High Efficiency Furnaces

If you’re like most people, you’re concerned with getting the biggest bang for your buck when it comes to heating and cooling your home, and you may also be concerned about helping the environment by leaving a smaller carbon footprint. Energy efficiency is extremely important, which is why it’s become such a hot topic in recent years and why building codes have increasingly become more and more strict in dictating that homes be built to higher efficiency standards. An energy efficient home is more comfortable, less expensive (in the long run), and more valuable than a home that lacks efficiency, and less waste is always a good thing.

In this article, we’re going to focus on just one of many systems that determines the efficiency of a home: your furnace, and gas furnaces in particular. Many homeowners don’t know the efficiency of their furnace, let alone how it operates or what makes one heating system more efficient than another, and I hope to equip you with some basic knowledge so you can check your own system and ensure you’re getting the best value possible.

But first, a little history… for a very long time, homes were heated with low-efficiency, passive heating systems that had an efficiency rating of about 60% to 70% at best. This means that for every hundred dollars homeowners spent to heat their house, only about $60 to $70 was actually used to provide heat while $30 to $40 went out the chimney and was wasted. Not only that, but many homeowners had to perform manual labor to load, light and stoke their furnaces with a fuel source like wood or coal, which was manually delivered or obtained from the land. If that doesn’t sound like your cup of tea, be very thankful you’re alive today and benefiting from modern technology! There are actually plenty of people who still live this way and even prefer it, but the average American would rather not be burdened with so much work. For what it’s worth, though, I would argue that there is something fulfilling about doing things the old fashioned way. Still, I certainly prefer a high-efficiency and very low-maintenance heating system, just like the next guy!

Fast forward to the 1980’s, and some pretty revolutionary innovation began to take place. Lennox – a well known and reputable company – introduced the popular Pulse furnace, which achieved a much higher efficiency than what was even thought possible before. The company wasn’t shy about promoting it either, and the Pulse furnace may be the best marketed furnace of all time. Throughout the 80’s and 90’s, manufacturers learned various ways to design furnaces to use more of the heat they produce, and 80% to 90% became a more common efficiency standard. A furnace during that time period may have had an efficiency rating in the low 80’s but been considered high-efficiency by the standards at the time.

Today, many furnaces are rated at 95% or higher, which is leaps and bounds beyond the older, low-efficiency models that existed for decades. A high-efficiency furnace is a pretty remarkable piece of technology and saves homeowners a great deal of money. So, how do you know if your furnace is a high-efficiency model, and how exactly does it work?

Contrary to low and mid-efficiency furnaces that have one heat exchanger, a high-efficiency furnace has two. This allows the system to use more heat from combustion gases, and it also causes a good deal of condensation to form as the gases condense and form water vapor. For this reason, high-efficiency furnaces are also known as “condensing” furnaces. Because the exhaust gases are not as hot, the vent piping does not have to be metal as it does for older, less efficient systems. Instead, these furnaces use plastic vent pipes (usually PVC), which makes them easily identifiable. In fact, that’s one of the easiest ways (aside from looking at your furnace’s yellow efficiency sticker) to tell whether it’s rated at 90% or higher. If it has plastic white pipes it’s a high-efficiency furnace, and if it has a metal flue it’s not. The pipes for a high-efficiency furnace also don’t need to run through a chimney like metal flues, so you’ll typically see them protruding through a side wall of the home, often not far from the ground.

Like all good things, though, condensing furnaces do pose some potential drawbacks – namely the fact that they produce so much condensation. The water that is produced can wreak havoc on a furnace if it isn’t adequately contained and controlled, and it’s something we come across during inspections more often than you might think. The condensate must be contained so it can’t spill out anywhere inside the furnace, because this can lead to corrosion and eventual damage that destroys the system – especially if heat exchanger damage occurs. The condensate must also be drained away from the furnace, and the drain line has to be clean, unobstructed, and free of kinks so the water can easily move through the line. If the condensate doesn’t drain directly into a floor drain via simple gravity, it often first runs into a pump where it’s pumped upward and over to another drain, like a utility sink, and the pump is a mechanical part that is prone to eventual failure. Problems can arise any time, so periodic monitoring is a must if you have a high-efficiency furnace.

Sufficed to say, high-efficiency furnaces present a handful of potential problems, but they’re still well worth it as long as they are well looked after and maintained. Having $95 or more of every $100 you spend actually being used as intended is far, far better than only $80 or even $85. If you take the time to do some simple math and multiply that extra $10 or $15 for every $100 over many months and years, it will add up to a substantial savings very quickly.

Now, remember how I mentioned that older furnaces with an efficiency rating in the low 80’s were considered highly efficient for their time? That’s important to know because some manufacturers labeled them that way right on the furnace panel. Just the other day, we inspected a home with an oil furnace that had an efficiency rating of 81.4% that said “high efficiency” right on its front. By today’s standards, that furnace is not efficient, so be careful to check your own furnace beyond how it’s advertised – especially if it’s older. Likewise, some of the Lennox Pulse furnaces I mentioned (particularly those from the 1980’s) do have a known history of being susceptible to excess corrosion, so be sure to have yours checked and serviced at least annually by a qualified HVAC technician if you have one.

You may or may not know how efficient your current heating system is, and if you don’t I would strongly encourage you to check. If your furnace is older and not very efficient, you may want to consider upgrading to a more efficient system in the future. If you’re currently in the market for a new system and plan to stay in your home for a while, going the high-efficiency route is a no-brainer. You can also get highly efficient boilers, by the way, so this technology is not limited only to forced air systems. HTP and Buderus are a couple of popular high-efficiency manufacturers in the boiler world, although plenty of other companies also now offer great systems that will save you a lot of money and help improve the value and overall comfort of your home.

Check your furnace, calculate your potential savings, and make a plan to upgrade if you haven’t already. You won’t be sorry, but you’ll need to be diligent about maintaining your furnace often and as best as possible. That’s where a good HVAC company comes into play, so be sure to also establish a good relationship with an experienced and trusted professional to install and service your system.

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