Is your furnace starting to show its age and you’re wondering what to replace it with? Or perhaps you’re looking at new construction and have similar questions.

It used to be fairly simple to install a standard furnace in a residence. Advances in technology, however, have brought the average homeowner more choices. Now you have to be a little savvier in knowing your home space so you can ask and get answers to the right questions.

Most people know that there are standard and high efficiency furnaces available but may not understand exactly what the difference is. Essentially, it has to do with AFUE: annual fuel utilization efficiency. What exactly is that, you ask? It measures how much of the heat generated by the furnace is actually used to heat your home. For a standard furnace, that’s 80%. (The rest is discharged as exhaust.) For a high efficiency furnace, the average is about 95%. Sounds pretty darn efficient, doesn’t it? You may be thinking, “Saves me money, is better for the environment? Sign me up!”

But hold on. A high efficiency furnace may be the best choice for you but as usual, there is more to the story. First of all, it depends where your furnace is or will be housed. A standard furnace uses the air around it in a vented space (usually a crawlspace, basement, or attic) in a process known as “open combustion.” If your furnace is in an unvented encapsulated crawlspace or attic sealed with spray foam, a high efficiency furnace would be a safety hazard here because not enough ambient air could cause a backdraft of carbon monoxide to enter your home!

That’s why high efficiency furnaces use a process called “sealed combustion.” Whether in a vented or unvented space, a furnace installer also installs a pipe to the outside of your home to bring combustion air in to the furnace, as well as a second pipe to drain the furnace’s condensation. (A high efficiency furnace has two heat exchangers, the second of which significantly cools the air, creating condensation. If you don’t want puddles of water on your floor, this condensation must be piped elsewhere!)

The higher cost of this type of furnace, along with the necessary installation of PVC piping, can raise the upfront cost by 25%-40% over a standard furnace. Whoa! But this, of course, needs to be balanced against the long-term increased energy savings of a high efficiency furnace. Also, remember that the piping is a one-time cost. If a high efficiency furnace is replaced with another high efficiency furnace at some point in the future, the original piping is already in place.

But wait, there are more considerations!

Today’s furnaces also come in single-stage, two-stage, and modulating designs. A single stage has only one setting: full blast. A two-stage design can use a lower setting for much of normal heating needs, reserving the higher stage for only when needed. A modulating unit is in tune with the interior conditions of home, adjusting accordingly. Every modulating design comes with a variable speed blower regulating the fan, an essential part of matching efficiency to comfort levels.

Is it possible that a standard two-stage modulating furnace could better meet your needs than a high efficiency single-stage furnace? Yes, it’s possible.

Do you plan to own your home for a long time, allowing you to take advantage of the increased energy savings over time? Do you plan on selling your home soon, where a high efficiency furnace could be a selling point? Either could be a very good reason to consider a high efficiency furnace.

As you can see, AFUE doesn’t tell the whole story. So many factors  –  how do you sort it all out?

The best way is to contact our HVAC service technicians who would be happy to help you make the best decision for your home based on your layout, comfort requirements, and budget.

When cold weather strikes, you want your home and more importantly your family to be prepared. With a safe and reliable Ruud gas furnace powering your home’s warmth, Ruud has got you covered for many winters to come.