What is a high-efficiency furnace?
A high-efficiency furnace has an total annual fuel usage efficiency (AFUE) rating of 90 to 97%. In other words, a furnace at the higher end of this range will convert 97% of the combusted natural gas to usable energy, with the remaining three percent exhausted to the outside.
By comparison, many older furnaces have an AFUE of only about 60%, meaning 40% of the fuel is wasted.
How do they work?
The majority of high-efficiency furnaces make use of a condensing method. Two heat exchangers pull sufficient heat from combustion gases that moisture in the gas condenses, releasing additional workable heat. The condensate is piped to a floor drain and exhaust gases are cool enough to be vented out a sidewall with a four-inch piece of plastic pipe, therefore doing away with the need for a chimney. Because the combustion in these types of furnaces is sealed, there is also no risk of carbon monoxide leakages.
Why should I purchase a high-efficiency furnace, isn’t a mid-efficient one good enough?
You may buy a mid-efficiency model (78-84% AFUE rating), however , mid-efficiency furnaces are up to 19% less efficient than a high-efficiency model and therefore will raise your operating expenses and greenhouse gas emissions. Depending on exactly what model you purchase and the actual amount of vent piping needed, a high-efficiency furnace can cost about a third more to purchase and install than a mid-efficiency design. Be aware that Natural Resources Canada has announced that, as of December 31, 2009, all brand new furnaces must have an AFUE rating of at least 90%.
A high-efficiency furnace (90% Annual Fuel Utilization Efficiency or higher) is a condensing furnaces and as such they were designed to utilize a second heat exchanger as a more efficient way of heating the air from condensed exhaust gases to reach higher efficiencies. What is more, a high-efficiency condensing furnace also requires specialized venting and draining systems to function accordingly. Unlike standard, 80% efficient furnaces which are non-condensing furnaces and therefore, don’t require the same kind of specialized materials to function.
Is it difficult to install a high-efficiency furnace?
Because of the growing popularity of high-efficiency furnaces in Canada, a substantial amount of companies now possess significant experience installing them. The layout and space considerations of your home will determine exactly what ductwork is needed. For instance, most high-efficiency furnaces are vented, by a four-inch pipe, to an outside wall and combustion air is drawn in through plastic pipes.
Will I notice any difference in the heating of my house?
A high-efficiency furnace runs quieter than a mid-efficiency furnace and should make your house more comfortable with its ability to maintain a more constant temperature. You may notice it cycles on and off more often, but for shorter time periods, than your old furnace.
What size should my high-efficiency furnace be?
Size is determined by the total building envelope heat loss, therefore a heat loss calculation should be done to accurately determine size (available from heating contractors). Quite often high efficiency furnaces are being installed that are too big for the actual heating requirements. An experienced contractor can properly size your new furnace. A high-efficiency model can generally be somewhat smaller, in BTU input, than an older or a mid-efficiency furnace.
The size of furnace you’ll need will be affected by the level of insulation and air tightness of your house. So it makes sense to plug those heat leaks and perhaps upgrade your insulation (especially under the roof, where you can get the most bang for your buck) before investing in a new furnace. By contrast, a too tightly-sealed house can affect air quality. Installing a fresh air intake or mechanical ventilation system will bring in and circulate fresh air, without causing drafts or heat loss.
How much money do you save with a high-efficiency furnace?
Some estimates suggest that, with a high-efficiency furnace, you can reduce your home gas bill by up to 35 to 45 percent (While operational). However, these numbers could be different for every household as ultimate furnace efficiency would depend on several factors external to your high efficiency unit. For Example, while installing a new furnace, the quality of the installation makes up a huge difference in the factual level of efficiency you’ll attain. A furnace must be sized to your home and installed correctly. If not, you’ll waste heat and won’t save as much money – plus your furnace will break down much sooner because it’s always turning on and off. Common installation problems include leaky ducts, improper air volume and incorrect-sized equipment and many other factors will affect the efficiency.
Do high-efficiency furnaces use more electricity?
When you choose to go with a high-efficiency furnace, the effect on the heating bill hits two ways. As with a high-efficiency furnace, you have a higher Annual Fuel Utilization Efficiency (AFUE); meaning you pay a lower gas bill. However, this does not mean that the overall energy bills are lower. Though, oftentimes this is dependent on the geographical location in which you live. Considering, the climate can impact how often the blower is run throughout the year and the more often the blower runs, the higher the electricity bill will be. High-efficiency furnaces use two sources of energy to heat your home. The first being the fuel that it burns, which is often natural gas or propane, and the second being the electricity that runs the blower.
Do high-efficiency furnaces run more often?
Yes! High-efficiency furnaces tend to run more often when compared to standard models, though for good reason. However, to fully understand why a high-efficiency furnace runs more often we must look at the different types of furnaces on the market. Typically, there are three main types of furnaces: single stage, two stage and modulating, each of which will have your furnace working for a different length of time throughout the day. Understanding which high-efficiency furnace you have is a great way to determine if your furnace is functioning normally or unusually. Not to mention, it also gives you a good indicator of how much energy you are potentially wasting. Although a high-efficiency furnace should be running at least 80% of the day if not longer.
Why do high-efficiency furnaces drain water?
High-efficiency furnaces are also known as condensing furnaces. Thus, it is normal for high-efficiency furnaces to create some form of condensation during their operation process. This is because they have two heat exchangers, which create water. As the two heat exchangers absorb so much heat that the exhaust gas changes from a gas state to a liquid state. Thus, creating condensation that is then drained through the condensate line. Note: to maintain a high efficiency rating your furnace must be properly serviced so it can efficiently drain the excess water that condensates. If there is a build-up of condensation, or any kind of leak or clog, the condensation can’t be carried out of your home and ends up pooling around your furnace system.
How should a high-efficiency furnace be vented?
If you’re thinking of installing a high-efficiency furnace in your home, be aware of the importance of high-efficiency venting. As there are several important aspects of high-efficiency venting, which require special venting and condensate drainage requirements. Most specifically, sidewall venting, and the use of PVC pipes. As proper sidewall venting requires installing separate vent pipes horizontally so that they went to the outdoors through a wall of your home. Additionally, these ventilation pipes should be isolated from the combustion chamber and sealed airtight to eliminate any possibility of combustion gas leakage. Moreover, these vents should be constructed so that any condensate in the pipes is able to drain backwards without freezing and drain directly into the floor drain or catch basin.
How do I know the furnaces I’m looking at are high-efficiency models?.
All high efficiency furnaces meet ENERGY STAR® standards and therefore will have an ENERGY STAR symbol on the furnace, on the packaging or promotional material. An EnerGuide label will indicate the furnace’s efficiency percentage.
Should I consider getting a variable-speed motor to run the fan of my new furnace?
Yes. Although the cost of a direct-current, variable-speed motors is higher, the electricity consumption will be at least 30% less than with a conventional motor.
A variable-speed motor is a high-efficiency motor due to the precise electronic controls allowing it to operate efficiently at any speed. A standard AC motor’s efficiency, on the other hand, drops off dramatically at lower speeds. Lower speed operation of the variable speed motor thus delivers savings, runs quieter, and provides more even temperature control throughout the home adding to occupant comfort.
How much maintenance does a high-efficiency furnace require?
A high-efficiency furnace should require no more maintenance than any other type of furnace. An annual maintenance check will help ensure your furnace is operating safely and at peak efficiency.