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Spotting A High Efficiency Gas Furnace, 3 Quick Tips

After a recent outing with buyers of mine the subject of gas furnace efficiency came up. My buyers were interested in some tips to spotting a high efficiency furnace. I thought I might share my discussion I had with them and help out anyone else with the same question. Watch the video or read below. Either way the fun doesn't end with all there is to know about furnaces! Keep in mind these tips only work with a properly installed furnace. If a furnace was installed with duct tape and bubble gum there is a good chance these tips will be of little help.

Tip #1 The Energy Guide Sticker...... Yes, It Can Be That Simple:

The Energy Guide Sticker is that big yellow label on the side of all new furnaces. Yes, this tip is that simple. Read the sticker, if the AFUE (annual fuel utilization efficiency) rating is 90 or over then you have high efficiency. 80 to 90 is standard efficiency and anything under 80 is just poor efficiency in my opinion.

Often times the Energy Guide label on furnaces is torn off, scratched, or painted over. If that's the case then try the next tip.

Tip #2 Exhaust Pipes..... Plastic Pipes Equal More Heat In The House:

Take a look at the exhaust pipes on the furnace, are they white plastic (pvc) or black plastic (abs)? If so, then you got yourself some high efficiency there, very nice! In a high efficiency furnace there is a secondary stainless steel heat exchanger. This heat exchanger will further scrub the exhaust of heat and pump that little bit extra back into the house. Not Bad! By the time the exhaust leaves the furnace it'll be around 100 degrees Fahrenheit which those plastic pipes can handle with ease. The pipes will also most likely exit the the house horizontally and not through the roof. Another advantage to the exhaust's low temps. Less holes in the roof equals less roof worries.

Unfortunately sometimes new furnaces are installed and exhaust pipes are used from the previous unit. In this case you could be looking at galvanized steel or a combination of that with brick and mortar. The next tip will help in that scenario.

Tip #3 Condensate Pump....... The Water Needs To Go Somewhere:

As exhaust from a high efficiency gas furnace cools in the secondary heat exchanger it creates a combination of water, carbon monoxide, and carbonic acid. Thus the need for it to be stainless steel. While the carbon monoxide will exhaust from the home as a gas the water and carbonic acid will not. These two byproducts must be removed from the furnace and the home. Typically this is done with a condensate pump located somewhere near the base of the furnace. If a pump is not present, look for a drain pipe on the furnace that most likely runs to a drain located in the foundation.


Wow, again who knew it could be so exciting. Use these tips when touring homes in your area to identify and understand the benefits of a high efficiency gas furnace.

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We are John and Catie Douville, real estate agents from the Tacoma area. We love exploring the South Sound and sharing our experiences through this blog. Sign up and never miss a post.

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