Greater Austin Area Heating & Furnace Repair & Replacement

Travis County: Austin, Round Rock, Cedar Park, Pflugerville, Leander, TX

More than 65% of U.S. homes are heated with central forced-air furnaces. Most furnaces heat air by burning gas, oil, or propane. Some use electricity to heat an element. 

How Does a Furnace Work

• The furnace burner is located in the air handler box along with a fan. 
• The fan blows the heated air into supply ducts, for distribution to registers located throughout the house. 
• Air from individual rooms or common areas is drawn into return registers and brought back through return ducts to the furnace air handler where it is reheated and redistributed.

Furnace Efficiency

The efficiency of a furnace or boiler is measured by annual fuel utilization efficiency (AFUE). 

What Is an AFUE Rating and What Does It Cover?

• An AFUE of 90% means that 90% of the energy in the fuel becomes heat for the home and the other 10% escapes out the vent pipe and through the furnace jacket. 
• AFUE doesn’t include the power consumption of the fan and controls. 
• Nor does it include heat losses of the duct system, which can be up to 30% or more when ducts are leaky, poorly insulated, and located in an uninsulated attic or crawlspace. 

If not properly maintained, the actual efficiency of the furnace can be significantly lower than the rated efficiency.

Low-Efficiency Furnaces (Less than 78%)

While nearly all furnaces sold today have an AFUE of at least 80%, many older, less efficient furnaces in the 56% to 72% range are still in operation, including even old coal burners that have been switched over to oil or gas. 

How to Check If a Furnace Is Old

• If a furnace has a pilot light, it was probably installed prior to 1992 and likely has an efficiency of less than 72%. 
• Old gas furnaces may lack a vent damper (which saves energy by limiting the flow of heated air up the chimney when the heating system is off).

How Does a Natural Draft Furnace Work

Older style furnaces can be called draft-hood furnaces because they draw combustion and dilution air from the room in which they are located; the dilution air enters through a draft hood (also called a draft diverter). 

How Does an Oil Furnace Work

Oil furnaces use a barometric damper instead of a draft diverter for dilution air in the chimney or vent system to decouple the burner from the chimney, thus avoiding poor combustion.

How Do Older Style Furnaces Work

Older style furnaces rely on natural draft to carry exhaust gases out of the home. The combustion gases exit the home through the chimney using only their buoyancy, combined with the stack effect of the chimney’s height. Naturally drafting chimneys can have problems exhausting the combustion gases because of chimney blockage, wind, or depressurization of the home, which can overcome the buoyancy of the gases.

What Is Depressurization in a House? 

Depressurization is a situation that can occur if more air is being pulled out of the home than is being drawn into the home through air leaks or intentional ventilation. Certain changes in the home can lead to depressurization.

For example, if a new kitchen range is installed with a high-powered exhaust fan or if a significant amount of air sealing is done. These changes could possibly increase the risk of backdrafting, where exhaust products spill back into the house rather than going up the flue. 

A certified energy contractor will conduct combustion safety testing as part of any combustion appliance repair or replacement or air sealing project. The testing will ensure that the furnace and combustion appliances have adequate combustion air and are venting properly