wheat, and sugar cane crops. The main benefit is that the environment receives less pollutants. |
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Hydronic HeatingHydronic (water) heaters transfer liquid heat through convection, conduction, or radiation. The liquid heats radiators, floors, or baseboards similar to the old-fashioned radiators, but is heated with solar or geothermal energy. |
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AbsorptionAn absorption heating and cooling system uses solar, geothermal, or gas power and operates similar to a regular heat pump. However, it uses ammonia instead of a refrigerant as the heating/cooling liquid in the pipes. |
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Ice-Powered Air ConditionerIce Energy company is leading a GREEN revolution! The machine makes ice at night, which cools the air conditioning system during the day. |
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Green CoalCoal, often viewed as a toxic fuel, can actually be environmentally friendly. With a gasification process, the carbon in the coal is used to strip oxygen from water and create clean-burning hydrogen gas, which is used for fuel. The emissions and pollutants are disposed using eco-conscious techniques. |
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Wind PowerWind turbines are being developed smaller and more efficiently, and can actually generate heat for a water heater. Using magnets and magnetic resistance with copper plates, this sustainable energy source can be a permanent heat source for a house. |
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BiomassEnergy that is produced from living organisms, trees for example, is known as biomass. This natural and renewable energy source converts stored energy from the sun into heat energy. Woodchip systems, for example, emit less pollutants than wood stoves and produce fewer carbon dioxide than gas or oil. |
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Conclusion
Now you know the HVAC lingo for houses. Your experience is showing! The next time you take a listing, show a house to a buyer, or read a home inspection report, you’ll be prepared with the right terms at the tip of your tongue.
Article is also published in The San Diego Realtor® magazine, pages 28, 29, & 31.
Read more in our "Learn the Lingo" series:
1) Backyard & Outdoor Structures: Learn the Lingo
2) View From the Windows: Learn the Lingo
3) Architectural Styles: Learn the Lingo - Part 1
4) Architectural Styles: Learn the Lingo - Part 2
5) Learn the Lingo: Luxury Bathrooms
6) Learn the Lingo: Fences & Gates
7) Learn the Lingo: Vintage Features of Historic Homes
8) The Kitchen: The Heart of the Home Can Be Gourmet
9) The Gourmet Kitchen: Everything and the Kitchen Sink
10) Open the Door of Possibilities (Exterior Doors)
11) The Difference a Good Door Makes (Interior Doors)
12) Tiles
13) Sustainable and Eco-Conscious Home Features (Part 1)
14) Sustainable and Eco-Conscious Home Features (Part 2)
15) Sustainable and Eco-Conscious Home Features (Part 3)
16) Roof Architecture – Don’t Let it Go ‘Over Your Head’
17) Let There Be Light Fixtures ... And There Are Many!
18) A Discussion of Ceilings Will Have You Looking Up
19) Fireplaces: Literally the Hearth of the Home
20) Learn the Lingo of Walls
21) Apply Your Knowledge to Major Appliances
22) Don't Be Floored By this Topic: It's Right Under Your Feet
23) HVAC / Mechanical Lingo
24) Rural Properties - A Sustainable Life "Off the Grid"
25) Land Usage, and Showing & Selling Rural Properties
26) The Dramatic Effect of Stairs and Staircases - A Flight of Fancy?
27) Electrical Components - Get Wired for Understanding
28) Learn the Lingo: Plumbing Fixtures (Part 1 of 2)
29) Learn the Lingo: Plumbing Fixtures (Part 2 of 2)
30) Swimming Pool and Spa Lingo
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