Furnaces come in 3 types of efficiencies. Low, mid and high. The lowest efficient furnaces are typically 40 years old or more. You’d be surprised how many of these are still in use in homes. I live in Cincinnati, former home of Williamson furnace company. You can identify a Williamson furnace, becuase they are typically green in color, and are rougly twice the size of a newer furnace. Williamson’s and other furnaces of this ilk, are considered very inefficient by today’s standards. They have standing pilot lights, no draft induction motors or dampers inside the flue pipe, and are often times oversized for the square footage of the home. The efficiency of this type of furnace is probably less than 50%, meaning for every dollar you pay in natural gas, you get 50 cents or less in heat supplied to your home. The rest of the heat escapes up the chimney flue, lost forever.
Mid efficiency furnaces started cropping up in the 1970’s. Generally a mid efficiency furnace is 80% or more efficicient. So for every dollar spent, 8o cents or more is actually being used to heat the home, while the rest escapes up the chimney. Mid efficiency furnaces are still used and installed in homes today. Often times they are used in milder climates and places where the winter months are shorter.
A furnace that is 90% efficient or greater, is designated as “High Efficient” One way to determine if a house you are looking at has a high efficient furnace is to look at the flue pipe. PVC piping is used to vent the highly efficient furnaces. The reason being is that because so much of the heat is extracted from the natural gas, the exhaust gases cannot rise fast enough on their own through a brick chimney. Instead, an induction fan motor is used to pull the cooler exhaust gases through the PVC pipe and is usually vented through the wall to the exterior.
If you are looking to buy an older home, say one that was built prior to 1960, take a look at the furnace and try to determine if it is a low, mid or high efficient furnace. If it is of the lower variety, replacement in the near future is likely going to be needed. For one, a furnace that is still in use after 20 or more years is living on borrowed time. Also, the amount of money you could be saving every winter on your gas bill is significant, making the payback or return on your investment sure to happen relatively fast. When I bought my first (and only) home 6 years ago, I had one of those older Williamson models. It heated the house very well. Maybe even too well. While there was no shortage of heat, there was certainly a low level of comfort, as the furnace cycled on and off, heating rooms too much, then shutting off, only to feel cold again before it came back on. One month after purchasing the home but not having moved in yet, I received my first gas bill. With the termostat set on 50 degrees, just to keep the pipes from freezing, my bill was over $350.. Holy cow was I shocked. One month later, still in the dead of winter, and having moved in, I had a high efficient Bryant furnace installed. Even with the thermostat set to a comfortable 70 degrees, my gas bill went down to $240 bucks. Almost a 33% decrease. Not only did I save money, but the indoor temperature was more steady and ultimately my comfort level increased.
Another advantage to replacing an older furnace, is that at this time (July 2010) there is a Federal Tax rebate on high efficiency products, which can be significant and speed up the pay back time on your new furnace. Something worth looking into.
