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Furnaces are 26% of the average home's utility bill.

Plan Ahead

Forced air furnaces can last for 25 years, but don't wait until your unit fails.  Planning ahead ensures you can choose a properly sized, efficient replacement, rather than ending up with whatever model is in your contractor's warehouse because it's too cold to wait for something better to be ordered.) 


If your heating equipment is already 10-20 years old, consider replacing it, depending on its size, condition and efficiency --- and definitely if its heat exchanger is cracked and leaking carbon monoxide.  If it isn't meeting your needs, try having it serviced.  If you're still uncomfortable, weatherizing, duct sealing and/or more insulation might solve the problem at less cost.  Consult for more decision-making tips.

TIPS:  An over-sized heating unit can be as uncomfortable as an under-sized one, as well as more expensive to operate.  If your heating unit has to deliver warm air through leaky ducts, it will have to work harder to keep you comfortable.  Before replacing your furnace, it's wise to tighten your home's ducts as well as its "building envelope" (foundation, walls and attic). 

A building performance contractor, such as a HERS rater, can assess whether your home needs weatherizing, more insulation or duct sealing.  


If your furnace has failed and you're in a hurry, tell your HVAC contractor whether you plan to tighten up the envelope, seal the ducts and, if so, how.

Sign up for an LCAN B4UBuy workshop.

Choose Your Technology

With the help of your HVAC contractor, you'll need to choose between various options:

  • Most Louisville homes and small businesses have a gas-fired, forced air furnace.  New gas models should be "two-staged, closed combustion, condensing units." 

  • An air-source heat pump often is a better choice, since they provide AC and most heating needs.  In our area, you'll likely need a back-up gas-fired furnace. 

  • Some older homes and more businesses have boilers.

  • Wall-mounted, ductless "mini-split systems" are the norm for motel rooms, and can make sense for room additions, third-floor rooms used infrequently, etc.

  • Geothermal systems take advantage of the consistent underground temperatures, but usually entail drilling 6-inch diameter, 300-ft deep wells.

  • Radiant floor heating is best for new construction

Find more guidance on choosing from your options here.

Efficiency:  Heating units are rated on the basis of their Annual Fuel Utilization Efficiency (AFUE) score.  The higher the AFUE, the higher its efficiency --- and the lower your operating costs and carbon footprint.  Choose a forced air unit with an AFUE of at least 95%.  Choose an Energy Star-rated unit to you use less power and spend less money with every use.


Design:  Homes and businesses with two-three above-grade stories may benefit from two, smaller "zoned" furnaces: one for the lower floor, and another (often in an attic) for an upper floor.  Restaurants can save and keep diners comfortable by zoning separate systems for the "back and front of the house."

mini-split system cools or heats and cools spaces smaller than a whole house. The left unit mounts on an indoor wall; the right, on an exterior wall.


TIPS:  Visit these web sites for more detailed information: offers guidance on replacing your heating system and tips for operating it more efficiently and cost effectively.


If you don't subscribe to Consumer Reports, you could check out its ratings at the nearest Louisville Free Public Library for additional buying guidance.

You can lower your heating costs in numerous ways, from keeping curtains or blinds open on sunny days, using a ceiling fan on low speed and dressing for the weather to insulating your attic better and planting evergreen trees strategically on the windward side of your home.  Just be sure not to plant trees where they block the sun from reaching your solar panels. helps you to find a model to meet your needs and cut your carbon and costs.

Size Matters

We cannot emphasize enough the importance of right-sizing heating equipment.  If the system is over-sized, you'll be less comfortable and spend more to operate it.  If the system is sized for a leaky building envelope, and you later seal ducts or insulate, it will be over-sized, less comfortable and cost more to operate.

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