For furnaces, the right size matters

NC)—If your home heating system is more than 15 years old, this winter is a great time to consider upgrading your equipment to more energy efficient models, all the more because of the large number of government, utility and manufacturer incentive programs in effect.

If you do make the decision to replace your heating and/or cooling system, be sure to insist that the installing contractor “sizes” the system properly. To determine the correct heating or cooling capacity of your system, a contractor should perform a “heat loss and heat gain calculation”. This calculation relies on an assessment of the size and age of the home, insulation levels of walls and attic, the type and number of windows, air infiltration rate, indoor design temperature, coldest outdoor temperature found in your area (typically in January) and other factors that influence the rate at which your home loses heat.

The “right-sizing” of replacement equipment is one of the most commonly overlooked methods for ensuring that you get the most from your system. Properly sized equipment performs more effectively and more efficiently, ensuring optimal comfort, less temperature differentiation between floors and maximum energy efficiency. If your contractor refuses to do a heat loss/heat gain calculation, find another contractor.

Over-sizing equipment can result in increased fuel consumption and higher operating costs, potential premature parts failure, higher noise levels, and reduced comfort (including hot or cold spots within the home). On the other hand, under-sizing can result in higher operational costs, particularly with today's sophisticated models. The units will be working at full capacity most of the time, which can lead to premature breakdowns and, more generally, reduced comfort levels.

Furnace technology advanced significantly over the past few years. The introduction of two-stage and modulating technologies have allowed furnaces to provide heating at two or more different capacities. This will allow the furnace to deliver air to the home at a rate which more closely matches the heat loss requirements found throughout the year providing a more even temperature and comfortable environment.

A replacement furnace is not an everyday purchase, so make sure you look at all the options carefully. Remember to get three quotes when considering the purchase of new HVACR equipment, and make sure the contractor you select includes the cost of performing a heat loss/heat gain calculation in the price. You can find a qualified contractor by calling HRAI at 1-877-467-HRAI or online at

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Carol Ireland

Carol Ireland

Sales Representative
CENTURY 21 Millennium Inc., Brokerage*
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